How many people died in World War 1?

Estimates for the total number of casualties in the war vary, because many deaths went unrecorded. Most suggest that some 60 million people died in the war, including about 20 million military personnel and 40 million civilians.
Many of the civilians died because of deliberate genocide, massacres, mass-bombings, disease, and starvation.

World War II

World War II (often abbreviated to WWII or WW2), also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.

Japan, which aimed to dominate Asia and the Pacific, was at war with China by 1937, though neither side had declared war on the other. World War II is generally said to have begun on 1 September 1939, with the invasion of Poland by Germany and subsequent declarations on Germany by France and the United Kingdom. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Poland, Finland, Romania and the Baltic states. Following the onset of campaigns in North Africa and East Africa, and the fall of France in mid 1940, the war continued primarily between the European Axis powers and the British Empire. War in the Balkans, the aerial Battle of Britain, the Blitz, and the long Battle of the Atlantic followed. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history. This Eastern Front trapped the Axis, most crucially the German Wehrmacht, into a war of attrition. In December 1941, Japan launched a surprise attack on the United States and European colonies in the Pacific. Following an immediate U.S. declaration of war against Japan, supported by one from Great Britain, the European Axis powers quickly declared war on the U.S. in solidarity with their Japanese ally. Rapid Japanese conquests over much of the Western Pacific ensued, perceived by many in Asia as liberation from Western dominance and resulting in the support of several armies from defeated territories.

The Axis advance in the Pacific halted in 1942 when Japan lost the critical Battle of Midway; later, Germany and Italy were defeated in North Africa and then, decisively, at Stalingrad in the Soviet Union. Key setbacks in 1943, which included a series of German defeats on the Eastern Front, the Allied invasions of Sicily and Italy, and Allied victories in the Pacific, cost the Axis its initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned toward Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in Central China, South China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands.

The war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945. Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by fiat by the Allies and war crimes trials were conducted in the wake of the war both against the Germans and the Japanese.

World War II changed the political alignment and social structure of the globe. The United Nations (UN) was established to foster international co-operation and prevent future conflicts; the victorious great powers—China, France, the Soviet Union, the United Kingdom, and the United States—became the permanent members of its Security Council. The Soviet Union and United States emerged as rival superpowers, setting the stage for the nearly half-century long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia. Most countries whose industries had been damaged moved towards economic recovery and expansion. Political integration, especially in Europe, emerged as an effort to end pre-war enmities and create a common identity.

The start of the war in Europe is generally held to be 1 September 1939, beginning with the German invasion of Poland; the United Kingdom and France declared war on Germany two days later. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or even the Japanese invasion of Manchuria on 19 September 1931.

Others follow the British historian A.J.P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred simultaneously, and the two wars merged in 1941. This article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935. The British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the forces of Mongolia and the Soviet Union from May to September 1939.

The exact date of the war's end is also not universally agreed upon. It was generally accepted at the time that the war ended with the armistice of 14 August 1945 (V-J Day), rather than the formal surrender of Japan, which was on 2 September 1945 that officially ended the war in Asia. A peace treaty with Japan was signed in 1951. A treaty regarding Germany's future allowed the reunification of East and West Germany to take place in 1990 and resolved most post-World War II issues. No formal peace treaty between Japan and the Soviet Union was ever signed.

World War I had radically altered the political European map, with the defeat of the Central Powers—including Austria-Hungary, Germany, Bulgaria and the Ottoman Empire—and the 1917 Bolshevik seizure of power in Russia, which eventually led to the founding of the Soviet Union. Meanwhile, the victorious Allies of World War I, such as France, Belgium, Italy, Romania and Greece, gained territory, and new nation-states were created out of the collapse of Austria-Hungary and the Ottoman and Russian Empires.

To prevent a future world war, the League of Nations was created during the 1919 Paris Peace Conference. The organisation's primary goals were to prevent armed conflict through collective security, military and naval disarmament, and settling international disputes through peaceful negotiations and arbitration.

Despite strong pacifist sentiment after World War I, its aftermath still caused irredentist and revanchist nationalism in several European states. These sentiments were especially marked in Germany because of the significant territorial, colonial, and financial losses incurred by the Treaty of Versailles. Under the treaty, Germany lost around 13 percent of its home territory and all of its overseas possessions, while German annexation of other states was prohibited, reparations were imposed, and limits were placed on the size and capability of the country's armed forces.

The German Empire was dissolved in the German Revolution of 1918–1919, and a democratic government, later known as the Weimar Republic, was created. The interwar period saw strife between supporters of the new republic and hardline opponents on both the right and left. Italy, as an Entente ally, had made some post-war territorial gains; however, Italian nationalists were angered that the promises made by the United Kingdom and France to secure Italian entrance into the war were not fulfilled in the peace settlement. From 1922 to 1925, the Fascist movement led by Benito Mussolini seized power in Italy with a nationalist, totalitarian, and class collaborationist agenda that abolished representative democracy, repressed socialist, left-wing and liberal forces, and pursued an aggressive expansionist foreign policy aimed at making Italy a world power, promising the creation of a "New Roman Empire".

Adolf Hitler, after an unsuccessful attempt to overthrow the German government in 1923, eventually became the Chancellor of Germany in 1933. He abolished democracy, espousing a radical, racially motivated revision of the world order, and soon began a massive rearmament campaign. Meanwhile, France, to secure its alliance, allowed Italy a free hand in Ethiopia, which Italy desired as a colonial possession. The situation was aggravated in early 1935 when the Territory of the Saar Basin was legally reunited with Germany and Hitler repudiated the Treaty of Versailles, accelerated his rearmament programme, and introduced conscription.

The United Kingdom, France and Italy formed the Stresa Front in April 1935 in order to contain Germany, a key step towards military globalization; however, that June, the United Kingdom made an independent naval agreement with Germany, easing prior restrictions. The Soviet Union, concerned by Germany's goals of capturing vast areas of Eastern Europe, drafted a treaty of mutual assistance with France. Before taking effect though, the Franco-Soviet pact was required to go through the bureaucracy of the League of Nations, which rendered it essentially toothless. The United States, concerned with events in Europe and Asia, passed the Neutrality Act in August of the same year.

Hitler defied the Versailles and Locarno treaties by remilitarising the Rhineland in March 1936, encountering little opposition due to appeasement. In October 1936, Germany and Italy formed the Rome–Berlin Axis. A month later, Germany and Japan signed the Anti-Comintern Pact, which Italy would join in the following year.

The Kuomintang (KMT) party in China launched a unification campaign against regional warlords and nominally unified China in the mid-1920s, but was soon embroiled in a civil war against its former Chinese Communist Party allies and new regional warlords. In 1931, an increasingly militaristic Empire of Japan, which had long sought influence in China as the first step of what its government saw as the country's right to rule Asia, used the Mukden Incident as a pretext to launch an invasion of Manchuria and establish the puppet state of Manchukuo.

China appealed to the League of Nations to stop the Japanese invasion of Manchuria. Japan withdrew from the League of Nations after being condemned for its incursion into Manchuria. The two nations then fought several battles, in Shanghai, Rehe and Hebei, until the Tanggu Truce was signed in 1933. Thereafter, Chinese volunteer forces continued the resistance to Japanese aggression in Manchuria, and Chahar and Suiyuan. After the 1936 Xi'an Incident, the Kuomintang and communist forces agreed on a ceasefire to present a united front to oppose Japan.

The Second Italo–Ethiopian War was a brief colonial war that began in October 1935 and ended in May 1936. The war began with the invasion of the Ethiopian Empire (also known as Abyssinia) by the armed forces of the Kingdom of Italy ("Regno d'Italia"), which was launched from Italian Somaliland and Eritrea. The war resulted in the military occupation of Ethiopia and its annexation into the newly created colony of Italian East Africa ("Africa Orientale Italiana", or AOI); in addition it exposed the weakness of the League of Nations as a force to preserve peace. Both Italy and Ethiopia were member nations, but the League did little when the former clearly violated Article X of the League's Covenant. The United Kingdom and France supported imposing sanctions on Italy for the invasion, but they were not fully enforced and failed to end the Italian invasion. Italy subsequently dropped its objections to Germany's goal of absorbing Austria.

When civil war broke out in Spain, Hitler and Mussolini lent military support to the Nationalist rebels, led by General Francisco Franco. The Soviet Union supported the existing government, the Spanish Republic. Over 30,000 foreign volunteers, known as the International Brigades, also fought against the Nationalists. Both Germany and the Soviet Union used this proxy war as an opportunity to test in combat their most advanced weapons and tactics. The Nationalists won the civil war in April 1939; Franco, now dictator, remained officially neutral during World War II but generally favoured the Axis. His greatest collaboration with Germany was the sending of volunteers to fight on the Eastern Front.

In July 1937, Japan captured the former Chinese imperial capital of Peking after instigating the Marco Polo Bridge Incident, which culminated in the Japanese campaign to invade all of China. The Soviets quickly signed a non-aggression pact with China to lend materiel support, effectively ending China's prior co-operation with Germany. From September to November, the Japanese attacked Taiyuan, engaged the Kuomintang Army around Xinkou, and fought Communist forces in Pingxingguan. Generalissimo Chiang Kai-shek deployed his best army to defend Shanghai, but, after three months of fighting, Shanghai fell. The Japanese continued to push the Chinese forces back, capturing the capital Nanking in December 1937. After the fall of Nanking, tens of thousands if not hundreds of thousands of Chinese civilians and disarmed combatants were murdered by the Japanese.

In March 1938, Nationalist Chinese forces won their first major victory at Taierzhuang but then the city of Xuzhou was taken by Japanese in May. In June 1938, Chinese forces stalled the Japanese advance by flooding the Yellow River; this manoeuvre bought time for the Chinese to prepare their defences at Wuhan, but the city was taken by October. Japanese military victories did not bring about the collapse of Chinese resistance that Japan had hoped to achieve; instead the Chinese government relocated inland to Chongqing and continued the war.

In the mid-to-late 1930s, Japanese forces in Manchukuo had sporadic border clashes with the Soviet Union and Mongolia. The Japanese doctrine of Hokushin-ron, which emphasised Japan's expansion northward, was favoured by the Imperial Army during this time. With the Japanese defeat at Khalkin Gol in 1939, the ongoing Second Sino-Japanese War and ally Nazi Germany pursuing neutrality with the Soviets, this policy would prove difficult to maintain. Japan and the Soviet Union eventually signed a Neutrality Pact in April 1941, and Japan adopted the doctrine of Nanshin-ron, promoted by the Navy, which took its focus southward, eventually leading to its war with the United States and the Western Allies.

In Europe, Germany and Italy were becoming more aggressive. In March 1938, Germany annexed Austria, again provoking little response from other European powers. Encouraged, Hitler began pressing German claims on the Sudetenland, an area of Czechoslovakia with a predominantly ethnic German population. Soon the United Kingdom and France followed the counsel of British Prime Minister Neville Chamberlain and conceded this territory to Germany in the Munich Agreement, which was made against the wishes of the Czechoslovak government, in exchange for a promise of no further territorial demands. Soon afterwards, Germany and Italy forced Czechoslovakia to cede additional territory to Hungary, and Poland annexed Czechoslovakia's Zaolzie region.

Although all of Germany's stated demands had been satisfied by the agreement, privately Hitler was furious that British interference had prevented him from seizing all of Czechoslovakia in one operation. In subsequent speeches Hitler attacked British and Jewish "war-mongers" and in January 1939 secretly ordered a major build-up of the German navy to challenge British naval supremacy. In March 1939, Germany invaded the remainder of Czechoslovakia and subsequently split it into the German Protectorate of Bohemia and Moravia and a pro-German client state, the Slovak Republic. Hitler also delivered the 20 March 1939 ultimatum to Lithuania, forcing the concession of the Klaipėda Region.

Greatly alarmed and with Hitler making further demands on the Free City of Danzig, the United Kingdom and France guaranteed their support for Polish independence; when Italy conquered Albania in April 1939, the same guarantee was extended to Romania and Greece. Shortly after the Franco-British pledge to Poland, Germany and Italy formalised their own alliance with the Pact of Steel. Hitler accused the United Kingdom and Poland of trying to "encircle" Germany and renounced the Anglo-German Naval Agreement and the German–Polish Non-Aggression Pact.

The situation reached a general crisis in late August as German troops continued to mobilise against the Polish border. In August 23, when tripartite negotiations about a military alliance between France, the United Kingdom and Soviet Union stalled, the Soviet Union signed a non-aggression pact with Germany. This pact had a secret protocol that defined German and Soviet "spheres of influence" (western Poland and Lithuania for Germany; eastern Poland, Finland, Estonia, Latvia and Bessarabia for the Soviet Union), and raised the question of continuing Polish independence. The pact neutralized the possibility of Soviet opposition to a campaign against Poland and assured that Germany would not have to face the prospect of a two-front war, as it had in World War I. Immediately after that, Hitler ordered the attack to proceed on 26 August, but upon hearing that the United Kingdom had concluded a formal mutual assistance pact with Poland, and that Italy would maintain neutrality, he decided to delay it.

In response to British requests for direct negotiations to avoid war, Germany made demands on Poland, which only served as a pretext to worsen relations. On 29 August, Hitler demanded that a Polish plenipotentiary immediately travel to Berlin to negotiate the handover of Danzig, and to allow a plebiscite in the Polish Corridor in which the German minority would vote on secession. The Poles refused to comply with the German demands, and on the night of 30–31 August in a stormy meeting with the British ambassador Neville Henderson, Ribbentrop declared that Germany considered its claims rejected.

