Who was the leader of the U.S. during WW2?

The leader of the United States during World War II was President Franklin D. Roosevelt. He served from March 4, 1933, until his death on April 12, 1945. Roosevelt played a crucial role in mobilizing the U.S. economy for war and establishing international alliances, such as with the United Kingdom and the Soviet Union, to combat the Axis powers. His leadership was pivotal in shaping U.S. involvement in the conflict.