Ships
- IJN Yamagumo Captain from 15 November 1939
Yasuji Koga, an officer of the Imperial Japanese Navy, became captain of the destroyer Yamagumo on 15 November 1939. His previous command had been the destroyer Minazuki. Yamagumo, an Asashio-class ship built by Fujinagata in Osaka, had been launched in July 1937 and commissioned on 15 January 1938. He joined her as a lieutenant commander.
On the day he took command, Yamagumo entered the 9th Destroyer Division with Asagumo, Natsugumo, and Minegumo, employed on training and guard duty. On 15 November 1940 the division joined Destroyer Squadron 4 of the Second Fleet. Koga stayed in the captain’s billet through that change. On 15 October 1941 he was promoted to commander.
At the opening of the Pacific War, Yamagumo flew the flag of Rear Admiral Sueto Hirose, commander of the 3rd Surprise Attack Force. From 26 to 29 November 1941 the division steamed from the Terashima Strait to Mako in the Pescadores. The destroyer left Mako on 7 December at the head of the groups that occupied Batan and Camiguin, north of Luzon, on 10 December. By 22 December she was with the force moving on Lingayen Gulf.
On 31 December 1941, while entering Lingayen Gulf with transports, Yamagumo struck a Japanese mine. Flooded engineering spaces left her dead in the water. Hirose shifted his flag to Manazuru, and the destroyer was brought alongside the transport Yamabiko Maru for emergency repairs. She was taken on to Hong Kong and reached the Yokosuka Naval Arsenal on 7 April 1942. Work continued until 15 May, when she was designated a special-duty ship of the Yokosuka Naval District. Koga remained her captain through that long layoff.
On 20 May 1942 Shiro Ono relieved him, and Koga left to command the destroyer Akizuki. Yamagumo stayed in Ono’s hands. She was sunk in Surigao Strait on 25 October 1944 during the Battle of Leyte Gulf, and Ono was killed aboard her.