On 1 September 1939, Germany invaded Poland after having staged several false flag border incidents as a pretext to initiate the attack. The Battle of Westerplatte is often described as the first battle of the war. The United Kingdom responded with an ultimatum to Germany to cease military operations, and on 3 September, after the ultimatum was ignored, France, the United Kingdom, Australia, and New Zealand declared war on Germany. This alliance was joined by South Africa (6 September) and Canada (10 September). The alliance provided no direct military support to Poland, outside of a cautious French probe into the Saarland. The Western Allies also began a naval blockade of Germany, which aimed to damage the country's economy and war effort. Germany responded by ordering U-boat warfare against Allied merchant and warships, which would later escalate into the Battle of the Atlantic.
On 8 September, German troops reached the suburbs of Warsaw. The Polish counter offensive to the west halted the German advance for several days, but it was outflanked and encircled by the "Wehrmacht". Remnants of the Polish army broke through to besieged Warsaw. On 17 September 1939, after signing a cease-fire with Japan, the Soviets invaded Eastern Poland under a pretext that the Polish state had ostensibly ceased to exist. On 27 September, the Warsaw garrison surrendered to the Germans, and the last large operational unit of the Polish Army surrendered on 6 October. Despite the military defeat, the Polish government never surrendered. A significant part of Polish military personnel evacuated to Romania and the Baltic countries; many of them would fight against the Axis in other theatres of the war. The Polish government in exile also established an Underground State and a resistance movement; in particular the Polish partisan Home Army would grow to become one of the war's largest resistance movements.

Germany annexed the western and occupied the central part of Poland, and the Soviet Union annexed its eastern part; small shares of Polish territory were transferred to Lithuania and Slovakia. On 6 October, Hitler made a public peace overture to the United Kingdom and France, but said that the future of Poland was to be determined exclusively by Germany and the Soviet Union. The proposal was rejected, and Hitler ordered an immediate offensive against France, which would be postponed until the spring of 1940 due to bad weather.

The Soviet Union forced the Baltic countries—Estonia, Latvia and Lithuania, the states that were in the Soviet "sphere of influence" under the Molotov-Ribbentrop pact—to sign "mutual assistance pacts" that stipulated stationing Soviet troops in these countries. Soon after, significant Soviet military contingents were moved there. Finland refused to sign a similar pact and rejected ceding part of its territory to the Soviet Union. The Soviet Union invaded Finland in November 1939, and the Soviet Union was expelled from the League of Nations. Despite overwhelming numerical superiority, Soviet military success was modest, and the Finno-Soviet war ended in March 1940 with minimal Finnish concessions.

In June 1940, the Soviet Union forcibly annexed Estonia, Latvia and Lithuania, and the disputed Romanian regions of Bessarabia, Northern Bukovina and Hertza. Meanwhile, Nazi-Soviet political rapprochement and economic co-operation gradually stalled, and both states began preparations for war.

In April 1940, Germany invaded Denmark and Norway to protect shipments of iron ore from Sweden, which the Allies were attempting to cut off. Denmark capitulated after a few hours, and Norway was conquered within two months despite Allied support. British discontent over the Norwegian campaign led to the appointment of Winston Churchill as Prime Minister on 10May 1940.

On the same day, Germany launched an offensive against France. To circumvent the strong Maginot Line fortifications on the Franco-German border, Germany directed its attack at the neutral nations of Belgium, the Netherlands, and Luxembourg. The Germans carried out a flanking manoeuvre through the Ardennes region, which was mistakenly perceived by Allies as an impenetrable natural barrier against armoured vehicles. By successfully implementing new blitzkrieg tactics, the "Wehrmacht" rapidly advanced to the Channel and cut off the Allied forces in Belgium, trapping the bulk of the Allied armies in a cauldron on the Franco-Belgian border near Lille. The United Kingdom was able to evacuate a significant number of Allied troops from the continent by early June, although abandoning almost all of their equipment.

On 10 June, Italy invaded France, declaring war on both France and the United Kingdom. The Germans turned south against the weakened French army, and Paris fell to them on 14June. Eight days later France signed an armistice with Germany; it was divided into German and Italian occupation zones, and an unoccupied rump state under the Vichy Regime, which, though officially neutral, was generally aligned with Germany. France kept its fleet, which the United Kingdom attacked on 3July in an attempt to prevent its seizure by Germany.

The Battle of Britain began in early July with Luftwaffe attacks on shipping and harbours. The United Kingdom rejected Hitler's ultimatum, and the German air superiority campaign started in August but failed to defeat RAF Fighter Command. Due to this the proposed German invasion of Britain was postponed indefinitely on 17September. The German strategic bombing offensive intensified with night attacks on London and other cities in the Blitz, but failed to significantly disrupt the British war effort and largely ended in May 1941.

Using newly captured French ports, the German Navy enjoyed success against an over-extended Royal Navy, using U-boats against British shipping in the Atlantic. The British Home Fleet scored a significant victory on 27May 1941 by sinking the German battleship "Bismarck".

In November 1939, the United States was taking measures to assist China and the Western Allies, and amended the Neutrality Act to allow "cash and carry" purchases by the Allies. In 1940, following the German capture of Paris, the size of the United States Navy was significantly increased. In September the United States further agreed to a trade of American destroyers for British bases. Still, a large majority of the American public continued to oppose any direct military intervention in the conflict well into 1941. In December 1940 Roosevelt accused Hitler of planning world conquest and ruled out any negotiations as useless, calling for the United States to become an "arsenal of democracy" and promoting Lend-Lease programmes of aid to support the British war effort. The United States started strategic planning to prepare for a full-scale offensive against Germany.

At the end of September 1940, the Tripartite Pact formally united Japan, Italy and Germany as the Axis Powers. The Tripartite Pact stipulated that any country, with the exception of the Soviet Union, which attacked any Axis Power would be forced to go to war against all three. The Axis expanded in November 1940 when Hungary, Slovakia and Romania joined. Romania and Hungary would make major contributions to the Axis war against the Soviet Union, in Romania's case partially to recapture territory ceded to the Soviet Union.

In early June 1940 the Italian "Regia aeronautica" attacked and besieged Malta, a British possession. In late summer through early autumn Italy conquered British Somaliland and made an incursion into British-held Egypt. In October Italy attacked Greece, but the attack was repulsed with heavy Italian casualties; the campaign ended within days with minor territorial changes. Germany started preparation for an invasion of the Balkans to assist Italy, to prevent the British from gaining a foothold there, which would be a potential threat for Romanian oil fields, and to strike against the British dominance of the Mediterranean.

In December 1940, British Empire forces began counter-offensives against Italian forces in Egypt and Italian East Africa. The offensives were highly successful; by early February 1941 Italy had lost control of eastern Libya, and large numbers of Italian troops had been taken prisoner. The Italian Navy also suffered significant defeats, with the Royal Navy putting three Italian battleships out of commission by a carrier attack at Taranto and neutralising several more warships at the Battle of Cape Matapan.

Italian defeats prompted Germany to deploy an expeditionary force to North Africa, and at the end of March 1941 Rommel's Afrika Korps launched an offensive which drove back the Commonwealth forces. In under a month, Axis forces advanced to western Egypt and besieged the port of Tobruk.

By late March 1941 Bulgaria and Yugoslavia signed the Tripartite Pact. However, the Yugoslav government was overthrown two days later by pro-British nationalists. Germany responded with simultaneous invasions of both Yugoslavia and Greece, commencing on 6 April 1941; both nations were forced to surrender within the month. The airborne invasion of the Greek island of Crete at the end of May completed the German conquest of the Balkans. Although the Axis victory was swift, bitter and large-scale partisan warfare subsequently broke out against the Axis occupation of Yugoslavia, which continued until the end of the war.

In the Middle East, in May Commonwealth forces quashed an uprising in Iraq which had been supported by German aircraft from bases within Vichy-controlled Syria. Between June and July they invaded and occupied the French possessions Syria and Lebanon, with the assistance of the Free French.

With the situation in Europe and Asia relatively stable, Germany, Japan, and the Soviet Union made preparations. With the Soviets wary of mounting tensions with Germany and the Japanese planning to take advantage of the European War by seizing resource-rich European possessions in Southeast Asia, the two powers signed the Soviet–Japanese Neutrality Pact in April 1941. By contrast, the Germans were steadily making preparations for an attack on the Soviet Union, massing forces on the Soviet border.

Hitler believed that the United Kingdom's refusal to end the war was based on the hope that the United States and the Soviet Union would enter the war against Germany sooner or later. He therefore decided to try to strengthen Germany's relations with the Soviets, or failing that to attack and eliminate them as a factor. In November 1940, negotiations took place to determine if the Soviet Union would join the Tripartite Pact. The Soviets showed some interest, but asked for concessions from Finland, Bulgaria, Turkey, and Japan that Germany considered unacceptable. On 18 December 1940, Hitler issued the directive to prepare for an invasion of the Soviet Union.

On 22 June 1941, Germany, supported by Italy and Romania, invaded the Soviet Union in Operation Barbarossa, with Germany accusing the Soviets of plotting against them. They were joined shortly by Finland and Hungary. The primary targets of this surprise offensive were the Baltic region, Moscow and Ukraine, with the ultimate goal of ending the 1941 campaign near the Arkhangelsk-Astrakhan line, from the Caspian to the White Seas. Hitler's objectives were to eliminate the Soviet Union as a military power, exterminate Communism, generate "Lebensraum" ("living space") by dispossessing the native population and guarantee access to the strategic resources needed to defeat Germany's remaining rivals.

Although the Red Army was preparing for strategic counter-offensives before the war, "Barbarossa" forced the Soviet supreme command to adopt a strategic defence. During the summer, the Axis made significant gains into Soviet territory, inflicting immense losses in both personnel and materiel. By the middle of August, however, the German Army High Command decided to suspend the offensive of a considerably depleted Army Group Centre, and to divert the 2nd Panzer Group to reinforce troops advancing towards central Ukraine and Leningrad. The Kiev offensive was overwhelmingly successful, resulting in encirclement and elimination of four Soviet armies, and made possible further advance into Crimea and industrially developed Eastern Ukraine (the First Battle of Kharkov).

The diversion of three quarters of the Axis troops and the majority of their air forces from France and the central Mediterranean to the Eastern Front prompted the United Kingdom to reconsider its grand strategy. In July, the UK and the Soviet Union formed a military alliance against Germany The British and Soviets invaded neutral Iran to secure the Persian Corridor and Iran's oil fields. In August, the United Kingdom and the United States jointly issued the Atlantic Charter.

By October Axis operational objectives in Ukraine and the Baltic region were achieved, with only the sieges of Leningrad and Sevastopol continuing. A major offensive against Moscow was renewed; after two months of fierce battles in increasingly harsh weather the German army almost reached the outer suburbs of Moscow, where the exhausted troops were forced to suspend their offensive. Large territorial gains were made by Axis forces, but their campaign had failed to achieve its main objectives: two key cities remained in Soviet hands, the Soviet capability to resist was not broken, and the Soviet Union retained a considerable part of its military potential. The "blitzkrieg" phase of the war in Europe had ended.

By early December, freshly mobilised reserves allowed the Soviets to achieve numerical parity with Axis troops. This, as well as intelligence data which established that a minimal number of Soviet troops in the East would be sufficient to deter any attack by the Japanese Kwantung Army, allowed the Soviets to begin a massive counter-offensive that started on 5 December all along the front and pushed German troops west.

In 1939, the United States had renounced its trade treaty with Japan, and beginning with an aviation gasoline ban in July 1940, Japan became subject to increasing economic pressure. During this time, Japan launched its first attack against Changsha, a strategically important Chinese city, but was repulsed by late September. Despite several offensives by both sides, the war between China and Japan was stalemated by 1940. To increase pressure on China by blocking supply routes, and to better position Japanese forces in the event of a war with the Western powers, Japan invaded and occupied northern Indochina. Afterwards, the United States embargoed iron, steel and mechanical parts against Japan.

Chinese nationalist forces launched a large-scale counter-offensive in early 1940. In August, Chinese communists launched an offensive in Central China; in retaliation, Japan instituted harsh measures in occupied areas to reduce human and material resources for the communists. Continued antipathy between Chinese communist and nationalist forces culminated in armed clashes in January 1941, effectively ending their co-operation. In March, the Japanese 11th army attacked the headquarters of the Chinese 19th army but was repulsed during Battle of Shanggao. In September, Japan attempted to take the city of Changsha again and clashed with Chinese nationalist forces.

German successes in Europe encouraged Japan to increase pressure on European governments in Southeast Asia. The Dutch government agreed to provide Japan some oil supplies from the Dutch East Indies, but negotiations for additional access to their resources ended in failure in June 1941. In July 1941 Japan sent troops to southern Indochina, thus threatening British and Dutch possessions in the Far East. The United States, United Kingdom and other Western governments reacted to this move with a freeze on Japanese assets and a total oil embargo. At the same time, Japan was planning an invasion of the Soviet Far East, intending to capitalise off the German invasion in the west, but abandoned the operation after the sanctions.

Since early 1941 the United States and Japan had been engaged in negotiations in an attempt to improve their strained relations and end the war in China. During these negotiations Japan advanced a number of proposals which were dismissed by the Americans as inadequate. At the same time the United States, the United Kingdom, and the Netherlands engaged in secret discussions for the joint defence of their territories, in the event of a Japanese attack against any of them. Roosevelt reinforced the Philippines (an American protectorate scheduled for independence in 1946) and warned Japan that the United States would react to Japanese attacks against any "neighboring countries".

Frustrated at the lack of progress and feeling the pinch of the American-British-Dutch sanctions, Japan prepared for war. On 20 November a new government under Hideki Tojo presented an interim proposal as its final offer. It called for the end of American aid to China and for lifting the embargo on the supply of oil and other resources to Japan. In exchange Japan promised not to launch any attacks in Southeast Asia and to withdraw its forces from southern Indochina. The American counter-proposal of 26 November required that Japan evacuate all of China without conditions and conclude non-aggression pacts with all Pacific powers. That meant Japan was essentially forced to choose between abandoning its ambitions in China, or seizing the natural resources it needed in the Dutch East Indies by force; the Japanese military did not consider the former an option, and many officers considered the oil embargo an unspoken declaration of war.

Japan planned to rapidly seize European colonies in Asia to create a large defensive perimeter stretching into the Central Pacific. The Japanese would then be free to exploit the resources of Southeast Asia while exhausting the over-stretched Allies by fighting a defensive war. To prevent American intervention while securing the perimeter, it was further planned to neutralise the United States Pacific Fleet and the American military presence in the Philippines from the outset. On 7 December 1941 (8 December in Asian time zones), Japan attacked British and American holdings with near-simultaneous offensives against Southeast Asia and the Central Pacific. These included an attack on the American fleets at Pearl Harbor and the Philippines, landings in Thailand and Malaya, and the Battle of Hong Kong.

