When did WWII start?

The start of World War II is generally considered to be September 1, 1939, when Nazi Germany invaded Poland. This led to declarations of war on Germany by several countries, including the United Kingdom and France. The war lasted six years and involved the majority of the world’s nations, including all of the great powers, eventually forming two opposing military alliances: the Allies and the Axis. The war ended on September 2, 1945, with the official surrender of Japan, after the atomic bombings of Hiroshima and Nagasaki by the United States.