generally considered to have lasted from 1939 to 1945, although some conflicts in
Asia that are commonly viewed as becoming part of the world war had been going on
earlier than that. 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, with more than 100 million people, from
more than 30 different countries, serving in military units. 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 and the only use of
nuclear weapons in warfare, 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 East Asia 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 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 formed the Axis alliance with Italy,
conquering or subduing much of continental Europe. Following the Molotov–
Ribbentrop Pact, Germany and the Soviet Union partitioned and annexed territories
between themselves of their European neighbours, including Poland and the Baltic
states. The United Kingdom and the other members of the British Commonwealth were
the only major Allied forces continuing the fight against the Axis, with battles taking
place in North Africa as well as the long-running Battle of the Atlantic. In June 1941,
the European Axis launched an invasion of the Soviet Union, giving a start to the
largest land theatre of war in history, which tied down the major part of the Axis' military
forces for the rest of the war. In December 1941, Japan joined the Axis, attacked the
United States and European territories in the Pacific Ocean, and quickly conquered
much of the Western Pacific.
The Axis advance was stopped in 1942. Japan lost a critical battle at Midway, near
Hawaii, and never regained its earlier momentum. Germany was defeated in North
Africa and, decisively, at Stalingrad in Russia. In 1943, with a series of German
defeats in Eastern Europe, the Allied invasion of Italy which brought about that nation's
surrender, and American victories in the Pacific, the Axis lost the initiative and
undertook strategic retreat on all fronts. In 1944, the Western Allies invaded France,
while the Soviet Union regained all of its territorial losses and invaded Germany and its
allies. During 1944 and 1945 the United States defeated 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, 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 (known as Operation Downfall)
imminent, and the Soviet Union having declared war on Japan by invading Manchuria,
Japan surrendered on 15 August 1945, ending the war in Asia and cementing the total
victory of the Allies over the Axis.
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 great powers that were the victors of the war—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 started to
decline, 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 stabilise postwar relations and cooperate
more effectively in the Cold War.[citation nee