Japan felt the need to gain land from other countries to get materials and supplies, they did this mainly through force.
Effect On Hawaii
The U.S. Froze Japans assets because they were worried about their intentions. This took away about 90% of raw materials needed for the war production of Japan.
FDR/ "Date that will live in infamy"
Yesterday, December 7th, 1941 -- a date which live in infamy
The attack happened on December 7th, 1941; it was an early Sunday morning. The U.S. was not prepared at all and Japan ended up destroying the U.S. Pacific Fleet Battleship Force.
Effect on People of Japanese Descent in America
All airports in Hawaii were taken over by the U.S. Army and Hawaii went into a state of Martial Law. Private Planes were grounded.
FDR said that Pearl Harbor will always be a day that will be given bad reputation. He asked Congress to declare war and in the speech it shows why: Japan had given no warning of the attack and it has obviously been planned.