Before Sept. 11, 2001, the United States mainland had never been attacked by any foreign power. The closest to this was the bombing of the US naval base at Pearl Harbor in Hawaii on Dec. 7, 1941 by fighter planes of the Japanese imperial navy. The attack led the United States directly into the Pacific and European theaters of World War II. America declared war on Japan the following day, putting to a close the domestic debate on the wisdom of openly opposing Japanese and German aggression. Three days later, for its support of Britain, Germany and Italy declared war against the United States.