These attacks led the United States, United Kingdom, China, Australia and several other states to formally declare war on Japan, whereas the Soviet Union, being heavily involved in large-scale hostilities with European Axis countries, maintained its neutrality agreement with Japan. Germany, followed by the other Axis states, declared war on the United States in solidarity with Japan, citing as justification the American attacks on German war vessels that had been ordered by Roosevelt.

On 1 January 1942, the Allied Big Four—the Soviet Union, China, the United Kingdom and the United States—and 22 smaller or exiled governments issued the Declaration by United Nations, thereby affirming the Atlantic Charter, and agreeing to not to sign a separate peace with the Axis powers.

During 1942, Allied officials debated on the appropriate grand strategy to pursue. All agreed that defeating Germany was the primary objective. The Americans favoured a straightforward, large-scale attack on Germany through France. The Soviets were also demanding a second front. The British, on the other hand, argued that military operations should target peripheral areas to wear out German strength, leading to increasing demoralisation, and bolster resistance forces. Germany itself would be subject to a heavy bombing campaign. An offensive against Germany would then be launched primarily by Allied armour without using large-scale armies. Eventually, the British persuaded the Americans that a landing in France was infeasible in 1942 and they should instead focus on driving the Axis out of North Africa.

At the Casablanca Conference in early 1943, the Allies reiterated the statements issued in the 1942 Declaration, and demanded the unconditional surrender of their enemies. The British and Americans agreed to continue to press the initiative in the Mediterranean by invading Sicily to fully secure the Mediterranean supply routes. Although the British argued for further operations in the Balkans to bring Turkey into the war, in May 1943, the Americans extracted a British commitment to limit Allied operations in the Mediterranean to an invasion of the Italian mainland and to invade France in 1944.

By the end of April 1942, Japan and its ally Thailand had almost fully conquered Burma, Malaya, the Dutch East Indies, Singapore, and Rabaul, inflicting severe losses on Allied troops and taking a large number of prisoners. Despite stubborn resistance by Filipino and US forces, the Philippine Commonwealth was eventually captured in May 1942, forcing its government into exile. On 16 April, in Burma, 7,000 British soldiers were encircled by the Japanese 33rd Division during the Battle of Yenangyaung and rescued by the Chinese 38th Division. Japanese forces also achieved naval victories in the South China Sea, Java Sea and Indian Ocean, and bombed the Allied naval base at Darwin, Australia. In January 1942, the only Allied success against Japan was a Chinese victory at Changsha. These easy victories over unprepared US and European opponents left Japan overconfident, as well as overextended.

In early May 1942, Japan initiated operations to capture Port Moresby by amphibious assault and thus sever communications and supply lines between the United States and Australia. The planned invasion was thwarted when an Allied task force, centred on two American fleet carriers, fought Japanese naval forces to a draw in the Battle of the Coral Sea. Japan's next plan, motivated by the earlier Doolittle Raid, was to seize Midway Atoll and lure American carriers into battle to be eliminated; as a diversion, Japan would also send forces to occupy the Aleutian Islands in Alaska. In mid-May, Japan started the Zhejiang-Jiangxi Campaign in China, with the goal of inflicting retribution on the Chinese who aided the surviving American airmen in the Doolittle Raid by destroying air bases and fighting against the Chinese 23rd and 32nd Army Groups. In early June, Japan put its operations into action, but the Americans, having broken Japanese naval codes in late May, were fully aware of the plans and order of battle, and used this knowledge to achieve a decisive victory at Midway over the Imperial Japanese Navy.

With its capacity for aggressive action greatly diminished as a result of the Midway battle, Japan chose to focus on a belated attempt to capture Port Moresby by an overland campaign in the Territory of Papua. The Americans planned a counter-attack against Japanese positions in the southern Solomon Islands, primarily Guadalcanal, as a first step towards capturing Rabaul, the main Japanese base in Southeast Asia.

Both plans started in July, but by mid-September, the Battle for Guadalcanal took priority for the Japanese, and troops in New Guinea were ordered to withdraw from the Port Moresby area to the northern part of the island, where they faced Australian and United States troops in the Battle of Buna-Gona. Guadalcanal soon became a focal point for both sides with heavy commitments of troops and ships in the battle for Guadalcanal. By the start of 1943, the Japanese were defeated on the island and withdrew their troops. In Burma, Commonwealth forces mounted two operations. The first, an offensive into the Arakan region in late 1942, went disastrously, forcing a retreat back to India by May 1943. The second was the insertion of irregular forces behind Japanese front-lines in February which, by the end of April, had achieved mixed results.

Despite considerable losses, in early 1942 Germany and its allies stopped a major Soviet offensive in central and southern Russia, keeping most territorial gains they had achieved during the previous year. In May the Germans defeated Soviet offensives in the Kerch Peninsula and at Kharkov, and then launched their main summer offensive against southern Russia in June 1942, to seize the oil fields of the Caucasus and occupy Kuban steppe, while maintaining positions on the northern and central areas of the front. The Germans split Army Group South into two groups: Army Group A advanced to the lower Don River and struck south-east to the Caucasus, while Army Group B headed towards the Volga River. The Soviets decided to make their stand at Stalingrad on the Volga.

By mid-November, the Germans had nearly taken Stalingrad in bitter street fighting. The Soviets began their second winter counter-offensive, starting with an encirclement of German forces at Stalingrad, and an assault on the Rzhev salient near Moscow, though the latter failed disastrously. By early February 1943, the German Army had taken tremendous losses; German troops at Stalingrad had been forced to surrender, and the front-line had been pushed back beyond its position before the summer offensive. In mid-February, after the Soviet push had tapered off, the Germans launched another attack on Kharkov, creating a salient in their front line around the Soviet city of Kursk.

Exploiting poor American naval command decisions, the German navy ravaged Allied shipping off the American Atlantic coast. By November 1941, Commonwealth forces had launched a counter-offensive, Operation Crusader, in North Africa, and reclaimed all the gains the Germans and Italians had made. In North Africa, the Germans launched an offensive in January, pushing the British back to positions at the Gazala Line by early February, followed by a temporary lull in combat which Germany used to prepare for their upcoming offensives. Concerns the Japanese might use bases in Vichy-held Madagascar caused the British to invade the island in early May 1942. An Axis offensive in Libya forced an Allied retreat deep inside Egypt until Axis forces were stopped at El Alamein. On the Continent, raids of Allied commandos on strategic targets, culminating in the disastrous Dieppe Raid, demonstrated the Western Allies' inability to launch an invasion of continental Europe without much better preparation, equipment, and operational security.

In August 1942, the Allies succeeded in repelling a second attack against El Alamein and, at a high cost, managed to deliver desperately needed supplies to the besieged Malta. A few months later, the Allies commenced an attack of their own in Egypt, dislodging the Axis forces and beginning a drive west across Libya. This attack was followed up shortly after by Anglo-American landings in French North Africa, which resulted in the region joining the Allies. Hitler responded to the French colony's defection by ordering the occupation of Vichy France; although Vichy forces did not resist this violation of the armistice, they managed to scuttle their fleet to prevent its capture by German forces. The Axis forces in Africa withdrew into Tunisia, which was conquered by the Allies in May 1943.

In June 1943 the British and Americans began a strategic bombing campaign against Germany with a goal to disrupt the war economy, reduce morale, and "de-house" the civilian population. The firebombing of Hamburg was among the first attacks in this campaign, inflicting significant casualties and considerable losses on infrastructure of this important industrial center.

After the Guadalcanal Campaign, the Allies initiated several operations against Japan in the Pacific. In May 1943, Canadian and US forces were sent to eliminate Japanese forces from the Aleutians. Soon after, the United States, with support from Australian and New Zealand forces, began major operations to isolate Rabaul by capturing surrounding islands, and breach the Japanese Central Pacific perimeter at the Gilbert and Marshall Islands. By the end of March 1944, the Allies had completed both of these objectives, and had also neutralised the major Japanese base at Truk in the Caroline Islands. In April, the Allies launched an operation to retake Western New Guinea.

In the Soviet Union, both the Germans and the Soviets spent the spring and early summer of 1943 preparing for large offensives in central Russia. On 4 July 1943, Germany attacked Soviet forces around the Kursk Bulge. Within a week, German forces had exhausted themselves against the Soviets' deeply echeloned and well-constructed defences, and for the first time in the war Hitler cancelled the operation before it had achieved tactical or operational success. This decision was partially affected by the Western Allies' invasion of Sicily launched on 9 July, which, combined with previous Italian failures, resulted in the ousting and arrest of Mussolini later that month.

On 12 July 1943, the Soviets launched their own counter-offensives, thereby dispelling any chance of German victory or even stalemate in the east. The Soviet victory at Kursk marked the end of German superiority, giving the Soviet Union the initiative on the Eastern Front. The Germans tried to stabilise their eastern front along the hastily fortified Panther–Wotan line, but the Soviets broke through it at Smolensk and by the Lower Dnieper Offensives.

On 3 September 1943, the Western Allies invaded the Italian mainland, following Italy's armistice with the Allies. Germany with the help of fascists responded by disarming Italian forces that were in many places without superior orders, seizing military control of Italian areas, and creating a series of defensive lines. German special forces then rescued Mussolini, who then soon established a new client state in German-occupied Italy named the Italian Social Republic, causing an Italian civil war. The Western Allies fought through several lines until reaching the main German defensive line in mid-November.

German operations in the Atlantic also suffered. By May 1943, as Allied counter-measures became increasingly effective, the resulting sizeable German submarine losses forced a temporary halt of the German Atlantic naval campaign. In November 1943, Franklin D. Roosevelt and Winston Churchill met with Chiang Kai-shek in Cairo and then with Joseph Stalin in Tehran. The former conference determined the post-war return of Japanese territory and the military planning for the Burma Campaign, while the latter included agreement that the Western Allies would invade Europe in 1944 and that the Soviet Union would declare war on Japan within three months of Germany's defeat.

From November 1943, during the seven-week Battle of Changde, the Chinese forced Japan to fight a costly war of attrition, while awaiting Allied relief. In January 1944, the Allies launched a series of attacks in Italy against the line at Monte Cassino and tried to outflank it with landings at Anzio.

On 27 January 1944, Soviet troops launched a major offensive that expelled German forces from the Leningrad region, thereby ending the longest and most lethal siege in history. The following Soviet offensive was halted on the pre-war Estonian border by the German Army Group North aided by Estonians hoping to re-establish national independence. This delay slowed subsequent Soviet operations in the Baltic Sea region. By late May 1944, the Soviets had liberated Crimea, largely expelled Axis forces from Ukraine, and made incursions into Romania, which were repulsed by the Axis troops. The Allied offensives in Italy had succeeded and, at the expense of allowing several German divisions to retreat, on 4 June, Rome was captured.

The Allies had mixed success in mainland Asia. In March 1944, the Japanese launched the first of two invasions, an operation against British positions in Assam, India, and soon besieged Commonwealth positions at Imphal and Kohima. In May 1944, British forces mounted a counter-offensive that drove Japanese troops back to Burma, and Chinese forces that had invaded northern Burma in late 1943 besieged Japanese troops in Myitkyina. The second Japanese invasion of China aimed to destroy China's main fighting forces, secure railways between Japanese-held territory and capture Allied airfields. By June, the Japanese had conquered the province of Henan and begun a new attack on Changsha in the Hunan province.

On 6 June 1944 (known as D-Day), after three years of Soviet pressure, the Western Allies invaded northern France. After reassigning several Allied divisions from Italy, they also attacked southern France. These landings were successful, and led to the defeat of the German Army units in France. Paris was liberated on 25 August by the local resistance assisted by the Free French Forces, both led by General Charles de Gaulle, and the Western Allies continued to push back German forces in western Europe during the latter part of the year. An attempt to advance into northern Germany spearheaded by a major airborne operation in the Netherlands failed. After that, the Western Allies slowly pushed into Germany, but failed to cross the Ruhr river in a large offensive. In Italy, Allied advance also slowed due to the last major German defensive line.

On 22 June, the Soviets launched a strategic offensive in Belarus ("Operation Bagration") that destroyed the German Army Group Centre almost completely. Soon after that, another Soviet strategic offensive forced German troops from Western Ukraine and Eastern Poland. The Soviet advance prompted resistance forces in Poland to initiate several uprisings against the German occupation. However, the largest of these, in Warsaw and a national uprising in Slovakia, did not receive Soviet support and were subsequently suppressed by the Germans. The Red Army's strategic offensive in eastern Romania cut off and destroyed the considerable German troops there and triggered a successful coup d'état in Romania and in Bulgaria, followed by those countries' shift to the Allied side.

In September 1944, Soviet troops advanced into Yugoslavia and forced the rapid withdrawal of German Army Groups E and F in Greece, Albania and Yugoslavia to rescue them from being cut off. By this point, the Communist-led Partisans under Marshal Josip Broz Tito, who had led an increasingly successful guerrilla campaign against the occupation since 1941, controlled much of the territory of Yugoslavia and engaged in delaying efforts against German forces further south. In northern Serbia, the Red Army, with limited support from Bulgarian forces, assisted the Partisans in a joint liberation of the capital city of Belgrade on 20 October. A few days later, the Soviets launched a massive assault against German-occupied Hungary that lasted until the fall of Budapest in February 1945. Unlike impressive Soviet victories in the Balkans, bitter Finnish resistance to the Soviet offensive in the Karelian Isthmus denied the Soviets occupation of Finland and led to a Soviet-Finnish armistice on relatively mild conditions, although Finland was forced to fight their former allies.

By the start of July 1944, Commonwealth forces in Southeast Asia had repelled the Japanese sieges in Assam, pushing the Japanese back to the Chindwin River while the Chinese captured Myitkyina. In September 1944, Chinese force captured the Mount Song to reopen the Burma Road. In China, the Japanese had more successes, having finally captured Changsha in mid-June and the city of Hengyang by early August. Soon after, they invaded the province of Guangxi, winning major engagements against Chinese forces at Guilin and Liuzhou by the end of November and successfully linking up their forces in China and Indochina by mid-December.

In the Pacific, US forces continued to press back the Japanese perimeter. In mid-June 1944, they began their offensive against the Mariana and Palau islands, and decisively defeated Japanese forces in the Battle of the Philippine Sea. These defeats led to the resignation of the Japanese Prime Minister, Hideki Tojo, and provided the United States with air bases to launch intensive heavy bomber attacks on the Japanese home islands. In late October, American forces invaded the Filipino island of Leyte; soon after, Allied naval forces scored another large victory in the Battle of Leyte Gulf, one of the largest naval battles in history.

