Japan attacked Pearl Harbour to stop the US fleet interfering with its conquests, but it brought the USA fully into the war.
Pearl Harbour was a US naval base in Hawaii, in the Pacific Ocean. It held the Pacific Fleet, a large force of American warships. Japanese leaders expected this fleet could interfere with their planned advance into Southeast Asia. On 7 December 1941, Hawaii time, Japan attacked the base by surprise. It aimed to damage the fleet and gain time to seize territory and organise its defence.
Japan attacked other places in the region as part of the same offensive. In Malaya and elsewhere in Asia, these attacks are dated 8 December, because local time was ahead of Hawaii across the International Date Line. In fact, landings at Kota Bharu in Malaya began before Pearl Harbour, even though the local date was 8 December.
The attack caused severe losses. But the US aircraft carriers, ships that carry and launch planes, were not in the harbour. And the USA's huge factories could replace lost ships and planes. On 8 December, President Franklin Roosevelt spoke to Congress, the US law-making body, which declared war on Japan.
So Japan gained surprise and damaged many ships. But instead of removing the USA's ability to fight, it brought a powerful enemy into a long war.
- 7 December 1941
- Surprise attack on Pearl Harbour, Hawaii time.
- Kota Bharu
- Landings in Malaya began before Pearl Harbour.
- 8 December 1941
- US Congress declares war on Japan.
Worked example: Aim versus result
Japan wanted to stop US interference while it advanced south.
- Aim: damage the fleet to gain time.
- Limit: the carriers were away, and US factories could build more.
- Result: the USA entered the war fully, as a powerful enemy.
Watch out for this
The USA declared war on Japan before Pearl Harbour.
The USA declared war on 8 December 1941, the day after the attack.
Check your understanding
Why did Pearl Harbour not knock the USA out of the war?
- Japan did not damage any ships.
- Its carriers were away, and its factories could replace losses.
- The USA was already at war with Japan.