he joined Admiral Isoroku Yamamoto in vocal opposition to the terms of the disarmament treaty. After his return to Japan, he was assigned as executive officer on the cruiser from July 1930. From November 1930, he was assigned to the staff of the Combined Fleet. He served as an instructor at the Naval Staff College from November 1932 and was promoted to the rank of captain in December of that year. Yamaguchi was the naval attaché to the Japanese embassy at Washington, D.C., from June 1934 to November 1936. On his return to Japan, he received his first command, the cruiser from December 1936 to December 1937, followed by the battleship to December 1938. World War II With the start of the Second Sino-Japanese War, Ise was assigned to patrols off the southern Chinese coast. Yamaguchi was promoted to rear admiral on 15 November 1938. From December, he was the chief-of-staff of the IJN 5th Fleet and from November 1939 was on the staff of the IJN 1st Fleet. in January 1940, he became commander of the 1st Combined Air Group, and in this capacity directed a saturation bombing campaign in central China through 1940, including the Bombing of Chongqing. In November 1940, Yamaguchi was reassigned to command the 2nd Carrier Division, consisting of the aircraft carriers and . In preparation for the attack on Pearl Harbor, Yamaguchi trained his flight crews ruthlessly, which led to many accidents and complaints; however, the training paid off after the start of combat operations. Following the successful strike against the American fleet at Pearl Harbor, Yamaguchi′s carrier force participated in the Battle of Wake Island. After the start of 1942, he was sent south to assist in the Battle of Ambon in the Dutch East Indies, followed by the Bombing of Darwin in February. In March, his carriers supported Japanese forces in the Battle of Java, sweeping the Dutch East Indies of remaining Allied warships. In April, he crossed into the Indian Ocean to support the large-scale raid against the Royal Navy at and near Ceylon. Yamaguchi returned to Japan briefly in late April for maintenance on his fleet. In June 1942, he was assigned to the Midway operation. During the battle, on 4 June 1942, Yamaguchi disagreed with the fleet commander, Vice Admiral Chūichi Nagumo. A reconnaissance plane discovered an American aircraft carrier () near Midway. At that moment, the Japanese planes