The Japanese attack fleet of 33 warships and auxiliary craft, including six aircraft carriers, sailed from northern Japan for the Hawaiian Islands.
The attack on Pearl Harbor was the culmination of a decade of deteriorating relations between Japan and the United States over the status of China and the security of Southeast Asia. The breakdown began in 1931 when Japanese army extremists, in defiance of government policy, invaded and overran the northern-most Chinese province of Manchuria. Japan ignored American protests, and launched a full-scale attack on the rest of China in the summer of 1937. Although alarmed by this action, neither the United States, nor any other nation with interests in the Far East, was willing to use military force to halt Japanese expansion.
Over the next three years, war broke out in Europe, and Japan joined Nazi Germany in the Axis Alliance. The United States applied both diplomatic and economic pressures to try to resolve the Sino-Japanese conflict. The Japanese government viewed these measures, especially an embargo on oil, as threats to their nation's security. By the summer of 1941, both countries had taken positions from which they could not retreat without a serious loss of national prestige. Although both governments continued to negotiate their differences, Japan had already decided on war.
The attack on Pearl Harbor was part of a grand strategy of conquest in the Western Pacific. The objective was to immobilize the Pacific Fleet so that the United States could not interfere with these invasion plans. The principal architect of the attack was Admiral Isoroku Yamamoto, Commander-in-Chief of the Japanese Combined Fleet. Though personally opposed to war with America, Admiral Yamamoto knew that Japan's only hope of success in such a war was to achieve quick and decisive victory. America's superior economic and industrial might would tip the scales in her favor during a prolonged conflict.
On November 26, the Japanese attack fleet of 33 warships and auxiliary craft, including six aircraft carriers, sailed from northern Japan for the Hawaiian Islands. The fleet followed a route that took it far to the north of the normal shipping lanes. By early morning, December 7, 1941, the ships had reached their launch position, 230 miles north of Oahu. At 6:00 a.m., the first wave of fighters, bombers, and torpedo planes took off. The night before, some 10 miles outside the entrance to Pearl Harbor, five midget submarines carrying two crewmen and two torpedoes each were launched from larger "mother" subs. Their mission: enter Pearl Harbor before the air strike, remain submerged until the attack got underway, then cause as much damage as possible.
Meanwhile, at Pearl Harbor, the 130 vessels of the U.S. Pacific Fleet lay calm and serene. Seven of the fleet's nine battleships were tied up along "Battleship Row" on the southeast shore of Ford Island. Naval aircraft were lined up at Ford Island and Kaneohe Bay Naval Air Stations, and at Ewa Marine Corps Air Station. The aircraft belonging to the U.S. Army Air Corps were parked in groups as defense against possible saboteurs at Hickam, Wheeler, and Bellows airfields.
While the attack on Pearl Harbor intensified, other military installations on Oahu were hit. Hickam, Wheeler, and Bellows airfields, Ewa Marine Corps Air Station, Kaneohe Bay Naval Air Station, and Schofield Barracks suffered varying degrees of damage, with hundreds of planes destroyed on the ground and hundreds of men killed or wounded.
At 6:40 am, the crew of the destroyer USS Ward spotted the conning tower of one of the midget subs headed for the entrance to Pearl Harbor. The Ward sank the sub with depth charges and gunfire, then radioed the information to headquarters.