On 16 December 1944, Germany made a last attempt on the Western Front by using most of its remaining reserves to launch a massive counter-offensive in the Ardennes and along the French–German border to split the Western Allies, encircle large portions of Western Allied troops and capture their primary supply port at Antwerp to prompt a political settlement. By January, the offensive had been repulsed with no strategic objectives fulfilled. In Italy, the Western Allies remained stalemated at the German defensive line. In mid-January 1945, the Soviets and Poles attacked in Poland, pushing from the Vistula to the Oder river in Germany, and overran East Prussia. On 4 February, Soviet, British and US leaders met for the Yalta Conference. They agreed on the occupation of post-war Germany, and on when the Soviet Union would join the war against Japan.

In February, the Soviets entered Silesia and Pomerania, while Western Allies entered western Germany and closed to the Rhine river. By March, the Western Allies crossed the Rhine north and south of the Ruhr, encircling the German Army Group B. In early March, in attempts to protect her last oil reserves in Hungary and to retake Budapest, Germany launched the last major offensive, that was directed against Soviet troops near the lake Balaton. It two weeks, the offensive had been repulsed, the Soviets advanced to Vienna, and captured the city. In early April, Soviet troops captured Königsberg, while the Western Allies finally pushed forward in Italy and swept across western Germany capturing Hamburg and Nuremberg. American and Soviet forces met at the Elbe river on 25 April, leaving several unoccupied pockets in southern Germany and around Berlin.

Soviet and Polish forces stormed and captured Berlin in late April. In Italy, German forces surrendered on 29 April. On 30 April, the Reichstag was captured, signalling the military defeat of Nazi Germany, Berlin garrison surrendered on 2 May.

Several changes in leadership occurred during this period. On 12 April, President Roosevelt died and was succeeded by Harry S. Truman. Benito Mussolini was killed by Italian partisans on 28 April. Two days later, Hitler committed suicide in besieged Berlin, and he was succeeded by Grand Admiral Karl Dönitz.

Total and unconditional surrender was signed on 7 and 8 May, to be effective by the end of 8 May. German Army Group Centre resisted in Prague until 11 May.

In the Pacific theatre, American forces accompanied by the forces of the Philippine Commonwealth advanced in the Philippines, clearing Leyte by the end of April 1945. They landed on Luzon in January 1945 and recaptured Manila in March. Fighting continued on Luzon, Mindanao, and other islands of the Philippines until the end of the war. Meanwhile, the United States Army Air Forces launched a massive firebombing campaign of strategic cities in Japan in an effort to destroy Japanese war industry and civilian morale. A devastating bombing raid of 9–10 March was the deadliest conventional bombing raid in history.

In May 1945, Australian troops landed in Borneo, over-running the oilfields there. British, American, and Chinese forces defeated the Japanese in northern Burma in March, and the British pushed on to reach Rangoon by 3 May. Chinese forces started a counterattack in the Battle of West Hunan that occurred between 6 April and 7 June 1945. American naval and amphibious forces also moved towards Japan, taking Iwo Jima by March, and Okinawa by the end of June. At the same time, American submarines cut off Japanese imports, drastically reducing Japan's ability to supply its overseas forces.

On 11 July, Allied leaders met in Potsdam, Germany. They confirmed earlier agreements about Germany, and reiterated the demand for unconditional surrender of Japan, specifically stating that "the alternative for Japan is prompt and utter destruction". During this conference, the United Kingdom held its general election, and Clement Attlee replaced Churchill as Prime Minister.

The Allied call for unconditional surrender was rejected by the Japanese government, which believed it would be capable of negotiating for more favourable surrender terms. In early August, the USAAF dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. Between the two bombings, the Soviets, pursuant to the Yalta agreement, invaded Japanese-held Manchuria and quickly defeated the Kwantung Army, which was the largest Japanese fighting force, thereby persuading previously adamant Imperial Army leaders to accept surrender terms. The Red Army also captured the southern part of Sakhalin Island and the Kuril Islands. On 15 August 1945, Japan surrendered, with the surrender documents finally signed at Tokyo Bay on the deck of the American battleship USS "Missouri" on 2 September 1945, ending the war.

The Allies established occupation administrations in Austria and Germany. The former became a neutral state, non-aligned with any political bloc. The latter was divided into western and eastern occupation zones controlled by the Western Allies and the Soviet Union. A denazification programme in Germany led to the prosecution of Nazi war criminals in the Nuremberg trials and the removal of ex-Nazis from power, although this policy moved towards amnesty and re-integration of ex-Nazis into West German society.

Germany lost a quarter of its pre-war (1937) territory. Among the eastern territories, Silesia, Neumark and most of Pomerania were taken over by Poland, and East Prussia was divided between Poland and the Soviet Union, followed by the expulsion to Germany of the nine million Germans from these provinces, as well as three million Germans from the Sudetenland in Czechoslovakia. By the 1950s, one-fifth of West Germans were refugees from the east. The Soviet Union also took over the Polish provinces east of the Curzon line, from which 2 million Poles were expelled; north-east Romania, parts of eastern Finland, and the three Baltic states were incorporated into the Soviet Union.

In an effort to maintain world peace, the Allies formed the United Nations, which officially came into existence on 24 October 1945, and adopted the Universal Declaration of Human Rights in 1948 as a common standard for all member nations. The great powers that were the victors of the war—France, China, the United Kingdom, the Soviet Union and the United States—became the permanent members of the UN's Security Council. The five permanent members remain so to the present, although there have been two seat changes, between the Republic of China and the People's Republic of China in 1971, and between the Soviet Union and its successor state, the Russian Federation, following the dissolution of the Soviet Union in 1991. The alliance between the Western Allies and the Soviet Union had begun to deteriorate even before the war was over.

Germany had been "de facto" divided, and two independent states, the Federal Republic of Germany and the German Democratic Republic, were created within the borders of Allied and Soviet occupation zones. The rest of Europe was also divided into Western and Soviet spheres of influence. Most eastern and central European countries fell into the Soviet sphere, which led to establishment of Communist-led regimes, with full or partial support of the Soviet occupation authorities. As a result, East Germany, Poland, Hungary, Romania, Czechoslovakia, and Albania became Soviet satellite states. Communist Yugoslavia conducted a fully independent policy, causing tension with the Soviet Union.

Post-war division of the world was formalised by two international military alliances, the United States-led NATO and the Soviet-led Warsaw Pact. The long period of political tensions and military competition between them, the Cold War, would be accompanied by an unprecedented arms race and proxy wars.

In Asia, the United States led the occupation of Japan and administrated Japan's former islands in the Western Pacific, while the Soviets annexed Sakhalin and the Kuril Islands. Korea, formerly under Japanese rule, was divided and occupied by the Soviet Union in the North and the United States in the South between 1945 and 1948. Separate republics emerged on both sides of the 38th parallel in 1948, each claiming to be the legitimate government for all of Korea, which led ultimately to the Korean War.

In China, nationalist and communist forces resumed the civil war in June 1946. Communist forces were victorious and established the People's Republic of China on the mainland, while nationalist forces retreated to Taiwan in 1949. In the Middle East, the Arab rejection of the United Nations Partition Plan for Palestine and the creation of Israel marked the escalation of the Arab–Israeli conflict. While European powers attempted to retain some or all of their colonial empires, their losses of prestige and resources during the war rendered this unsuccessful, leading to decolonisation.

The global economy suffered heavily from the war, although participating nations were affected differently. The United States emerged much richer than any other nation, leading to a baby boom, and by 1950 its gross domestic product per person was much higher than that of any of the other powers, and it dominated the world economy. The UK and US pursued a policy of industrial disarmament in Western Germany in the years 1945–1948. Because of international trade interdependencies this led to European economic stagnation and delayed European recovery for several years.

Recovery began with the mid-1948 currency reform in Western Germany, and was sped up by the liberalisation of European economic policy that the Marshall Plan (1948–1951) both directly and indirectly caused. The post-1948 West German recovery has been called the German economic miracle. Italy also experienced an economic boom and the French economy rebounded. By contrast, the United Kingdom was in a state of economic ruin, and although receiving a quarter of the total Marshall Plan assistance, more than any other European country, it continued in relative economic decline for decades.

The Soviet Union, despite enormous human and material losses, also experienced rapid increase in production in the immediate post-war era. Japan experienced incredibly rapid economic growth, becoming one of the most powerful economies in the world by the 1980s. China returned to its pre-war industrial production by 1952.

Estimates for the total number of casualties in the war vary, because many deaths went unrecorded. Most suggest that some 60 million people died in the war, including about 20 million military personnel and 40 million civilians.
Many of the civilians died because of deliberate genocide, massacres, mass-bombings, disease, and starvation.

The Soviet Union lost around 27 million people during the war, 8.7 million military and 19 million civilian deaths. A quarter of the people in the Soviet Union were wounded or killed. Germany sustained 5.3 million military losses, mostly on the Eastern Front and during the final battles in Germany.

Of the total number of deaths in World War II, approximately 85 per cent—mostly Soviet and Chinese—were on the Allied side. Many of these deaths were caused by war crimes committed by German and Japanese forces in occupied territories. An estimated 11 to 17 million civilians died as a direct or as an indirect result of Nazi racist policies, including mass killing of around 6 million Jews, along with Roma, homosexuals, at least 1.9 million ethnic Poles and millions of other Slavs (including Russians, Ukrainians and Belarusians), and other ethnic and minority groups. Between 1941 and 1945, over 200,000 ethnic Serbs, along with gypsies and Jews, were persecuted and murdered by the Axis-aligned Croatian Ustaše in Yugoslavia. Also, over 100,000 Poles were massacred by the Ukrainian Insurgent Army in the Volhynia massacres, between 1943 and 1945. At the same time about 10,000–15,000 Ukrainians were killed by the Polish Home Army and another Polish units.

In Asia and the Pacific, between 3 million and more than 10 million civilians, mostly Chinese (estimated at 7.5 million), were killed by the Japanese occupation forces. The most infamous Japanese atrocity was the Nanking Massacre, in which fifty to three hundred thousand Chinese civilians were raped and murdered. Mitsuyoshi Himeta reported that 2.7 million casualties occurred during the "Sankō Sakusen". General Yasuji Okamura implemented the policy in Heipei and Shantung.

Axis forces employed biological and chemical weapons. The Imperial Japanese Army used a variety of such weapons during its invasion and occupation of China ("see Unit 731") and in early conflicts against the Soviets. Both the Germans and Japanese tested such weapons against civilians, and sometimes on prisoners of war.

The Soviet Union was responsible for the Katyn massacre of 22,000 Polish officers, and the imprisonment or execution of thousands of political prisoners by the NKVD, along with mass civilian deportations to Siberia, in the Baltic states and eastern Poland annexed by the Red Army.

The mass-bombing of cities in Europe and Asia has often been called a war crime, although no positive or specific customary international humanitarian law with respect to aerial warfare existed before or during World War II. The USAAF firebombed a total of 67 Japanese cities, killing 393,000 civilians and destroying 65% of built-up areas.

The German government led by Adolf Hitler and the Nazi Party was responsible for the Holocaust (killing approximately 6 million Jews), as well as for killing 2.7 million ethnic Poles and 4 million others who were deemed "unworthy of life" (including the disabled and mentally ill, Soviet prisoners of war, Romani, homosexuals, Freemasons, and Jehovah's Witnesses) as part of a programme of deliberate extermination. Soviet POWs were kept in especially unbearable conditions, and, although their extermination was not an official goal, 3.6 million Soviet POWs out of 5.7 died in Nazi camps during the war. In addition to concentration camps, death camps were created in Nazi Germany to exterminate people at an industrial scale. Nazi Germany extensively used forced labourers; about 12 million Europeans from German occupied countries were used as a slave work force in German agriculture and war economy.

The Soviet Gulag became a "de facto" system of deadly camps during 1942–43, when wartime privation and hunger caused numerous deaths of inmates, including foreign citizens of Poland and other countries occupied in 1939–40 by the Soviet Union, as well as Axis POWs. By the end of the war, most Soviet POWs liberated from Nazi camps and many repatriated civilians were detained in special filtration camps where they were subjected to NKVD evaluation, and a significant part of them were sent to the Gulag as real or perceived Nazi collaborators.

Japanese prisoner-of-war camps, many of which were used as labour camps, also had high death rates. The International Military Tribunal for the Far East found the death rate of Western prisoners was 27.1 per cent (for American POWs, 37 per cent), seven times that of POWs under the Germans and Italians. While 37,583 prisoners from the UK, 28,500 from the Netherlands, and 14,473 from the United States were released after the surrender of Japan, the number of Chinese released was only 56.

At least five million Chinese civilians from northern China and Manchukuo were enslaved between 1935 and 1941 by the East Asia Development Board, or "Kōain", for work in mines and war industries. After 1942, the number reached 10 million. In Java, between 4 and 10 million "rōmusha" (Japanese: "manual labourers"), were forced to work by the Japanese military. About 270,000 of these Javanese labourers were sent to other Japanese-held areas in South East Asia, and only 52,000 were repatriated to Java.

In Europe, occupation came under two forms. In Western, Northern, and Central Europe (France, Norway, Denmark, the Low Countries, and the annexed portions of Czechoslovakia) Germany established economic policies through which it collected roughly 69.5 billion reichmarks (27.8 billion US dollars) by the end of the war; this figure does not include the sizeable plunder of industrial products, military equipment, raw materials and other goods. Thus, the income from occupied nations was over 40 per cent of the income Germany collected from taxation, a figure which increased to nearly 40 per cent of total German income as the war went on.

In the East, the intended gains of "Lebensraum" were never attained as fluctuating front-lines and Soviet scorched earth policies denied resources to the German invaders. Unlike in the West, the Nazi racial policy encouraged extreme brutality against what it considered to be the "inferior people" of Slavic descent; most German advances were thus followed by mass executions. Although resistance groups formed in most occupied territories, they did not significantly hamper German operations in either the East or the West until late 1943.

