This paper discusses why the U.S. and Japan went to war in 1941. The paper finds that Japanese nationalism and militarism threatened American security. The Japanese hoped to conquer new territories so that they could get new markets for Japanese goods and provide raw materials for Japanese industries. The U.S. was threatened by the Japanese aggression and imposed an embargo on Japan. The Japanese ended up attacking Pearl Harbor because the U.S. represented the biggest stumbling block to Japanese expansion in the Pacific. 5 pgs. Bibliography lists 3 sources.