The Japanese aerial attack on US shipping at Pearl Harbor on the island of Oahu, Hawaii, was launched at 7.55am on Sunday 7 December. Devastatingly efficient, and apparently unexpected, it was characterized by President Roosevelt as “the day that will live in infamy” and precipitated the US declaration of war on Japan.
The attack was a preemptive strike, aimed at disabling the US Pacific Fleet, thereby weakening any resistance to Japanese territorial expansion. It was also a reaction to the deterioration in US-Japanese relations, a result of Japan’s aggressive campaign of conquest and exploitation in Southeast Asia. In January 1940 the US had allowed a long-standing commercial treaty with Japan to lapse, going on in the summer to embargo trade in scrap iron and aviation fuel. Japan was dependent on the US for both natural and industrial resources and was becoming increasingly alarmed. When Japan signed the Tripartite Pact with Germany and Italy, making it a formal member of the Axis, the US – officially neutral, but supportive of Britain – brought in further embargoes.
When six Japanese aircraft carriers left Japan for Hawaii on 26 November 1941, laden with over 400 aircraft that would attack the naval base at Pearl Harbor in two waves, the US was staggeringly unprepared. Although US intelligence was able to decode Japanese communications, their findings were not adequately communicated and even when radar spotted incoming planes, they were discounted as a flight of B-17 bombers.
The first wave of Japanese aircraft set about bombing US airfields and aircraft to cripple any defensive aerial threat. Heavy bombs and torpedoes were also dropped over the naval base, immediately causing heavy damage to the unsuspecting ships. The second wave of the Japanese attack began at around 08:50 and was met with a much more coordinated defensive response, but ultimately many American vessels were destroyed.
Following the two attack waves, all of the US battleships in port were destroyed or heavily damaged, although five were refloated and eventually returned to service after being repaired, an outcome which probably would not have been possible had the ships been attacked in deeper waters. Despite temporarily crippling the US Pacific Fleet and inflicting over 2,400 deaths, the Japanese attack crucially spared the US Pacific Fleet’s three aircraft carriers, which were already deployed elsewhere.
The attack on Pearl Harbor had the effect of galvanizing the American people and uniting them behind President Roosevelt and the war. Polls show that his declaration of war on Japan, which was made the day after the attack, was met with approval by 97 percent of the American public. US industrial and military capacity was mobilized, weapons and supplies were sent to Britain and Russia, Japanese-Americans were sent to internment camps. The ‘sleeping giant’ had awoken.