In Asia, Japan termed nations under its occupation as being part of the Greater East Asia Co-Prosperity Sphere, essentially a Japanese hegemony which it claimed was for purposes of liberating colonised peoples. Although Japanese forces were originally welcomed as liberators from European domination in some territories, their excessive brutality turned local public opinion against them within weeks. During Japan's initial conquest it captured of oil (~5.5×10 tonnes) left behind by retreating Allied forces, and by 1943 was able to get production in the Dutch East Indies up to, 76 per cent of its 1940 output rate.

In Europe, before the outbreak of the war, the Allies had significant advantages in both population and economics. In 1938, the Western Allies (United Kingdom, France, Poland and British Dominions) had a 30 per cent larger population and a 30 per cent higher gross domestic product than the European Axis powers (Germany and Italy); if colonies are included, it then gives the Allies more than a 5:1 advantage in population and nearly 2:1 advantage in GDP. In Asia at the same time, China had roughly six times the population of Japan, but only an 89 per cent higher GDP; this is reduced to three times the population and only a 38 per cent higher GDP if Japanese colonies are included.

The United States provided about two-thirds of all the ordnance used by the Allies in terms of warships, transports, warplanes, artillery, tanks, trucks, and ammunition. Though the Allies' economic and population advantages were largely mitigated during the initial rapid blitzkrieg attacks of Germany and Japan, they became the decisive factor by 1942, after the United States and Soviet Union joined the Allies, as the war largely settled into one of attrition. While the Allies' ability to out-produce the Axis is often attributed to the Allies having more access to natural resources, other factors, such as Germany and Japan's reluctance to employ women in the labour force, Allied strategic bombing, and Germany's late shift to a war economy contributed significantly. Additionally, neither Germany nor Japan planned to fight a protracted war, and were not equipped to do so. To improve their production, Germany and Japan used millions of slave labourers; Germany used about 12 million people, mostly from Eastern Europe, while Japan used more than 18 million people in Far East Asia.

Aircraft were used for reconnaissance, as fighters, bombers, and ground-support, and each role was advanced considerably. Innovation included airlift (the capability to quickly move limited high-priority supplies, equipment, and personnel); and of strategic bombing (the bombing of enemy industrial and population centres to destroy the enemy's ability to wage war). Anti-aircraft weaponry also advanced, including defences such as radar and surface-to-air artillery. The use of the jet aircraft was pioneered and, though late introduction meant it had little impact, it led to jets becoming standard in air forces worldwide. Although guided missiles were being developed, they were not advanced enough to reliably target aircraft until some years after the war.

Advances were made in nearly every aspect of naval warfare, most notably with aircraft carriers and submarines. Although aeronautical warfare had relatively little success at the start of the war, actions at Taranto, Pearl Harbor, and the Coral Sea established the carrier as the dominant capital ship in place of the battleship. In the Atlantic, escort carriers proved to be a vital part of Allied convoys, increasing the effective protection radius and helping to close the Mid-Atlantic gap. Carriers were also more economical than battleships because of the relatively low cost of aircraft and their not requiring to be as heavily armoured. Submarines, which had proved to be an effective weapon during the First World War, were anticipated by all sides to be important in the second. The British focused development on anti-submarine weaponry and tactics, such as sonar and convoys, while Germany focused on improving its offensive capability, with designs such as the Type VII submarine and wolfpack tactics. Gradually, improving Allied technologies such as the Leigh light, hedgehog, squid, and homing torpedoes proved victorious.

Land warfare changed from the static front lines of trench warfare of World War I, which had relied on improved artillery that outmatched the speed of both infantry and cavalry, to increased mobility and combined arms. The tank, which had been used predominantly for infantry support in the First World War, had evolved into the primary weapon. In the late 1930s, tank design was considerably more advanced than it had been during World War I, and advances continued throughout the war with increases in speed, armour and firepower. At the start of the war, most commanders thought enemy tanks should be met by tanks with superior specifications. This idea was challenged by the poor performance of the relatively light early tank guns against armour, and German doctrine of avoiding tank-versus-tank combat. This, along with Germany's use of combined arms, were among the key elements of their highly successful blitzkrieg tactics across Poland and France. Many means of destroying tanks, including indirect artillery, anti-tank guns (both towed and self-propelled), mines, short-ranged infantry antitank weapons, and other tanks were used. Even with large-scale mechanisation, infantry remained the backbone of all forces, and throughout the war, most infantry were equipped similarly to World War I. The portable machine gun spread, a notable example being the German MG34, and various submachine guns which were suited to close combat in urban and jungle settings. The assault rifle, a late war development incorporating many features of the rifle and submachine gun, became the standard postwar infantry weapon for most armed forces.

Most major belligerents attempted to solve the problems of complexity and security involved in using large codebooks for cryptography by designing ciphering machines, the most well known being the German Enigma machine. Development of SIGINT ("sig"nals "int"elligence) and cryptanalysis enabled the countering process of decryption. Notable examples were the Allied decryption of Japanese naval codes and British Ultra, a pioneering method for decoding Enigma benefiting from information given to the United Kingdom by the Polish Cipher Bureau, which had been decoding early versions of Enigma before the war. Another aspect of military intelligence was the use of deception, which the Allies used to great effect, such as in operations Mincemeat and Bodyguard.

Other technological and engineering feats achieved during, or as a result of, the war include the world's first programmable computers (Z3, Colossus, and ENIAC), guided missiles and modern rockets, the Manhattan Project's development of nuclear weapons, operations research and the development of artificial harbours and oil pipelines under the English Channel.

Estimates for the total casualties of World War II vary, but most suggest that some 60 million people died in the war, including about 20 million soldiers and 40 million civilians. The Soviet Union lost around 27 million people during the war, about half of all World War II casualties. The largest number of civilian deaths in a single city was 1.2 million citizens dead during the 872-day Siege of Leningrad. Based on 1860 census figures, 8% of all white American males aged 13 to 50 died in the American Civil War. Of the 60 million European soldiers who were mobilized in World War I, 8 million were killed, 7 million were permanently disabled, and 15 million were seriously injured.

Effects of war

Post war effects are widely spread and can be long term or short term. Soldiers experience war differently than civilians, although either suffer in times of war, and women and children suffer unspeakable atrocities in particular. In the past decade, up to two million of those killed in armed conflicts were children. The widespread trauma caused by these atrocities and suffering of the civilian population is another legacy of these conflicts, the following creates extensive emotional and psychological stress. Present-day internal wars generally take a larger toll on civilians than state wars. This is due to the increasing trend where combatants have made targeting civilians a strategic objective. A state conflict is an armed conflict that occurs with the use of armed force between two parties, of which one is the government of a state. "The three problems posed by intra‐state conflict are the willingness of UN members, particularly the strongest member, to intervene; the structural ability of the UN to respond; and whether the traditional principles of peacekeeping should be applied to intra‐state conflict". Effects of war also include mass destruction of cities and have long lasting effects on a country's economy. Armed conflict have important indirect negative consequences on, infrastructure, public health provision, and social order. These indirect consequences are often overlooked and underappreciated.

Armed conflict is not clearly defined internationally. According to the Geneva Conventions of 1949, common article 2 states that "all cases of declared war or of any armed conflict that may arise between two or more high contracting parties, even if the state of war is not recognized, the convention shall also apply to all cases of partial or total occupation of the territory of a high contracting party even if the said occupation meets with no armed resistance". International humanitarian law works to protect the rights and dignity of civilians during peace and armed conflict with parties of the conflict having legally binding obligations concerning the rights of persons not involved in the conflict. Current day conflicts continue to occur with breaches of human rights and destruction of property continuing to happen due to state interests.

The economy may suffer devastating impacts during and after a time of war. According to Shank, "negative unintended consequences occur either concurrently with the war or develop as residual effects afterwards thereby impeding the economy over the longer term". In 2012 the economic impact of war and violence was estimated to be eleven percent of gross world product (GWP) or 9.46 trillion dollars. Everyday activities of a community or country are disrupted and property may be damaged. When people become misplaced, they cannot continue to work or keep their businesses open, causing damages to the economy of countries involved. A government may decide to direct money to fund war efforts, leaving other institutions with little or no available budget.

In some cases war has stimulated a country's economy (World War II is often credited with bringing America out of the Great Depression). According to the World Bank the event that conflicts subside in the country, and in the event that there is a transition to democracy the following will result in an increase economic growth by encouraging investment of the country and its people, schooling, economic restructuring, public-good provision, and reducing social unrest. Conflict very rarely has positive effects on an economy according to the world bank "Countries bordering conflict zones are facing tremendous budgetary pressure. The World Bank estimates that the influx of more than 630,000 Syrian refugees have cost Jordan over USD 2.5 billion a year. This amounts to 6 percent of GDP and one-fourth of government's annual revenues". One of the most commonly cited benefits for the economy is higher GDP growth. This has occurred throughout all of the conflict periods, other than in the Afghanistan and Iraq war period. Another benefit commonly mentioned is that WWII established the appropriate conditions for future growth and ended the great depression. In previous cases, such as the wars of Louis XIV, the Franco-Prussian War, and World War I, warfare serves only to damage the economy of the countries involved. For example, Russia's involvement in World War I took such a toll on the Russian economy that it almost collapsed and greatly contributed to the start of the Russian Revolution of 1917.

As a result of the Sri Lankan Civil War, Sri Lanka's military spending as a percentage of GDP, increased from 1.6 percent in 1983 to 3.5 in 2008 and reached an all-time peak at 5.9 percent of GDP in 1995 representing over 20 percent of the government's total spending. Until the war, arms were not nearly a significant amount of government spending and their defense personnel increased from 22,000 in 1989 to 213,000 in 2008. After the war began, however, arms were imported annually in response to increasing violence. By the year 2000, the Sri Lankan government's "import bill for arms was around $US 274 million", a record high during the war.

Destruction of infrastructure can create a catastrophic collapse in the social interrelated structure, infrastructure services, education and health care system. Destruction of schools and educational infrastructure have led to a decline in education among many countries affected by war. If certain infrastructural elements are significantly damaged or destroyed, it can cause serious disruption of the other systems such as the economy. This includes loss of certain transportation routes in a city which could make it impossible for the economy to function properly and also for people to be evacuated.

The labor force of the economy also changes with the effects of war. The labor force is affected in a multitude of ways most often due to the drastic loss of life, change in population, the labor force size shrinking due to the movement of refugees and displacement and the destruction of infrastructure which in turn allows for a deterioration of productivity.

When men head off to war, women take over the jobs they left behind. This causes an economic shift in certain countries because after the war these women usually want to keep their jobs. The shortage of labor force during the 1980–1988 Iran–Iraq War enabled women to enter fields of employment that had previously been closed to them and absorbed them into a large number of much-needed jobs. In "Women and Work in Iran", Povey points, "The Iran–Iraq war reduced the supply of male labor is one factor. The war increased the number of women seeking work or resisting exclusion. Many women even occupied important positions for the first time". This can also be seen in the Second Liberian Civil War, and in the Rwandan genocide. Women in both conflicts took over their husbands jobs due to the effects of the war, and received more economic equality as a result.

"International humanitarian law (IHL), also known as the laws of war and the law of armed conflict, is the legal framework applicable to situations of armed conflict and occupation. As a set of rules and principles it aims, for humanitarian reasons, to limit the effects of armed conflict".  International humanitarian law works to limit the effects of war and will protect the people who do not participate in such hostilities. Most wars have resulted in a significant loss of life. Conflict characterizes a major obstacle for the Millennium Development Goals (MDGs), particularly for the universal completion of primary education and gender equality in education. "The Millennium Development goals are the world's time-bound and quantified targets for addressing extreme poverty in its many dimensions-income poverty, hunger, disease, lack of adequate shelter, and exclusion-while promoting gender equality, education, and environmental sustainability. They are also basic human rights-the rights of each person on the planet to health, education, shelter, and security". There can be no doubt that armed conflict directly kills, injures, and harms more men than women in that combatants are predominantly male. Armed conflict has many indirect consequences such as on health and survival. "Armed conflict both generates conditions for increased morbidity and mortality".

During Napoleon's retreat from Moscow, more French soldiers died of typhus than were killed by the Russians. Felix Markham thinks that 450,000 crossed the Neman on 25 June 1812, of whom less than 40,000 recrossed in anything like a recognizable military formation. More soldiers were killed from 1500–1914 by typhus than from all military action during that time combined. In addition, if it were not for the modern medical advances there would be thousands more dead from disease and infection.

Displacement or forced migration results most often during a time of war and can adversely affect both the community and an individual. When a war breaks out, many people flee their homes in fear of losing their lives and their families, and as a result, they become misplaced either internally or externally. Those who are internally displaced face a direct threat because they do not receive the rights that a refugee may receive and are not eligible for protection under an international system. Victims of internal displacements are symptoms of war that are often motivated by communal hatred based on ethnic background, race, or religious views. External displacement are individuals who are forced out of the borders of their country into another as seen with the Syrian Refugees. The following may have a severe economic impact on a country.

In 2015, 53 percent of refugees worldwide originated from Somalia, Afghanistan, and Syria. In a Global Trends Report by the UNHRC, approximately 65 million people around the world have been forced from their home. Out of this number, 21.3 million are refugees, over half of the demographic under the age of 18. Some of the top countries absorbing these displaced peoples are Pakistan (1.6 million), Lebanon (1.1 million), and Turkey (2.5 million). In times of violence, people are displaced from their homes and seek places where they are welcome, periodically meeting places they are not welcome.

In response to an influx of refugees and asylum seekers from countries such as Afghanistan, Iraq, and Sri Lanka, Australia initiated a controversial plan in 2001 titled the Pacific Solution which called for all asylum seekers arriving by boat to be sent to the small and barren island Nauru. Asylum seekers were housed in crowded tents and lived under a constant threat of running out of resources, especially water. Individuals were kept in the detention center until their refugee status was granted or denied. Chris Evans, former immigration minister stated the Pacific Solution as being “a cynical, costly and ultimately unsuccessful exercise,” and was ended under a newly elected Prime Minister Kevin Rudd in 2007. In February 2008, after the Pacific Solution was ended, the final members of a group of 82 refugees detained on Nauru were granted residency rights and resettled in Australia according to a humanitarian resettlement program.

