World War II

World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing military alliances: the Allies and the Axis powers. World War II was a total war that directly involved more than 100 million personnel from more than 30 countries.

The major participants in the war threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. Aircraft played a major role in the conflict, enabling the strategic bombing of population centres and deploying the only two nuclear weapons ever used in war.

World War II was by far the deadliest conflict in human history; it resulted in 70 to 85 million fatalities, mostly among civilians. Tens of millions died due to genocides (including the Holocaust), starvation, massacres, and disease. In the wake of the Axis defeat, GermanyNazi Germany (officially known as the German Reich from 1933 until 1943, and the Greater German Reich from 1943 to 1945) was the German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a dictatorship. Under Hitler's rule, Germany quickly became a totalitarian state where nearly all aspects of life were controlled by the government.Germany and JapanThe Empire of Japan, also known as the Japanese Empire or Imperial Japan, was a historical nation-state and great power that existed from the Meiji Restoration in 1868 until the enactment of the post-World War II 1947 constitution and subsequent formation of modern Japan. Economic and political turmoil in the 1920s led to the rise of militarism, nationalism and totalitarianism eventually culminating in Japan's membership in the Axis alliance.Japan were occupied, and war crimes tribunals were conducted against German and Japanese leaders.

The causes of World War II are debated, but contributing factors included the Second Italo-Ethiopian War, Spanish Civil War, Second Sino-Japanese War, Soviet–Japanese border conflicts, rise of fascism in Europe and rising European tensions since World War IWorld War I, also known as the First World War, or the Great War, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. More than 70 million military personnel, including 60 million Europeans, were mobilized in one of the largest wars in history. The war drew in all the world's economic great powers, assembled in two opposing alliances: the Allies versus the Central Powers of Germany and Austria-Hungary. View World War I »World War I. World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded PolandPoland, officially the Republic of Poland, and in historical context referred to as the Third Polish Republic, is a country in Central Europe. The Kingdom of Poland emerged in 1025 and in 1569 cemented its longstanding association with Lithuania, thus forming the Polish–Lithuanian Commonwealth. It was one of the largest great powers of Europe at the time, with a uniquely liberal political system that adopted Europe's first modern constitution in 1791.Poland. The United Kingdom and FranceFrench Third Republic was the system of government adopted in France from 4 September 1870, when the Second French Empire collapsed during the Franco-Prussian War, until 10 July 1940, after the Fall of France during World War II led to the formation of the Vichy government. During the 19th and 20th centuries, the French colonial empire was the second largest colonial empire in the world only behind the British Empire.France subsequently declared war on Germany on 3 September. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet UnionSoviet Union, officially the Union of Soviet Socialist Republics (USSR), was a transcontinental country that spanned much of Eurasia from 1922 to 1991. The Soviet Union fall process began with growing unrest in the Union's various constituent national republics developing into an incessant political and legislative conflict between them and the central government. Estonia was the first Soviet republic to declare state sovereignty inside the Union.Soviet Union had partitioned Poland and marked out their "spheres of influence" across Finland, Estonia, Latvia, Lithuania and Romania. 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 ItalyThe Kingdom of Italy was a state that existed from 1861, when Victor Emmanuel II of Sardinia was proclaimed King of Italy, until 1946. The state resulted from a decades-long process, the Risorgimento, of consolidating the different states of the Italian Peninsula into a single state. That process was influenced by the Savoy-led Kingdom of Sardinia, which can be considered Italy's legal predecessor state.Italy and Japan (with other countries later). 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 EmpireThe British Empire, was composed of the dominions, colonies, protectorates, mandates, and other territories ruled or administered by the United Kingdom and its predecessor states. At its height it was the largest empire in history and, for over a century, was the foremost global power. By the start of the 20th century, Germany and the United States had begun to challenge Britain's economic lead.British Empire, with war in the Balkans, the aerial Battle of Britain, the Blitz of the United Kingdom, and the Battle of the Atlantic. On 22 June 1941, Germany led the European Axis powers in an invasion of the Soviet Union, opening the Eastern Front, the largest land theatre of war in history.

Japan, which aimed to dominate Asia and the Pacific, was at war with the Republic of China by 1937. In December 1941, Japan attacked American and British territories with near-simultaneous offensives against Southeast Asia and the Central Pacific, including an attack on the US fleet at Pearl Harbor which resulted in the United StatesThe United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country in North America. It is the world's third-largest country by both land and total area. The United States shares land borders with Canada to its north and with Mexico to its south. The national capital is Washington, D.C., and the most populous city and financial center is New York City.United States declaring war against Japan. The European Axis powers declared war on the United States in solidarity. Japan soon captured much of the western Pacific, but its advances were halted in 1942 after losing the critical Battle of Midway; later, Germany and Italy were defeated in North Africa and at Stalingrad in the Soviet Union. Key setbacks in 1943—including a series of German defeats on the Eastern Front, the Allied invasions of Sicily and the Italian mainland, and Allied offensives in the Pacific—cost the Axis powers their initiative and forced them 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 towards Germany and its allies. During 1944 and 1945, Japan suffered reversals in mainland Asia, while the Allies crippled the Japanese Navy and captured key western Pacific islands.

The war in Europe concluded with the liberation of German-occupied territories and the invasion of Germany by the Western Allies and the Soviet Union, culminating in the Fall of Berlin to Soviet troops, Hitler's suicide, and the German unconditional surrender on 8 May 1945. Following the refusal of Japan to surrender on the terms of the Potsdam Declaration (issued 26 July 1945), the United States dropped the first atomic bombs on the Japanese cities of Hiroshima on 6 August and Nagasaki on 9 August. Faced with an imminent invasion of the Japanese archipelago, the possibility of additional atomic bombings, and the Soviet Union's declared entry into the war against Japan on the eve of invading Manchuria, Japan announced on 10 August its intention to surrender, signing a surrender document on 2 September 1945.

World War II changed the political alignment and social structure of the globe. The United Nations (UN)United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizing the actions of nations. The UN was established after World War II with the aim of preventing future world wars, succeeding the League of Nations, which was characterized as ineffective.United Nations (UN) was established to foster international co-operation 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 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 and economic integration, especially in Europe, began as an effort to forestall future hostilities, end pre-war enmities and forge a sense of common identity.

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