|place = Europe, Pacific, Atlantic, South-East Asia, China, Middle East, Mediterranean, North Africa and Horn of Africa, briefly North and South America
|result = Allied victory
* Collapse of Nazi Germany
* Fall of Japanese and Italian Empires
* Creation of the United Nations
* Emergence of the United States and the Soviet Union as superpowers
* Beginning of the Cold War (more...).
| combatants_header = Participants
|commander1 = Main Allied leaders
|commander2 = Main Axis leaders
|casualties1 = Military dead:
Over 61,000,000 (1937–45)
|casualties2 = Military dead:
Over 12,000,000 (1937–45)
World War II (WWII or WW2), also known as the Second World War, was a global war that lasted from 1939 to 1945, though related conflicts began earlier. It involved the vast majority of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. In a state of "total war", the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, erasing the distinction between civilian and military resources. Marked by mass deaths of civilians, including the Holocaust (in which approximately 11 million people were killed) and the strategic bombing of industrial and population centres (in which approximately one million were killed, and which included the atomic bombings of Hiroshima and Nagasaki), it resulted in an estimated 50 million to 85 million fatalities. These made World War II the deadliest conflict in human history.〔.〕
The Empire of Japan aimed to dominate Asia and the Pacific and was already at war with the Republic of China in 1937,〔.〕 but the world war is generally said to have begun on 1 September 1939〔Axelrod, Alan (2007) ''Encyclopedia of World War II, Volume 1''. Infobase Publishing. pp. 659.〕 with the invasion of Poland by Germany and subsequent declarations of war 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. Based on 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. For a year starting in late June 1940, the United Kingdom and the British Commonwealth were the only Allied forces continuing the fight against the European Axis powers, with campaigns in North Africa and the Horn of Africa, the aerial Battle of Britain and the Blitz bombing campaign, as well as the long-running Battle of the Atlantic. In June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history, which trapped the major part of the Axis' military forces into a war of attrition. In December 1941, Japan attacked the United States and European territories in the Pacific Ocean, and quickly conquered much of the Western Pacific.
The Axis advance halted in 1942 when Japan lost the critical Battle of Midway, near Hawaii, and Germany was defeated in North Africa and then, decisively, at Stalingrad in the Soviet Union. In 1943, with a series of German defeats on the Eastern Front, the Allied invasion of Italy which brought about Italian surrender, and Allied victories in the Pacific, the Axis lost the initiative and undertook strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained all of its territorial losses and invaded Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in South Central China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands.
The war in Europe ended with an invasion of Germany by the Western Allies and the Soviet Union culminating in the capture of Berlin by Soviet and Polish troops and the subsequent 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 August and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, and the Soviet Union's declaration of war on Japan and invasion of Manchuria, Japan surrendered on 15 August 1945. Thus ended the war in Asia, cementing the total victory of the Allies.
World War II altered the political alignment and social structure of the world. The United Nations (UN) was established to foster international co-operation and prevent future conflicts. The victorious great powers—the United States, the Soviet Union, China, the United Kingdom, and France—became the permanent members of the United Nations Security Council. The Soviet Union and the United States emerged as rival superpowers, setting the stage for the Cold War, which lasted for the next 46 years. Meanwhile, the influence of European great powers waned, while the decolonisation of Asia and Africa began. Most countries whose industries had been damaged moved towards economic recovery. Political integration, especially in Europe, emerged as an effort to end pre-war enmities and to create a common identity.
The start of the war in Europe is generally held to be 1 September 1939,〔Weinberg, Gerhard L. (2005) ''A World at Arms: A Global History of World War II'' (2nd ed.). Cambridge University Press. pp. 6.〕〔Wells, Anne Sharp (2014) ''Historical Dictionary of World War II: The War against Germany and Italy''. Rowman & Littlefield Publishing. pp. 7.〕 beginning with the German invasion of Poland; Britain 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.〔Ghuhl, Wernar (2007) ''Imperial Japan's World War Two'' Transaction Publishers pg 7, pg. 30〕〔Polmar, Norman; Thomas B. Allen (1991) World War II: America at war, 1941-1945 ISBN 978-0394585307〕
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.〔; ; 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 ISBN 0-7641-1973-7.
There is also the viewpoint that both World War I and World War II are part of the same "European Civil War" or "Second Thirty Years War": ; .〕 The British historian Antony Beevor views the beginning of the Second World War 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 (2 September 1945). A peace treaty with Japan was signed in 1951 to formally tie up any loose ends such as compensation to be paid to Allied prisoners of war who had been victims of atrocities.〔.〕 A treaty regarding Germany's future allowed the reunification of East and West Germany to take place in 1990 and resolved other post-World War II issues.〔(【引用サイトリンク】url=http://usa.usembassy.de/etexts/2plusfour8994e.htm )〕
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