Ships
- IJN Hosho Captain from 15 November 1934 · Relieved on 12 June 1935
Seigo Yamagata was born in Yamaguchi Prefecture on 15 February 1891 and entered the Imperial Japanese Navy through the Naval Academy at Etajima. He graduated in July 1911, fifth in the 39th class, and after the midshipman cruise joined the fleet the following spring. His early sea duty ran through cruisers, the battleship Fuso, and destroyers, and most of it was torpedo work. That leaning stayed with him. Long after he had moved into aviation, he still rated bombers and torpedo planes above fighters.
He set out to master the specialty rather than chase a staff career. Promoted lieutenant in December 1917, he passed through the Naval War College's shorter course and the advanced course at the Torpedo School, then served as a division officer, as torpedo officer of the destroyer Yakaze, and as captain of the destroyer Ariake. In December 1922 he returned to the Naval War College for the A course. After graduation he was torpedo officer of the battleship Yamashiro and worked in the ordnance shops at Yokosuka and on the administrative staff of the Sasebo yard, close to the design and manufacture of torpedoes. From the autumn of 1927 he spent about a year and a half in Britain as an ordnance inspector, adding mines, depth charges, and minesweeping to what he already knew. He was promoted commander in December 1928.
The move into aviation came in 1932, as he was about to make captain. Ordered to the Navy's aeronautical headquarters, he joined its administrative staff. The shift was an odd one for a torpedo specialist, but the headquarters was then led by Shigeru Matsuyama, another torpedo man, who was pushing the Navy toward aerial torpedo attack. Yamagata took up the work on air-launched torpedoes and on the aircraft meant to carry them. Out of that effort came the Type 96 land-attack plane, which later flew the long over-water bombing raids of the China war. He was promoted captain on 1 December 1932 and, from April 1933, headed a section in the same headquarters.
On 15 November 1934 the regular officer rotation gave him his first ship, and the only one he would ever command: the aircraft carrier Hosho. He relieved Rokukichi Takeda. Hosho, completed in 1922, was Japan's first purpose-built carrier and had already been in the Shanghai fighting of 1932. By the middle of the 1930s she was a small ship, used mainly to train aviators. The months of his command were quiet. Relations with China were stalled, and the carrier's one notable voyage was a cruise toward Shanghai to show the flag. He left her on 12 June 1935.
He went next to the Air Arsenal and on 31 October 1935 became chief of its administrative bureau. In December 1936 the Naval College appointed him an aviation instructor. There he argued that aircraft should carry the main weight of a fleet battle: fold air power into the plan for wearing down an advancing enemy, ease the battleship program, enlarge the shore-based air groups, and provide tenders for flying boats. He continued to put large land-based bombers and torpedo planes ahead of carrier fighters, and pilots in the carrier-fighter community resented the slight. When the Army, looking at the new German air force, proposed an independent Japanese air service, he answered as a Navy man. He granted what aircraft could do, and he held that an air arm cut loose from the fleet would leave the Navy without a role. He also set a condition the Army did not want. Crews of any such service would have to learn to navigate and strike far out at sea, over empty water. His stand helped bring the proposal to an end.
Promoted rear admiral in 1938, he took command of the 3rd Combined Air Group, a south China force built around carrier-type aircraft and based ashore. He directed its bombing and reconnaissance through the operations that included the landings on Hainan in 1939. In November 1939 he received the Order of the Sacred Treasure, Second Class. Late in 1940 he returned to aeronautical headquarters as chief of administration, overseeing the organization of air groups and the development of new aircraft into the first months of 1942. He was still there when the Pacific War began. In April 1942 he was given the 26th Air Flotilla at Rabaul, his last command of a flying force. Based there, the flotilla fought in the South Pacific air war. Promotion to vice admiral followed on 1 May 1942. In June 1943, with the air-fleet commands suited to a vice admiral already filled, the Navy sent him to the Takao Guard District on Taiwan, well behind the fighting.
The quiet posting did not hold. In November 1943 he was ordered to the new 4th Southern Expeditionary Fleet, responsible for the eastern Netherlands East Indies, as General Douglas MacArthur prepared to come back across the Southwest Pacific. A classmate, Yoshikazu Endo, took the 9th Fleet in western New Guinea and was killed when that force was destroyed in May 1944. MacArthur then left the eastern Indies aside and went for the Philippines. The fleet Yamagata had been sent to command spent the rest of its existence off the main line of the offensive, and in March 1945 it was ordered dissolved.
He boarded a flying boat bound for the home islands. The aircraft came down on the coast of China, outside Japanese control. On 17 March 1945, faced with capture, he took his own life. He was fifty-four. Imperial General Headquarters counted him killed in action and promoted him posthumously to admiral.