Yamamoto Isoroku, (1884–1943), the Japanese admiral who led the attack on Pearl Harbor, Hawaii, December 7, 1941, starting war with the United States. Yamamoto served in the Russo-Japanese War, 1904–05, and became vice minister of the navy in 1936 and chief of its aviation department in 1938. As commander in chief of the combined fleet he planned and directed the attack on Pearl Harbor. He was killed in an air action in the southwest Pacific. The Americans, having broken the Japanese code, knew his flight plan and intercepted and shot down the plane in which he was flying.