What Caused America's Entry Into World War II?

Prior to Pearl Harbor, Japan had been expanding its territories in the Pacific and feared the United States would interfere. On top of the existing oil embargo against Japan, the presence of the U.S. Navy in the Pacific would have crippled Japan's ability to procure natural resources such as oil, rubber and tin. Therefore, Japan sent a force of dive bombers, fighters and aircraft carriers as well as submarines to attack the naval base early in the morning. The United States lost eight battleships, more than 150 fighter planes and more than 2,000 military personnel. However, the American aircraft carriers were untouched, enabling a quick rebuilding of the forces.