1939–1945 global war between the Axis and the Allies
World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from more than 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 70 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. Tens of millions of people died during the conflict due to genocides, premeditated death from starvation, massacres, and disease. Aircraft played a major role in the conflict which included the use of terror bombing, strategic bombing and the only use of nuclear weapons in war.
World War II on wikipedia