High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! World War II, or the Second World War was a global military conflict between 1939 and 1945, which involved most of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis. The war involved the mobilization of over 100 million military personnel, making it the most widespread war in history. 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.