Answer: Oil.
Japan wanted southern Indochina's supply of oil as they were starved for it and unable to maintain their military. On the same day they attacked Pearl Harbour they also attacked the Philippines to gain access to this oil. The attack on Pearl Harbour was to prevent any armada of US ships from retaking the Philippines, which they succeeded at doing.
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John Steinbeck's the Pearl takes place in La Paz, Mexico.
Steinbeck was inspired to write the story after hearing a folk talk while visiting Baja (where La Paz is located) which is a heavy pearl producing region.
I believe the answer is the great depression and the president at the time was Franklin Roosevelt
The US economy was in a depression