The major global conflict initiated by the surprise attack by Japan on Pearl Harbor is World War II. The attack occurred on December 7, 1941, when Japanese forces launched a sudden offensive on the U.S. naval base in Hawaii, leading to significant damage to the Pacific Fleet, including the sinking of battleships and destruction of aircraft. This attack galvanized the American public and led to the United States' formal entry into the war against the Axis powers. The subsequent mobilization of American forces contributed to crucial victories in both the Pacific and European theaters, ultimately turning the tide against Axis aggression.