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.
World War II was a conflict that involved virtually every part of the world during 1939–45. The main combatants were the Axis powers (Germany, Italy, and Japan) and the Allies (France, Great Britain, the United States, the Soviet Union, and China).