Attack on Pearl Harbor

On the morning of 7 December 1941, carrier-based aircraft of the Empire of Japan struck the US Pacific Fleet at its base at Pearl Harbor, on the Hawaiian island of Oahu. The United States was not yet at war, and the surprise raid killed more than 2,400 Americans. Within days the attack had drawn the United States fully into World War II, in both the Pacific and Europe.

Relations between Japan and the United States worsened through the 1930s as Japan expanded on the Asian mainland, first in Manchuria from 1931 and then in the Second Sino-Japanese War from 1937. When Japan moved into French Indochina in 1940, Washington cut off sales of aircraft, machine tools and aviation fuel, and President Franklin D. Roosevelt, hoping to deter Japan, had already moved the fleet's base from San Diego to Hawaii in mid-1940. In July 1941 the United States stopped oil exports, on which Japan depended heavily. Japan then prepared to seize the oil of the Dutch East Indies while negotiations dragged on.

Admiral Isoroku Yamamoto, commander of the Combined Fleet, designed the raid as a pre-emptive blow to keep the American fleet from interfering with Japanese conquests in Southeast Asia, hoping that early gains would allow a negotiated peace.

The strike force under Chūichi Nagumo, built around six aircraft carriers, sailed from the Kuril Islands on 26 November 1941. An army radar station at Opana Point detected the incoming aircraft, but the contact was mistaken for American bombers expected from the mainland. The attack began at 7:48 am local time. In two waves, 353 Japanese fighters, dive bombers, level bombers and torpedo bombers hit the battleships moored in the harbour and the surrounding airfields.

All eight US battleships present were damaged and four were sunk. The USS Arizona blew up when her forward magazine exploded, killing 1,177 men, nearly half of all American deaths that day. In total 2,403 Americans died and 1,178 were wounded, and more than 180 aircraft were destroyed. Japan lost 29 aircraft, five midget submarines and about 130 men.

Japan had intended to break off talks shortly before the attack, but its message to Washington, which in any case did not formally declare war, was delivered more than an hour after the bombs began to fall. Over the same few hours, Japan also attacked the Philippines, Guam, Wake Island, Malaya, Singapore and Hong Kong.

The raid missed its most valuable targets. The fleet's three aircraft carriers were at sea, and the Japanese left the oil storage tanks, repair yards and submarine base untouched. Apart from the Arizona and the old target ship Utah, every sunk vessel was refloated, and six of the eight battleships fought again later in the war. The intact base went on to support American operations such as the Battle of Midway in June 1942. A Japanese admiral, Chūichi Hara, later summed up the outcome as a great tactical victory that cost Japan the war.

On 8 December Roosevelt asked Congress for a declaration of war, calling 7 December "a date which will live in infamy"; Congress agreed within the hour. Britain declared war on Japan the same day. On 11 December Germany and Italy followed with their own declarations of war against the United States, though their pact with Japan did not oblige them to.

The attack also led to the forced removal of more than 110,000 Japanese Americans, almost all from the West Coast, to inland camps. In Hawaii itself, where people of Japanese descent made up over a third of the population, between 1,200 and 1,800 people were held.

Our 1938 map shows the Empire of Japan and the United States before the war, and the 1945 map shows the Pacific at its end.