Early on the morning of Sunday, December 7, 1941—a day that President Franklin D. Roosevelt proclaimed would "live in infamy"—Japanese fighter pilots attacked the U.S. naval base at Pearl Harbor, Hawaii. This surprise attack, which Japan undertook without a declaration of war, provoked the United States to end its neutral stance on World War II and join the Allies (Great Britain, France, and the Soviet Union).
In early 1941, the Japanese government began a two-pronged strategy. Japanese diplomats in Washington, D.C. entered into negotiations regarding Japan's desire for expansion in Asia; at the same time, the Japanese Navy was directed to develop plans for an attack on the United States should the negotiations fail (which they did). Under the direction of Adm. Isoroku Yamamoto, the Japanese outlined an attack on Pearl Harbor that would disable the U.S. fleet while Japanese forces simultaneously launched invasions into Southeast Asia and the Pacific islands.
At dawn on December 7, a Japanese task force was positioned 275 miles north of Hawaii. The first wave of 51 dive bombers, 40 torpedo bombers, and 43 escorting fighters took off without incident. As they approached Hawaii, they were detected on U.S. radar screens, but because the technology was new and the technicians poorly trained, the technicians were unable to read the size of the approaching force. They assumed it was a flight of B-17 bombers arriving from the U.S. mainland. Thus, the Japanese were able to launch their attack with no warning given at the target. Just before 8:00 A.M., when flight leader Mitsuo Fuchida saw the U.S. ships completely open to attack, he signaled the code words for success: "tora [tiger], tora, tora."
Not until the bombs began to fall did the Americans respond. As "battle stations" sounded on the parked ships, the sailors operated whatever guns they could reach. There was little they could do as the attacking aircraft scored hits immediately. Four of the docked battleships were hit by torpedoes in the first five minutes as the dive bombers and fighters attacked from above. Japanese fighter aircraft strafed U.S. aircraft parked at the half-dozen airfields on the island of Oahu. Only 38 U.S. aircraft were able to get airborne and engage the attackers, and 10 of those were shot down.
The first attack went on for 25 minutes and then was followed by a second wave at 8:45 A.M. The second wave was less successful, suffered more casualties, and did little more than add finishing touches to the already battered U.S. ships. In all, the Japanese lost only 29 planes and 55 aircrew; they had expected to lose half their force. It was as complete a surprise attack as possible.
The outrage of Americans was palpable after the attack. Pearl Harbor was the worst naval disaster in U.S. history, with more than 2,000 casualties, dozens of aircraft destroyed, and 21 ships damaged or destroyed. (Three battleships, three destroyers, and three cruisers were disabled, and five battleships—including the Oklahoma and the Arizona—were sunk or destroyed). The U.S. Congress declared war on Japan on December 8, 1941. Japan's allies, Germany and Italy, declared war on the United States on December 11.