 Mutsu's anti-aircraft armament was upgraded during 1932. Upon completion, she was assigned to Battleship Division 1 of the 1st Fleet, and again served as the Emperor's flagship during the annual maneuvers and fleet review in 1933. The ship was placed in reserve on 15 November and began her lengthy reconstruction. This was completed on 30 September 1936 and Mutsu rejoined the 1st Battleship Division on 1 December 1936. In August 1937, she transported 2,000 men of the 11th Infantry Division to Shanghai during the Second Sino-Japanese War. Her floatplanes bombed targets in Shanghai on 24 August before she returned to Sasebo the following day. On 15 November 1938, Captain Aritomo Gotō assumed command of the ship. Mutsu was placed in reserve from 15 December 1938 to 15 November 1939. She was refitted in early 1941 in preparation for war; as part of this work, she was fitted with external degaussing coils and additional armor for her barbettes.
