World War II, or the Second World War (1 September 1939 – 2 September 1945), was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many engaging in total war on an unprecedented scale. World War II was the deadliest conflict in history, causing the deaths of 60 to 75 million people, a majority of whom were civilians. Millions died as a result of massacres, starvation, disease, and genocides including the Holocaust. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.
The causes of World War II included unresolved tensions in the aftermath of World War I and the rise of fascism in Europe and militarism in Japan. Key events preceding the war included Japan's invasion of Manchuria in 1931, the Spanish Civil War, the outbreak of the Second Sino-Japanese War in 1937, and Germany's annexations of Austria and the Sudetenland. World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland, after which the United Kingdom and France declared war on Germany. Poland was also invaded by the Soviet Union in mid-September, and was partitioned between the two states under the Molotov–Ribbentrop Pact. In 1940, the Soviet Union annexed the Baltic states and parts of Finland and Romania, while Germany conquered Norway, Denmark, Belgium, Luxembourg, and the Netherlands. After the fall of France in June 1940, the war continued, mainly between Germany, now assisted by Fascist Italy, and the British Empire and British Commonwealth, with fighting in the Balkans, Mediterranean, Middle East, East Africa, the aerial Battle of Britain, the Blitz, and the naval Battle of the Atlantic. By mid-1941, Yugoslavia and Greece had also been defeated by Axis countries. In June 1941, Germany invaded the Soviet Union, opening the Eastern Front.
In December 1941, Japan attacked American and British territories in Asia and the Pacific, including Pearl Harbor in Hawaii, leading the United States to enter the war against the Axis. Japan conquered much of coastal China and Southeast Asia, but its advances in the Pacific were halted in June 1942 at the Battle of Midway. In early 1943, Axis forces were defeated in North Africa and at Stalingrad in the Soviet Union. An Allied invasion of Italy in July resulted in the fall of its fascist regime, and Allied offensives in the Pacific and the Soviet Union forced the Axis to retreat on all fronts. In 1944, the Western Allies invaded France at Normandy, opening a new front, and the Soviet Union advanced into Central Europe. Japan also suffered major setbacks, including the crippling of its navy by the United States, the loss of key Western Pacific islands, and defeats in Burma. The war in Europe concluded with the liberation of German-occupied territories and an invasion of Germany itself, which culminated in the fall of Berlin and Germany's unconditional surrender on 8 May 1945. On 6 and 9 August, the US dropped atomic bombs on Hiroshima and Nagasaki, followed by a Soviet invasion of Japanese-occupied Manchuria. Japan announced its unconditional surrender on 15 August and signed a surrender document on 2 September 1945.
World War II transformed the political, economic, and social structures of the world and established the foundation of international relations for the rest of the 20th century and into the 21st century. The United Nations was created to foster international cooperation and prevent future conflicts, with the victorious great powers—China, France, the Soviet Union, the United Kingdom, and the United States—becoming the permanent members of its Security Council. The Soviet Union and the United States emerged as rival superpowers, setting the stage for the Cold War. In the wake of Europe's devastation, the influence of its great powers waned, triggering the decolonisation of Africa and of Asia. Many countries whose industries had been damaged moved towards economic recovery and expansion.
Start and end dates
Most historians agree that World War II began with the German invasion of Poland on 1 September 1939 and the British and French declarations of war on Germany two days later. Dates for the beginning of the Pacific War include the start of the Second Sino-Japanese War on 7 July 1937, or the earlier Japanese invasion of Manchuria on 18 September 1931.Ghuhl, Wernar (2007) Imperial Japan's World War Two. Transaction Publishers, pp. 7, 30.Polmar, Norman; Allen, Thomas B. (1991) World War II: America at War, 1941–1945. Other proposed starting dates include the Italian invasion of Abyssinia on 3 October 1935.; ; Yisreelit, Hevrah Mizrahit (1965). Asian and African Studies, p. 191.For 1941 see ; Kellogg, William O. (2003) American History the Easy Way. Barron's Educational Series, p. 236. .There is also the viewpoint that both World War I and World War II were part of the same "European Civil War" or "Second Thirty Years' War": ; . 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. Others view the Spanish Civil War as the start of or prelude to World War II.
The 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 15 August 1945 (V-J Day), rather than with the formal surrender of Japan on 2 September 1945, which officially ended the war in Asia. A peace treaty between Japan and the Allies was signed in 1951. A 1990 treaty regarding Germany's future allowed the reunification of East and West Germany to take place. No formal peace treaty between Japan and the Soviet Union was ever signed, although the state of war between the two countries was terminated by the Soviet–Japanese Joint Declaration of 1956, which also restored full diplomatic relations between them.
Background
Aftermath of World War I
World War I radically altered the European political map. The most prominent nations of the Central Powers each lost territory in their respective peace treaties at the conclusion of the conflict. New nation-states were created out of the dissolution of the Austro-Hungarian, Ottoman, and Russian Empires.
To prevent a future world war, the League of Nations was established in 1920 by the Paris Peace Conference. The organisation's primary function was to prevent armed conflict through collective security, military, and naval disarmament, as well as settling international disputes through peaceful negotiations and arbitration.
Despite strong pacifist sentiment after World WarI, irredentist and revanchist nationalism had emerged in several European states. These sentiments were especially pronounced in Germany due to the significant territorial, colonial, and financial losses imposed by the Treaty of Versailles. Under the treaty, Germany lost around 13 per cent of its home territory and all 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.
Germany and Italy 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 political 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 when President Paul von Hindenburg and the Reichstag appointed him. The Nazis soon abolished parliamentary democracy, espousing a radical, racially motivated revision of the world order, and began a massive rearmament campaign. Following Hindenburg's death in 1934, Hitler proclaimed himself Führer of Germany. France, seeking to secure its alliance with Italy, 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.
European treaties The United Kingdom, France and Italy formed the Stresa Front in April 1935 to contain Germany, a key step towards military globalisation; 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 the policy of 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 joined the following year.
Asia The Kuomintang 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 (CCP) 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, staged the Mukden incident as a pretext to invade 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.: "Although some Chinese troops in the Northeast managed to retreat south, others were trapped by the advancing Japanese Army and were faced with the choice of resistance in defiance of orders, or surrender. A few commanders submitted, receiving high office in the puppet government, but others took up arms against the invader. The forces they commanded were the first of the volunteer armies." After the 1936 Xi'an Incident, the Kuomintang and CCP forces agreed on a ceasefire to present a united front to oppose Japan.
Pre-war events
Italian invasion of Ethiopia (1935)