The Imperial Japanese Navy struck Pearl Harbor on December 7, 1941, but none of the Pacific Fleet's aircraft carriers were in the harbor. Because a large fraction of the navy's battleship fleet was put out of commission by the attack, the undamaged aircraft carriers were forced to become the load-bearers of the early part of the war. The first aircraft carrier offensive of the U.S. Navy came on February 1, 1942, when the carriers Enterprise and Yorktown, attacked the Japanese bases in the Marshall and Gilbert Islands. The Battle of the Coral Sea became the first sea battle in history in which neither opposing fleet saw the other. The Battle of Midway started as a Japanese offensive on Midway Atoll met by an outnumbered U.S. carrier force, and resulted in a U.S. victory. The Battle of Midway was the turning point in the Pacific War.