In 1904, Shimada joined the navy General Staff and became an instructor at the Naval War College. Promoted to captain in 1928, he commanded first the cruiser Tama and then the battleship Hiei (1928). Following promotion to rear admiral in 1929, Shimada became chief of staff of the Second Fleet and then chief of staff of the Grand Fleet in 1930. In 1931, he became the director of the Submarine School, and in 1932, he was chief of staff of the Third Fleet. He next held various posts on the navy General Staff. Promoted to vice admiral in 1934, Shimada became the deputy chief of the Naval Staff until he was assigned as commander of the Second Fleet in 1937. Promoted to admiral in 1940, Shimada became the commander in chief of the China Fleet, and later he served as the commander in chief of the Kure and Yokosuka Naval Districts.
In October 1941, Shimada became minister of the navy in the cabinet of Prime Minister Tojo Hideki, who had rejected the first candidate, Admiral Toyoda Soemu, who was known to be "anti-army." Shimada owed his appointment to his ability to get along with those around him. Although he shared the navy's reluctance to go to war against the United States, he found that it was impossible to swim against the tide and followed Tojo's policies. In February 1944, Shimada assumed the office of chief of the navy General Staff, tasked with Tojo's demand to conduct the war at sea more effectively. From that date, Shimada concurrently held the offices of minister of the navy and chief of the navy General Staff. Navy and intellectual circles denigrated him, whispering that "Shimada is Tojo's puppet." Following the loss of Saipan, in July 1944 Tojo reluctantly ordered Shimada to resign before resigning himself.
In January 1945, Shimada went on the reserve list. After the war, Shimada was arrested by Allied authorities as a Class A war criminal. Tried and convicted by the International Military Tribunal for the Far East, he was sentenced to life in prison, but he was released in 1956. Shimada died in Tokyo on 7 June 1976. Asakawa Michio
Evans, David C., and Mark R. Peattie. Kaigun: Strategy, Tactics and Technology in the Imperial Japanese Navy, 1936–1941. Annapolis, MD: Naval Institute Press, 1997.