Final answer:
On December 7, 1941, the U.S. naval base at Pearl Harbor was attacked by Japan, leading to the United States' entry into World War II.
Step-by-step explanation:
On December 7, 1941, the Japanese attacked the U.S. naval base at Pearl Harbor, located in Hawaii. This event brought the United States into World War II. The surprise attack resulted in significant damage to the U.S. Pacific Fleet and led to the formal declaration of war by the United States on Japan the following day. The attack on Pearl Harbor is often considered a turning point in American history and marked the beginning of the U.S. involvement in the war.
Learn more about Pearl Harbor attack