Japan aimed to damage the American fleet long enough to secure its southern conquests. It damaged the fleet, but also brought the United States fully into the war.
Pearl Harbour was an American naval base in Hawaii, in the Pacific Ocean. The Pacific Fleet was a major force of American warships. Japanese leaders expected it could interfere with their planned advances into Southeast Asia. They attacked the base by surprise on 7 December 1941, Hawaiian time, aiming to damage the fleet and gain time to seize territory and organise its defence.
Japan also launched attacks and landings elsewhere in the region as part of the same offensive. Operations in Malaya and other parts of Asia were dated 8 December because local time was ahead of Hawaii, across the International Date Line. For example, landings at Kota Bharu in Malaya began before Pearl Harbour, although the local date was 8 December.
The attack caused severe losses, but American aircraft carriers, ships that carry and launch aircraft, were not in the harbour. The United States could also draw on its large industrial base to replace losses. On 8 December, President Franklin Roosevelt addressed Congress, the American legislature, which declared war on Japan. Japan had gained surprise and damaged ships, but had brought a powerful opponent into a long conflict rather than removed its ability to fight.
Worked example: Compare the intended advantage with the result
Japan wanted to reduce American interference while it advanced south.
- Damaging the fleet could delay American naval operations and give Japan more time to secure its gains.
- But damaging ships at one base did not destroy absent carriers or the factories able to build more ships and aircraft.
- The American declaration of war showed commitment to fight. Immediate damage did not mean the long-term opponent had been removed.
Watch out for this
The United States declared war on Japan before the Pearl Harbour attack.
The attack was on 7 December Hawaiian time; the American declaration followed on 8 December.
Check your understanding
Which explanation best connects Pearl Harbour to Japan's wider plans?
- The naval damage proves that the attack removed America's capacity to fight a long war.
- The absence of American carriers means that interfering with the Pacific Fleet could not have been Japan's aim.
- Japan sought time for its southern conquests by damaging a naval force that might interfere.