Pearl Harbor is a naval base in the U.S. state of Hawaii, on the island of Oahu. Using this base, the U.S was able to have a good position on the advancing Japanese fleet. However, the Japanese bombed Pearl Harbor, on December 7, 1941, which was a surprise. The attack led to America's fighting in World War II.
Admiral Yamamoto led a surprise attack on Pearl Harbor on December 7, 1941. The reason the Japanese attacked Pearl Harbor was to destroy the U.S. Navy (Seventh Fleet), and prevent the U.S from stopping the Japanese expansion in Asia.