When the Japanese attacked Pearl Harbour that forced the Americans into World War II on the side of the Allies. Roosevelt called December 7 "a date that will live in infamy". In a little more than two hours, the Japanese had sunken 21 ships and killed more than 2000 americans. However the three targeted American aircraft carriers were not in port. As the Americans later proved the American aircraft carriers were the dominant ship in the American fleet. By not sinking their aircraft carriers, the Jpanese had left the American navel force mainly intact. When Roosevelt talked to congress to declare war on the Empire of Japan the answer was a resounding yes. Soon after that America declared war on Germany and italy as well. America was greatly divided over how much help to give the Allies. Now they had a common purpose "make the Japanese pay for Pearl Harbour."
Admiral Isoruku Yamamoto, who had planned the Japanese attack on Pearl harbour had studied at Harvard university and knew full well the capabilities of the American people. He had warned others in the Japanese government that for the Pearl Harbour attack to succeed, it must be a crushing blow. The attack was devastating, but it wasnt a crushing blow. Then on december 8th 1941, the Empire of Japan declared war on United states and Britain.