The US government decided to cut off US oil exports and since the Japanese relied on the United States for eighty percent of its oil, and without US oil supplies its navy wouldn't be able to function. Therefore, attacking Pearl Harbor the Japanese hoped to cripple or destroy the US Pacific fleet so the Japanese navy would have free reign of the Pacific
"Yesteryday, December 7, 1941- a date which will live in infamy- the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan"
On the morning of December 7, 1941. Japan attacked the US naval base at Pearl Harbor, Hawaii.
The surprise attack by approximately 350 Japanese aircraft sunk or were damaged, including eight battleships; destroyed or damaged 300 US aircraft and 2,403 men killed
Roosevelt addressed a joint session of Congress in the Capitol
Roosevelt then asked Congress to declare war against Japan
Three days later, Japan's allies Germany and Italy declared war on the United States, and Congress reciprocated the same day.