The major conflict fought between 1939 and 1945, involving most of the world’s nations, was World War II. This global war was primarily triggered by aggressive expansionist policies from dictatorial regimes, notably Nazi Germany under Adolf Hitler. It involved multiple theaters, including Europe, North Africa, and the Pacific, and saw significant battles such as Stalingrad, Normandy, and Midway. The war resulted in monumental loss of life, the Holocaust, and extensive destruction. It ultimately ended with the unconditional surrender of Axis powers in 1945. The aftermath reshaped international relations, led to the establishment of the United Nations, and laid the groundwork for the Cold War.