World War II was a conflict that involved virtually every part of the world during the years 1939–45.
The principal belligerents were the Axis powers—Germany, Italy, and Japan—and the Allies—France, Great Britain, the United States, the Soviet Union, and, to a lesser extent, China.
The war was in many respects a continuation, after an uneasy 20-year hiatus, of the disputes left unsettled by World War I.
The 40,000,000–50,000,000 deaths incurred in World War II make it the bloodiest conflict, as well as the largest war, in history.
On August 15, 1945, Japan formally surrendered. World War II was over. A new age of nuclear weapons had begun, and a cold war between the two superpowers that emerged from the war—the United States and the Soviet Union—would result in many “surrogate wars” in the decades to come, wars fought in and between nations backed by one side or the other.