In the case of the Sri Lankan Civil War, displacement had a high chance to impoverish those affected, but women and children were found to be the most vulnerable to the burden of displacement. A Sri Lankan female head of household earns less than a household that has a male head. After men and women became displaced, however, females lost 76% of their income and males lost 80%. While the lost income is within a relatively close percentage, females were more likely, on average to fall below the official poverty line. Male household by comparison were able to stay above the line even after becoming displaced. In a post-displacement setting, male headed households had more earned income than female headed households. Males benefit from manual labor, carpentry, masonry, and government services while females had earned their income from informal work. Informal work for females is more difficult in a post-displacement setting where they do not have access to the same tools as they did pre-displacement.

The Palestinian people have suffered from displacement as a result of armed conflict and the military occupation. The largest displacement caused due to war occurred in 1947, after the United Nations agreed to have Palestine divided into two states. It later became the Israeli decision that Palestinian refugees no longer were permitted to return to their lands unless it was to reunify a family. "Nearly one-third of the registered Palestine refugees, more than 1.5 million individuals, live in 58 recognized Palestine refugee camps in Jordan, Lebanon, the Syrian Arab Republic, the Gaza Strip and the West Bank, including East Jerusalem".

Oftentimes when a country is in an economic crisis there is an increase in poverty which results in the decline of education. Over half of the world’s children that are out of school are assessed to live in conflict-affected fragile states. According to the UNESCO report “The groups most negatively affected by conflict were those that suffered from multiple exclusion, for example based on gender, area of residence, household wealth, language, and ethnicity”. One predominantly damaging, effect of conflict on education is the proliferation of attacks on schools with children, teachers and school buildings become the targets of violence. During times of war teachers and students often suffer from death or displacement. This prevents the opening of schools and increases teachers absenteeism. In the case of Iraq, boys were pulled out of school to work for their families, and therefore the education gap for men and women shrank.

Conflict negatively impacts women and men, which often results in gender-specific difficulties that are not recognized or addressed by mainstream communities across the globe (Baden and Goetz, 1997). War impacts women differently as they are more likely to die from indirect causes as opposed to direct causes. "Women and girls suffered disproportionately during and after war, as existing inequalities were magnified, and social networks broke down, making them more vulnerable to sexual violence and exploitation, the Under-Secretary-General for Peacekeeping Operations". Men during war are more likely to die from direct causes such as direct violence. The Beijing Declaration and Platform for Action, made women and armed conflict one of most critical areas of concern. It stated that peace is directly linked to equality between men and women and to development post conflict (Beijing Platform for Action). Plumper found that most women live longer when they are in peacetime, when compared to a state that is in armed conflict the gender gap of life expectancy drastically decreases in the male to female ratio. The indirect effects of militarized conflicts' affect access to food, hygiene, health services, and clean water. Women suffer more harshly from the damage to the health as well as overall well being, other infrastructure damages, and the wider economic damage as well as from dislocation during and post-conflict. During a time of war women are often separated from their husbands or lose them as a cost of war. Because of this there is a dramatic economic cost effect on women causing many to bear the entire economic responsibility for their household.

Three of the most common things done by Israeli military occupation includes the apartheid wall, displacement of people, and house demolitions caused by bombings especially in Gaza. This has severe consequences on men and women. As the number of marital disputes rises after a house demolition, women are forced to look for work in order to support the livelihood of their families. Also, there is a large rise in domestic violence that leaves women more vulnerable. Palestinians, particularly women, are unable to access basic services because of the closeness to or route of the apartheid wall, resulting in everyday abuse and suffering as they pass through Israeli checkpoints in order to have such access and admittance.

During the Thirty Years' War in Europe, for example, the population of the German states was reduced by about 30%. The Swedish armies alone may have destroyed up to 2,000 castles, 18,000 villages and 1,500 towns in Germany, one-third of all German towns.

Estimates for the total casualties of World War II vary, but most suggest that some 60 million people died in the war, including about 20 million soldiers and 40 million civilians. The Soviet Union lost around 27 million people during the war, about half of all World War II casualties. The largest number of civilian deaths in a single city was 1.2 million citizens dead during the 872-day Siege of Leningrad. Based on 1860 census figures, 8% of all white American males aged 13 to 50 died in the American Civil War. Of the 60 million European soldiers who were mobilized in World War I, 8 million were killed, 7 million were permanently disabled, and 15 million were seriously injured.

When war strikes it ends up affecting government structures along with the people in power of the government.  Many times, one regime is removed and new forms of government are put into place.  This can be seen in the Second Liberian Civil War where rebels had removed the current leader, Charles Taylor, and with the help of the United Nations deployed a new democratic form of government that stands for equal rights and even has a women president in Ellen Johnson Sirleaf.  This change in government was also apparent in Rwanda in 1993 when the genocide finally stopped.  The country had shifted from dictatorship to pure democracy and gave both men and women the right to vote.  The country also installed a quota system where a certain number of government seats must belong to women.  The country's quota was 30% of seats, however women now hold 55% of seats from their own merit.  These changes in government also changes the way the country behaves economically.

Some scholars, however, have argued that war can have a positive effect on political development.

Political scientist Jeffrey Herbst argues that interstate war is a requisite factor in the formation of strong states. Using Europe's history of state formation as his model, Herbst identifies interstate war as the factor that enabled states to effectively collect revenue and to generate a spirit of nationalism, two results that Herbst considers "crucial developments" in the formation of strong states. War increases both a leader's incentive to establish an efficient system of taxation and the population's willingness to assent to higher taxes. The existence of an external threat is also a powerful impetus for the development of a cooperative or unified state. Because the system of revenue collection, increased rate of taxation, and spirit of nationalism generally persist after war ends, war can have long-term consequences on a state's formation. This is particularly true of states in regions or periods of consistent warfare because states generally either adapted or were conquered. Herbst postulates that the stability of borders and lack of credible external threats between African states could result in "a new brand of states", those that will "remain permanently weak".

Charles Tilly, an American sociologist, political scientist, and historian, claims that within the context of European history, "war makes states." While the purposes of war were to expand territory and to check or overcome neighboring states, the process of war inadvertently engendered European-style state-building. War making resulted in state making in four ways:
War making and the extraction, protection, and state making that followed were interdependent. Tilly ultimately argues that the interactions between these four processes influenced the classic European state making experience.

The effects of conflict and its aftermath in Palestine reveals distinct types of disadvantages that worsen gender relations in both men and women. Increased militarization of the conflict and a rise in gender-based violence focused towards Palestinian as well as Israeli women are major ongoing issues happening in the conflict zone. The longstanding effects of Israeli occupation and policies of siege, confinement and confiscation of land have resulted in social as well as economic crisis for Palestinians. Consequently, the Israeli occupation remains a major problem for Palestinian women with regard to their advancement in labor, and participation in executive governmental bodies. In the light of an increasingly failing security and living conditions most efforts should be directed at everyday survival and creating a more stable environment for the Palestinian peoples. The pushing of gender issues should be at the peak of the political agenda.

One stark illustration of the effect of war upon economies is the Second World War. The Great Depression of the 1930s ended as nations increased their production of war materials to serve the war effort. The financial cost of World War II is estimated at about a $1.944 trillion U.S. dollars worldwide, making it the most costly war in capital as well as lives.

Property damage in the Soviet Union inflicted after the Axis invasion was estimated to a value of 679 billion rubles. The combined damage consisted of complete or partial destruction of 1,710 cities and towns, 70,000 villages/hamlets, 2,508 church buildings, 31,850 industrial establishments, 40,000 miles of railroad, 4100 railroad stations, 40,000 hospitals, 84,000 schools, and 43,000 public libraries.

The worst of the 20th century influenza pandemics was the 1918 pandemic, where between 20-40 percent of the world’s population became ill between 40-100 million people died. More people died of the so-called Spanish flu (caused by the H1N1 viral strain) pandemic in the single year of 1918 than during all four-years of the Black Death. The pandemic had devastating effects as disease spread along trade and shipping routes and other corridors of human movement until it had circled the globe. InIndia, the mortality rate reached 50 per 1,000 population. Arriving during the closing phase of the World War I, the pandemic impacted mobilized national armies. Half of U.S. soldiers who died in the "Great War," for example, were victims of influenza. It is estimated that almost ¾ of a million Americans died during the pandemic. In part, the death toll during the pandemic was caused by viral pneumonia characterized by extensive bleeding in the lungs resulting in suffocation. Many victims died within 48 hours of the appearance of the first symptom. It was not uncommon for people who appeared to be quite healthy in the morning to have died by sunset. Among those who survived the first several days, however, many died of secondary bacterial pneumonia. It has been argued that countless numbers of those who expired quickly from the disease were co-infected with tuberculosis, which would explain the notable plummet in TB cases after 1918.

Syndemic

A syndemic or synergistic epidemic is the aggregation of two or more concurrent or sequential epidemics or disease clusters in a population with biological interactions, which exacerbate the prognosis and burden of disease. The term was developed by Merrill Singer in the mid-1990s. Syndemics develop under health disparity, caused by poverty, stress, or structural violence and are studied by epidemiologists and medical anthropologists concerned with public health, community health and the effects of social conditions on health.

The syndemic approach departs from the biomedical approach to diseases to diagnostically isolate, study, and treat diseases as distinct entities separate from other diseases and independent of social contexts.

A syndemic is a synergistic epidemic. The term was developed by Merrill Singer in the mid-1990s, culminating in a 2009 textbook. Disease concentration, disease interaction, and their underlying social forces are the core concepts.
Disease co-occurrence, with or without interactions, is known as comorbidity and coinfection. The difference between "comorbid" and "syndemic" is per Mustanski et al. (2008:40) "comorbidity research tends to focus on the nosological issues of boundaries and overlap of diagnoses, while syndemic research focuses on communities experiencing co-occurring epidemics that additively increase negative health consequences." It is possible for two afflictions to be comorbid, but not syndemic i.e., the disorders are not epidemic in the studied population, or their co-occurrence is not accompanied by worsened health. Two or more diseases can be comorbid without interactions, or interaction occurs but it is beneficial, not deleterious. "Syndemic theory" seeks to draw attention to and provide a framework for the analysis of adverse disease interactions, including their causes and consequences for human life and well-being.

Diseases regularly interact and this interaction influences disease course, expression, severity, transmission, and diffusion. Interaction among diseases may be both indirect (changes caused by one disease that facilitate another through an intermediary) and direct (diseases act in direct tandem).

The term iatrogenesis means "brought forth by a healer" and refers to adverse effects on health caused by medical treatment. This is possible if medical treatment or medical research creates conditions that increase the likelihood that two or more diseases come together in a population. For example, if gene splicing unites two pathogenic agents and the resulting novel organism infects a population. One study suggests the possibility of iatriogenic syndemics. During a randomized, double-blind clinical trial testing the efficacy of the prototype HIV vaccine called V520 there appeared to be an increased risk for HIV infection among the vaccinated participants. Notably, participants immune to the common cold virus adenovirus type 5 had a higher risk of HIV infection. The vaccine was created using a replication-defective version of Ad5 as a carrier, or delivery vector, for three synthetically produced HIV genes. On November 6, 2007, Merck & Co. announced that research had been stopped suspecting the higher rate of HIV infection among individuals in the vaccinated was because the vaccine lowered defenses against HIV.

Various syndemics though not always labeled as such have been described in the literature, including the

Contact between Native Americans and Europeans during the Columbian Exchange led to lethal syndemics within the Native American population due to diseases introduced which the Native Americans had not encountered before and had not built-up immunity to.

An example of a syndemic from the 19th century can be found on the reservations on which Native Americans were confined with the closing of the U.S. frontier. It is estimated that in 1860 there were well over 10 million bison living on the American Plains. By the early 1880s, the last of the great herds of bison upon which Plains Indian peoples like the Sioux were dependent as a food source were gone. At the same time, after the U.S. military's defeat at the Battle of the Little Bighorn in 1876, there was a concerted effort to beat the Sioux into total submission. Thus, in 1872, Secretary of the Interior Columbus Delano stated: "as they become convinced that they can no longer rely upon the supply of game for their support, they will return to the more reliable source of subsistence [i.e., farming]." As a result, they were forced to give up their struggle for an independent existence on their own lands and take up reservation life at the mercy of government authority. Treaties that were signed with the Sioux in 1868 and 1876 stipulated that they would be provided with government annuities and provisions in payment for sections of their land and with the expectation among federal representatives that the Sioux would become farmers on individually held plots of land. The Sioux found themselves confined on a series of small reservations where they were treated as a conquered people. Moreover, the government reneged on its promises, food was insufficient and of low quality. Black Elk, a noted Sioux folk healer, told his biographer: "There was hunger among my people before I went across the big water [to Europe in 1886], because the Wasichus [whites] did not give us all the food they promised in the Black Hills treaty... But it was worse when I came back [1889]. My people looked pitiful… We could not eat lies and there was nothing we could do." Under extremely stressful conditions, with inadequate diets, and as victims of overt racism on the part of the registration agents appointed to oversee Indian reserves, the Sioux confronted infectious disease from contact with whites. knowledge about the epidemiology of the Sioux from this period is limited, James Mooney, an anthropologist and representative of the Bureau of Indian Affairs sent to investigate a possible Sioux rebellion, described the health situation on the reservation in 1896: "In 1888 their cattle had been diminished by disease. In 1889, their crops were a failure... Thus followed epidemics of measles, grippe [influenza], and whooping cough Pertussis, in rapid succession and with terrible fatal results…" Similarly, the "Handbook of American Indians" notes, "The least hopeful conditions in this respect prevail among the Dakota [Sioux] and other tribes of the colder northern regions, where pulmonary tuberculosis and scrofula are very common… Other more common diseases, are various forms of, bronchitis...pneumonia, pleurisy, and measles in the young. Whooping cough is also met with." Indian children were removed to white boarding schools and diagnosed with a wide range of diseases, including tuberculosis, trachoma, measles, smallpox, whooping cough, influenza, and pneumonia.

The Sioux were victims of a syndemic of interacting infectious diseases including the 1889–1890 flu pandemic, inadequate diet, and stressful and extremely disheartening life conditions, including outright brutalization with events like the massacre at Wounded Knee in 1890 and the murder of their leader Sitting Bull. While the official mortality rate on the reservation was between one and two percent, the death rate was probably closer to 10 percent.

