World War II, or the Second World War was a global military conflict lasting from 1939 to 1945, which involved most 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 military personnel mobilised. In a state of “total war,” the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources.