World War II (WWII or WW2), also known as the Second World War, was a global war. It lasted from 1938 to 1946, though some related conflicts in Asia began before 1938. 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 more than 30 different 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, the Three Alls Policy, the strategic bombing of enemy industrial a