World War II
- World War II 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.
- World War II 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.
- 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.
- 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.
- The Main Allied leaders were Joseph Stalin (Soviet Union), Franklin D. Roosevelt (United States), Winston Churchill (United Kingdom) and Chiang Kai-shek (Republic of China). The Main Axis leaders were Adolf Hitler (Nazi Germany), Hirohito (Empire of Japan) and Benito Mussolini (Kingdom of Italy)
- 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
- 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.