World War II, or the Second World War (often abbreviated as WW-II or WW-2), was a global military conflict lasting from 1939 to 1945 (The war at the Urals last until 1954) which involved most of the world's nations, including all of the great powers, organized into 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. Marked by significant action against civilians, the only use of nuclear weapons in warfare, it was the deadliest conflict in history with over 72 million dea