There were three influenza pandemics during the 20th century that caused widespread illness, mortality, social disruption, and significant economic losses. These occurred in 1918, 1957, and 1968. In each case, mortality rates were determined primarily by five factors: the number of people who became infected, the virulence of the virus causing the pandemic, the speed of global spread, the underlying features and vulnerabilities of the most affected populations, and the effectiveness and timeliness of the prevention and treatment measures that were implemented.

The 1957 pandemic was caused by the Asian influenza virus (known as the H2N2 strain), a novel influenza variety to which humans had not yet developed immunities. The death toll of the 1957 pandemic is estimated to have been around two million globally, with approximately 70,000 deaths in the United States. A little over a decade later, the comparatively mild Hong Kong influenza pandemic erupted due to the spread of a virus strain (H3N2) that genetically was related to the more deadly form seen in 1957. The pandemic was responsible for about one million deaths around the world, almost 34,000 of which were in the United States. In both of these pandemics, death may not have been due only to the primary viral infection, but also to secondary bacterial infections among influenza patients; in short, they were caused by a viral/bacterial syndemic (but see Chatterjee 2007).

As a result of the floral changes produced by global warming, an escalation is occurring in global rates of allergies and asthma. Allergic diseases constitute the sixth leading cause of chronic illness in the United States, impacting 17 percent of the population. Asthma affects about 8 percent of the U.S. population, with rising tenndency, especially in low income, ethnic minority neighborhoods in cities. In 1980 asthma affected only about three percent of the U.S. population according to the U.S. CDC. Asthma among children has been increasing at an even faster pace than among adults, with the percentage of children with asthma going up from 3.6 percent in 1980 to 9 percent in 2005. Among ethnic minority populations, like Puerto Ricans the rate of asthma is 125 percent higher than non-Hispanic white people and 80 percent higher than non-Hispanic black people. The asthma prevalence among American Indians, Alaska Natives and black people is 25 percent higher than in white people.

Increases in asthma rates have occurred despite improvements in air quality produced by the passage and enforcement of clean air legislation, such as the U.S. Clean Air Act of 1963 and the Clean Air Act of 1990. existing legislation and regulation have not kept pace with changing climatic conditions and their health consequences. Compounding the problem of air quality is the fact that air-borne pollens have been found to attach themselves to diesel particles from truck or other vehicular exhaust floating in the air, resulting in heightened rates of asthma in areas where busy roads bisect densely populated areas, most notably in poorer inner city areas.

For every elevation of 10 μg/m3 in particulate matter concentration in the air a six percent increase in cardiopulmonary deaths occurs according to research by the American Cancer Society. Exhaust from the burning of diesel fuel is a complex mixture of vapors, gases, and fine particles, including over 40 known pollutants like nitrogen oxide and known or suspected carcinogenic substances such as benzene, arsenic, and formaldehyde. Exposure to diesel exhaust irritates the eyes, nose, throat and lungs, causing coughs, headaches, light headedness and nausea, while causing people with allergies to be more susceptible allergy triggers like dust or pollen. Many particles in disease fuel are so tiny they are able to penetrate deep into the lungs when inhaled. Importantly, diesel fuel particles appear to have even greater immunologic effects in the presence of environmental allergens than they do alone. "This immunologic evidence may help explain the epidemiologic studies indicating that children living along major trucking thoroughfares are at increased risk for asthmatic and allergic symptoms and are more likely to have respiratory dysfunction." according to Robert Pandya and co-workers.

The damaging effects of diesel fuel pollution goes beyond a synergistic role in asthma development. Exposure to a combination of microscopic diesel fuel particles among people with high blood cholesterol (i.e., low-density lipoprotein, LDL or "bad cholesterol") increases the risk for both heart attack and stroke above levels found among those exposed to only one of these health risks. According to André Nel, Chief of Nanomedicine at the David Geffen School of Medicine at UCLA, "When you add one plus one, it normally totals two... But we found that adding diesel particles to cholesterol fats equals three. Their combination creates a dangerous synergy that wreaks cardiovascular havoc far beyond what's caused by the diesel or cholesterol alone." Experimentation revealed that the two mechanisms worked in tandem to stimulate genes that promote cell inflammation, a primary risk for hardening and blockage of blood vessels (atherosclerosis) and, as narrowed arteries collect cholesterol deposits and trigger blood clots, for heart attacks and strokes as well.

A mathematical model is a simplified representation using mathematical language to describe natural, mechanical or social system dynamics. Epidemiological modelers unite several types of information and analytic capacity, including: 1) mathematical equations and computational algorithms; 2) computer technology; 3) epidemiological knowledge about infectious disease dynamics, including information about specific pathogens and disease vectors; and 4) research data on social conditions and human behavior. Mathematical modelling in epidemiology is now being applied to syndemics.

For example, modelling to quantify the syndemic effects of malaria and HIV in sub-Saharan Africa based on research in Kisumu, Kenya researchers found that 5% of HIV infections (or 8,500 cases of HIV since 1980) in Kisumu are the result of the higher HIV infectiousness of malaria-infected HIV patients. Additionally, their model attributed 10% of adult malaria episodes (or almost one million excess malaria infections since 1980) to the greater susceptibility of HIV infected individuals to malaria. Their model also suggests that HIV has contributed to the wider geographic spread of malaria in Africa, a process previously thought to be the consequence primarily of global warming. Modelling offers an enormously useful tool for anticipating future syndemics, including eco-syndemic, based on information about the spread of various diseases across the planet and the consequent co-infections and disease interactions that will result.

PopMod is a longitudinal population tool developed in 2003 that models distinct and possibly interacting diseases. Unlike other life-table population models, PopMod is designed to not assume the statistical independence of the diseases of interest. The PopMod has several intended purposes, including describing the time evolution of population health for standard demographic purposes (such as estimating healthy life expectancy in a population), and providing a standard measure of effectiveness for health interventions and cost-effectiveness analysis. PopMod is used as one of the standard tools of the World Health Organization’s (WHO) CHOICE (Choosing Interventions that are Cost-Effective) program, an initiative designed to provide national health policy makers in the WHO’s 14 epidemiological sub-regions around the world with findings on a range of health intervention costs and effects.

Although in Merrill Singer's conceptual work on syndemics the study of disease interaction is a central issue, most empirically based research studies have not used appropriate statistical models to do so. This problem was highlighted in a 2015 review. The majority (78%) used a statistical model, which provided no information about disease interaction. The methodological and public health consequences of this type of statistical model were further highlighted. While this criticism does not undermine the concept of disease concentration, it highlights a seriously flawed way of syndemics investigations.

First, there is a need for studies that examine the processes by which syndemics emerge, the specific sets of health and social conditions that foster multiple epidemics in a population and how syndemics function to produce specific kinds of health outcomes in populations.Second, there is a need to better understand processes of interaction between specific diseases with each other and with health-related factors like malnutrition, structural violence, discrimination, stigmatization, and toxic environmental exposure that reflect oppressive social relationships. There is a need to identify all of the ways, directly and indirectly, that diseases can interact and have, as a result, enhanced impact on human health. Third there is a need for the development of an eco-syndemic understanding of the ways in which global warming contributes to the spread of diseases and new disease interactions.
There is a need for a better understanding of how public health systems and communities can best respond to and limit the health consequences of syndemics. Systems are needed to monitor the emergence of syndemics and to allow early medical and public health responses to lessen their impact. Systematic ethno-epidemiological surveillance with populations subject to multiple social stressors must be one component of such a monitoring system.

Over 21 million people were killed or injured in World War I; in many cases, all of the men in one family were killed, numerous cities in Europe were destroyed, and family life throughout the world was greatly affected. While the United States suffered the fewest casualties, family life was still greatly affected as husbands were deployed and wives had to begin working. As the war draft suddenly removed many men from factory work, the factories began soliciting for women workers in traditionally male-dominated areas. Therefore, women had less time to spend at home with the children, as many of them would have before the war. As fathers, uncles, brothers, and grandfathers deployed in military service, women filled their places in factories and offices, changing the ways young children and teens received home nurturing. Additionally, women moving into new roles in society had lasting effects on children and family life after the war. President Woodrow Wilson stated, "We have made partners of the women in this war; shall we admit them only to a partnership of suffering and sacrifice and toil and not to a partnership of privilege and right?" As women began working in the factories, more of society began to realize the need for women's rights; while women had been granted suffrage (voting rights) to varying degrees in several states beginning in the late 19th century, they were now guaranteed full suffrage throughout the United States by the 19th Amendment to the United States Constitution passed in August, 1920. This also paved the way for the children of future generations by creating greater career opportunities for girls and women; as women gained a stronger voice, girls became more involved in the workforce and education and prepared for roles outside of the home. Additionally, family life was affected after the war as more and more women entered the work force, moving away from the traditional stay-at-home mother and housewife role.

Effect of World War I on children in the United States

Though the United States was in combat for only a matter of months, the reorganization of society had a great effect on American life. During World War I, daily life was affected as men were drafted and sent abroad, and women had to fill their places in the factories. Youth programs grew and developed in a response to aid the government with these new programs. During and after the war, life for children in the United States was greatly affected in a variety of ways.
More than 116,000 members of the U.S. military died in the war, far fewer than combatants from other countries. No one has estimated how many orphans resulted. Additionally, as the male workforce left for battle, mothers and sisters began working in factories to take their positions, and the family dynamic began to change; this affected children as they had less time to spend with family members and were expected to grow up faster and help with the war effort. Similarly, Woodrow Wilson called on children involved in youth organizations to help collect money for war bonds and stamps in order to raise money for the war effort. This was a way to mobilize public opinion and shame adults who did not donate. The Office of War Information and other agencies implemented programs and created posters and pamphlets to encourage war support.

The United States was involved in World War I for the last 19 months of the war (April 1917 to November 1918), 4,355,000 men were conscripted into service. By summer 1918, they were trained and shipped to France at the rate of 10,000 military personnel a day.

Meanwhile, every farm, town and city, and every economic sector, was mobilized for the war effort. Tens of millions of parents took war jobs or joined voluntary organizations such as the Red Cross. This involvement changed the course of the war and directly affected daily life, education, and family structures of children in the United States. The home front saw a systematic mobilization of the entire population and the entire economy to produce the soldiers, food supplies, munitions, and money needed to win the war. Although the United States entered the war in 1917, there had been very little planning, or even recognition of the problems that the British and other Allies had to solve on their homefronts. As a result, the level of confusion was high in the first 12 months, then efficiency took control.

After the United States entered the war, daily life was affected for most as men prepared for battle, women began working, and children and families had less time to spend together. The women and children did much more work than they used to. Children were affected as many of their fathers were killed or maimed in battle, and their mothers began working long hours in the factories. As the war progressed, technology advanced and industry boomed, enabling women to spend less time on household chores and more time outside of the home. The American family began to change as women started working more regularly, which affected the role of the child in American life.

Over the course of the war, the United States mobilized hundreds of thousands of men and endured an estimated 117,465 casualties. Of the men who survived and returned home, post-traumatic stress disorder created a major impact on society. During this time, and still today, post-traumatic stress (then more likely to be known as "shell shock") was not fully understood, but because of the traumatic nature of battle, many men were negatively affected after the war. Some men were forced to leave battle, which many people considered cowardice, and there were asylums throughout Europe housing men suffering from this condition. In some extreme cases, men were even shot for showing weakness. There are still people living today who lost family members because of this practice, which created lasting impacts on these children. Additionally, many of these men were teenagers when they left for war, and virtually all were under the age of 30; therefore many of these soldiers were barely out of childhood themselves.

Furthermore, because over a million young men were deployed overseas, marriage had to be postponed. In addition, a large number of the military personnel who returned home suffered from serious permanent injuries.

On the home front, domestic appliances were being created, alleviating the amount of time that women needed to spend on chores, so they had more time to work outside of the home. Additionally, this lessened the need for female servants, as things like laundry services and food preparation services became popular. Therefore, women were able to move into more traditionally male-dominated areas, as technology began to do the service jobs that women primarily were responsible for. Additionally, this showed young girls that they could eventually work outside of the home and more opportunities were available to them after they completed their education.

World War I altered education in the United States through curriculum changes with government pamphlets and required patriotism sessions. Even though the United States was only involved in World War I for a short period of time, the government instituted many programs for and changes to American education. During this war period, there was a strong focus on nationalism and patriotism, which significantly affected education. Woodrow Wilson and the United States government funded a series of pamphlets, posters, bulletins, and speeches, which promoted strong nationalism and anti-German sentiments. These forms of nationalist propaganda were used nationwide in public school districts and influenced students to remain loyal to the United States. These programs promoted things like volunteering with federal organizations such as the Reserve Officers' Training Corps (ROTC) and buying War Bonds to support the government.

Additionally, the government created several programs to help support education such as the Committee of Public Information (CPI), the National Education Association (NEA), and the Cardinal Principles of Secondary Education, all of which promoted nationalist movements and changes to education. For example, as part of the CPI and NEA programs, with the assistance of Woodrow Wilson, pamphlets were published advocating democracy and national patriotism in schools. These pamphlets also focused on a new movement of social efficacy, which strongly favored students growing as people and becoming involved, patriotic citizens. Another main goal of these educational programs was a move away from state education systems and toward a nationalized system of education, which would keep curriculums similar and promote a unified nation among students. For example, the national government changed textbooks to portray the American Revolution in a way that didn't make Britain look like the bad guys. This was important because the United States allied with Great Britain.

Starting as early as the elementary level, patriotic and pro-war lessons were instituted in public schools. They included things such as weekly fifteen-minute periods on patriotism for first and second grades. They stressed that teachers instruct the children so that they viewed the war in a positive manner and portrayed war in terms of celebrations, and victories, not destructive realities. An elementary pamphlet stated, "In teaching the war to young pupils, the appeal should be directed primarily to the imagination and to the emotions. It is not enough that our pupils shall be informed of the events of the war...Their imaginations must be awakened and their feelings aroused to an appreciation of the significance of the great happenings of the times." Therefore, starting at a very early level, students were taught that the war was a good thing and the importance of patriotism.

The patriotic sentiments were also carried out in secondary settings. Specific programs and in-school curricula targeted the patriotic development of children, especially teens. New history curricula introduced rewrote the story of the American past to de-emphasize the friction between the colonies and Britain, and to deconstruct historical American and German amity, to vilify the Germans. For example, every senior in high school received their own pamphlet in January 1918 called "Study of the Great War." This attempted to encourage enmity for Germany and emphasized the importance of an Allied victory. Things like the importance of the ROTC program were also stressed during this time. Nationalist posters and other forms of propaganda were placed in public areas throughout the country and again showed the importance of patriotism. Posters, like the Boy Scout poster shown below, depicted teenagers helping the war effort as being courageous and admired. This form of propaganda was especially influential on teenagers because most of them were trying to figure out their roles in society and desired to fit in; therefore, posters showing their peers serving their country and receiving recognition and respect, were particularly influential in persuading teenagers to join the war effort in whatever way they could.

After the war ended, nationalist movements changed to a larger focus on international peace. There were strong government movements toward peace and anti-war sentiments and the need to avoid further wars. Additionally, there was a focus on internationalization of higher education. For example, in 1920, the Belgian American Educational Foundation instituted a program with over 700 students, in which American students went to study in Belgium and vice versa in order to promote international understanding.

As a result of World War I, youth organizations such as the Boy Scouts and Camp Fire Girls greatly expanded, helping to raise money for the war effort.

Due to the large nationalist movement during World War I, many youth organizations were developed or expanded, including the Boy Scouts of America. During World War I, Woodrow Wilson placed a great importance on the Boy Scouts of America, asking them to encourage war support and educate the public sources about the importance of the war. They helped distribute the war pamphlets, helped sell war bonds and helped to drive nationalism and support for the war. Additionally, they were involved in many acts that helped the national government, such as locating black walnut to use in war materials and peach pits for gas masks. The Boy Scouts were involved in five Liberty Bond drives in which they helped sell Liberty Bonds to benefit the American Government. During the first campaign, they raised a total of $23,000,000 and in the second drive they collected $. For the third campaign, known as the "Wake Up, America" rally, beginning on April 27, 1918, 400,000 Boy Scouts embarked on a door to window program selling Liberty Bonds as well as war stamps. At the end of the five campaigns, the Boy Scouts raised $354,859,262 in bond subscriptions and $43,043,698 in war stamps. When a Boy Scout sold a bond or stamp, he would record the sale and send in a post card to his local post office, which would then forward it to the bonds and stamps, he would receive an "Ace Medal".

During World War I Camp Fire Girls helped to sell over one million dollars in Liberty Bonds and over $900,000 in Thrift Stamps; 55,000 girls helped to support French and Belgian orphans, and an estimated 68,000 girls earned honors by conservation of food.

After the conclusion of World War I, the United States and the rest of the world changed. Those who were children during World War I grew up to become the adults of World War II. These children were exposed to propaganda and indoctrinated to value strong nationalism and loyalty to the United States and its allies. Therefore, when World War II was on the forefront, many of the adults in the United States still harbored negative feelings toward the Germans because of their schooling during World War I.

Additionally, women were granted suffrage shortly after World War I. This was partly due to the fact that they had moved away from their traditional roles and filled the factory jobs that the men were forced to leave in order to serve in World War I. Women showed their importance in society, which fueled many women's rights movements post–World War I. The girls who were in school during World War I were also learning about the importance of nationalism, and saw their mothers fulfilling traditionally male-dominated roles. This desire for nationalism and exposure to wider opportunities helped to enable these girls to grow up and become involved in securing rights for themselves.

The total number of military and civilian casualties in World War I were about 40 million: estimates range from 15 to 19 million deaths and about 23 million wounded military personnel, ranking it among the deadliest conflicts in human history.

World War I casualties

The total number of deaths includes from 9 to 11 million military personnel. The civilian death toll was about 8 million, including about 6 million due to war-related famine and disease. The Triple Entente (also known as the Allies) lost about 6 million military personnel while the Central Powers lost about 4 million. At least 2 million died from diseases and 6 million went missing, presumed dead. This article lists the casualties of the belligerent powers based on official published sources.

About two-thirds of military deaths in World War I were in battle, unlike the conflicts that took place in the 19th century when the majority of deaths were due to disease. Nevertheless, disease, including the 1918 flu pandemic and deaths while held as prisoners of war, still caused about one third of total military deaths for all belligerents.

Casualty statistics for World War I vary to a great extent; estimates of total deaths range from 9 million to over 15 million. Military casualties reported in official sources list deaths due to all causes, including an estimated 7 to 8 million combat related deaths (killed or died of wounds) and another two to three million military deaths caused by accidents, disease and deaths while prisoners of war. Official government reports listing casualty statistics were published by the United States and Great Britain. These secondary sources published during the 1920s, are the source of the statistics in reference works listing casualties in World War I. This article summarizes the casualty statistics published in the official government reports of the United States and Great Britain as well as France, Italy, Belgium, Germany, Austria and Russia. More recently the research of the Commonwealth War Graves Commission (CWGC) has revised the military casualty statistics of the UK and its allies; they include in their listing of military war dead personnel outside of combat theaters and civilians recruited from Africa, the Middle East and China who provided logistical and service support in combat theaters. The casualties of these support personnel recruited outside of Europe were previously not included with British war dead, however the casualties of the Labour Corps recruited from the British Isles were included in the rolls of British war dead published in 1921. The methodology used by each nation to record and classify casualties was not uniform, a general caveat regarding casualty figures is that they cannot be considered comparable in all cases.

First World War civilian deaths are "hazardous to estimate" according to Michael Clodfelter who maintains that "the generally accepted figure of noncombatant deaths is 6.5 million." The figures listed below include about 6 million excess civilian deaths due to war related privations, that are often omitted from other compilations of World War I casualties. The war brought about malnutrition and disease caused by the U-boat Campaign and the Blockade of Germany which disrupted trade resulting in food shortages. The civilian deaths in the Ottoman Empire include the Armenian Genocide, Assyrian Genocide, and Greek Genocide. Civilian deaths due to the Spanish flu have been excluded from these figures, whenever possible. The figures do not include deaths during the Russian Civil War and the Turkish War of Independence.

The source of population data is: Haythornthwaite, Philip J., "The World War One Source Book" pp. 382–383

The war involved multi-ethnic empires such as Great Britain, France, Germany, Russia, Austria-Hungary and Turkey. Many ethnic groups in these territories were conscripted for military service. The casualties listed by modern borders are also included in the above table of figures for the countries that existed in 1914. The casualty figures by 1924 post war borders are rough estimates by Russian historian Vadim Erlikman in a 2004 handbook of human losses in the 20th century, the sources of his figures were published in the Soviet era and in post-Soviet Russia. According to the 1914–1918 Online Encyclopedia "In addition to losses suffered by African military personnel and the laborers supporting their operations, very large, but unknown numbers of African civilians perished during the war." They made an estimate of civilian losses in Africa of 750,000 based on the study by the Vadim Erlikman. They noted that Erlikman's figures are based on the work of the Russian demographer Boris Urlanis, they noted that these estimates were "imprecise" and "could be used to provide a frame of reference for further inquiry". The "Oxford History of World War One" notes that "In east and central Africa the harshness of the war resulted in acute shortages of food with famine in some areas, a weakening of populations, and epidemic diseases which killed hundreds of thousands of people and also cattle."
The following estimates of Austrian deaths, within contemporary borders, were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead 175,000: including military losses 120,000 with the Austro-Hungarian forces and POW deaths in captivity of 30,000. Civilian dead due to famine and disease were 25,000.
The following estimates of Belarusian deaths, within contemporary borders, were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead 130,000: including military losses 70,000 with the Russian forces. Civilian dead were 60,000.
The following estimates of Ukrainian deaths, within contemporary borders, were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead 590,000: including military losses 450,000,(Erlikman did not break out military losses between Austro-Hungarian and Russian armed forces). Civilian dead were 140,000.
The Belgian Congo was part of the Kingdom of Belgium during the war. A Russian historian Vadim Erlikman in a 2004 handbook of human losses in the 20th century based on sources published in the Soviet Union and Russia estimated a total of 155,000 deaths in the Belgian Congo during the war.
Czechoslovakia was part of Austro-Hungary during the war. The estimates of Czechoslovak deaths within 1991 borders were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead 185,000: including military losses 110,000 with the Austro-Hungarian forces and POW deaths in captivity of 45,000. Civilian dead due to famine and disease were 30,000. The Czechoslovak Legions fought with the armies of the Allies during the war.
Estonia was part of the Russian Empire during the war and about 100,000 Estonians served in the Russian Army. Of them about 10,000 were killed.
From 1809 Finland was an autonomous Grand Duchy in the Russian Empire until the end of 1917. In 1924 the Finnish government in a reply to a questionnaire from the International Labour Office, an agency of the League of Nations, reported 26,517 were dead and missing in World War I.

The following estimates of deaths, within contemporary borders, during World War I were made by a Russian historian Vadim Erlikman in a 2004 handbook of human losses in the 20th century. Erlikman's estimates are based on sources published in the Soviet Union and Russia.

The following estimates of Hungarian deaths, within contemporary borders, during World War I were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead 385,000: including military losses 270,000 with the Austro-Hungarian forces and POW deaths in captivity of 70,000. Civilian dead due to famine and disease were 45,000.
Ireland was a part of the UK during World War I. Five-sixths of the island left to form the Irish Free State, now the Republic of Ireland, in 1922. A total of 206,000 Irishmen served in the British forces during the war. The number of Irish deaths in the British Army recorded by the registrar general was 27,405. A significant number of these casualties were from what, in 1920, became Northern Ireland. While 49,400 soldiers died serving in Irish divisions (the 10th, 16th and 36th), although not all of the men serving in these divisions were natives of Ireland and many Irish who died in non-Irish regiments are not listed. For example, 29% of the casualties in the 16th Division were not natives of Ireland. Neither does it include Irish emigrants in Britain who enlisted there and are not categorised as Irish. Australia lists 4,731 of its first World War soldiers as having been born in Ireland and more than 19,000 Irish-born soldiers served in the Canadian Corps. According to research done by John Horne of Trinity College Dublin, there are at least 30,986 soldiers who were born in Ireland that died; however, that's considered a "conservative" estimate and is very likely to raise.
The losses of Portuguese Mozambique were estimated by a Russian historian Vadim Erlikman in a 2004 handbook of human losses in the 20th century. Erlikman's estimates are based on sources published in the Soviet Union and Russia. 52,000
Poland was territory of Germany, Austria-Hungary and partially annexed by Russia, from 1795 to 1918. By late 1915, Germany had complete control over modern-day Poland. A 2005 Polish study estimated 3,376,800 Poles were conscripted into the armed forces of these countries during World War I, an additional 300,000 were conscripted for forced labor by the Germans. The Russians and Austrians forcibly resettled 1.6 to 1.8 million persons from the war zone in Poland. According to Michael Clodfelter, Polish war dead were 1,080,000, whilst 200,000 Polish civilians were killed in the fighting on the Eastern Front; 870,000 men served in the German, Austrian and Russian armies. Another estimate made by a Russian historian in a 2004 handbook of human losses in the 20th century, put total Polish war dead at 640,000, including military losses of 270,000 Poles conscripted, civilian losses of 120,000 due to military operations and 250,000 caused by famine and disease. The ethnic Polish Blue Army served with the French Army. The ethnic Polish Legions fought as part of the Austro-Hungarian Army on the Eastern Front.
The territory of Transylvania was part of Austria-Hungary during World War I. The following estimates of Romanian deaths, within contemporary borders, during World War I were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead: 748,000, including military losses of 220,000 with the Romanian forces, 150,000 with the Austro-Hungarian forces and POW deaths in captivity of 48,000. Civilian dead were as follows due to famine and disease: 200,000, killed in military operations 120,000 and 10,000 dead in Austrian prisons.

Britain recruited Indian, Chinese, native South African, Egyptian and other overseas labour to provide logistical support in the combat theatres. Included with British casualties in East Africa are the deaths of 44,911 recruited labourers. The CWGC reports that nearly 2,000 workers from the Chinese Labour Corps are buried with British war dead in France.

The following estimates of British Empire colonial military deaths, within contemporary borders, during World War I were made by a Russian historian Vadim Erlikman in a 2004 handbook of human losses in the 20th century. Erlikman's estimates are based on sources published in the Soviet Union and Russia.

The following estimates are for Yugoslavia within the 1991 borders.

Slovenia, Croatia, Bosnia and Vojvodina (Now part of Serbia) were part of Austria-Hungary during World War I. Serbia, which included Macedonia, and Montenegro was an independent nation. The Yugoslav historian Vladimir Dedijer put the total losses of the Yugoslav lands at 1.9 million, of which 43% were from Serbia. The following estimates of Yugoslav deaths, within 1991 borders, during World War I were made by a Russian historian in a 2004 handbook of human losses in the 20th century. Total dead: 996,000 including military losses, 260,000 with the Serbian forces, 80,000 with the Austro-Hungarian forces, 13,000 with Montenegrin forces and POW deaths in captivity of 93,000. Civilian dead were as follows due to famine and disease: 400,000, killed in military operations: 120,000 and 30,000 dead in Austrian prisons or executed.
During World War I, the Nepalese army was expanded and six new regiments, totaling more than 20,000 troops—all volunteers—were sent to India, most of them to the North-West Frontier Province, to release British and Indian troops for service overseas. Simultaneously, the Nepalese government agreed to maintain recruitment at a level that would sustain the existing British Gurkha units and allow the establishment of additional ones. The battalions were increased to thirty-three with the addition of 55,000 new recruits and Gurkha units were placed at the disposal of the British high command for service on all fronts. Many volunteers were assigned to non-combat units, such as the Army Bearer Corps and the labour battalions but they also were in combat in France, Turkey, Palestine and Mesopotamia. The Rana prime ministers urged Nepalese males to fight in the war. Of the more than 200,000 Nepalese who served in the British army, there were some 20,000 Gurkha casualties included above with the British Indian Army.

East and Central Africa
AustraliaCanada

France

Greece

India (British)Italy Romania
 United KingdomUnited States
 Austria-Hungary

German Empire

Norway

SwedenThe source of population data is:

World War I casualties

East and Central Africa
AustraliaCanada

France

Greece

German Empire

Norway

SwedenThe source of population data is:

World War I casualties

East and Central Africa
AustraliaCanada

France

Greece

German Empire

Norway

SwedenThe source of population data is: