World War II was a global military conflict that, in terms of lives lost and material destruction, was the most devastating war in human history. It began in 1939 as a European conflict between Germany and an Anglo-French coalition but eventually widened to include most of the nations of the world. It ended in 1945, leaving a new world order dominated by the United States and the USSR.
More than any previous war, World War II involved the commitment of nations' entire human and economic resources, the blurring of the distinction between combatant and noncombatant, and the expansion of the battlefield to include all of the enemy's territory. The most important determinants of its outcome were industrial capacity and personnel. In the last stages of the war, two radically new weapons were introduced: the long-range rocket and the atomic bomb. In the main, however, the war was fought with the same or improved weapons of the types used in World War I. The greatest advances were in aircraft and tanks.