Japanese submarine Ha-204

At the end of 1944, the Imperial Japanese Navy decided it needed large numbers of high-speed coastal submarines to defend the Japanese Home Islands[1] against an anticipated Allied invasion (named Operation Downfall by the Allies). To meet this requirement, the Ha-201-class submarines were designed as small, fast submarines[1] incorporating many of the same advanced ideas implemented in the German Type XXI and Type XXIII submarines. They were capable of submerged speeds of almost 14 knots (26 km/h; 16 mph).[1]

The Ha-201 class displaced 325 metric tons (320 long tons) surfaced and 447 metric tons (440 long tons) submerged.[1] The submarines were 53 meters (173 ft 11 in) long, had a beam of 4.00 meters (13 ft 1 in) and a draft of 3.44 meters (11 ft 3 in).[1] For surface running, the submarines were powered by a single 400-brake-horsepower (298 kW) diesel engine that drove one propeller shaft.[1] When submerged the propeller was driven by a 1,250-shaft-horsepower (932 kW) electric motor.[1] They could reach 11.8 knots (21.9 km/h; 13.6 mph) on the surface and 13.9 knots (25.7 km/h; 16.0 mph) submerged.[1] On the surface, the Ha-201-class submarines had a range of 3,000 nautical miles (5,600 km; 3,500 mi) at 10 knots (19 km/h; 12 mph); submerged, they had a range of 105 nmi (194 km; 121 mi) at 2 knots (3.7 km/h; 2.3 mph).[1] Their armament consisted of two 533-millimeter (21 in) torpedo tubes with four torpedoes and a single mount for a 7.7-millimeter machine gun.[1]

Ha-204 (left) with the submarines Ha-203 (center) and Ha-109 (right) at Kure, Japan, on 16 October 1945.

Ha-204 was laid down on 5 April 1945 by the Sasebo Naval Arsenal at Sasebo, Japan, as Submarine No. 4914.[2] She was renamed Ha-204 on 1 May 1945 and was attached provisionally to the Sasebo Naval District that day.[2] Launched on 1 June 1945,[2] she was completed and commissioned on 25 June 1945.[2]

Upon commissioning, Ha-204 was attached formally to the Sasebo Naval District and assigned to Submarine Division 33 in the Kure Submarine Flotilla for workups.[2] While she was underway off Etajima on her way to Kure, Japan, for a hull refit on 6 August 1945, the United States Army Air Forces B-29 Superfortress Enola Gay dropped an atomic bomb on nearby Hiroshima.[2] The detonation of the atomic bomb at 08:15 inflicted severe radiation burns on Ha-204′s bridge crew, including her commanding officer.[2]

Ha-204 had not yet conducted an operational patrol when hostilities between Japan and the Allies ended[1] on 15 August 1945. She surrendered to the Allies at Sasebo on 2 September 1945.[2] She ran aground in Aburatsu Bay on the coast of Miyazaki Prefecture on Kyushu on 29 October 1945.[2]

The Japanese struck Ha-204 from the Navy list on 30 November 1945.[2] Her wreck eventually was salvaged, and it was scrapped between August and October 1948 at the Nishimura Tekkosho ironworks plant.[2]

• Hackett, Bob; Kingsepp, Sander (2019). "IJN Submarine HA-204: Tabular Record of Movement". SENSUIKAN! Stories and Battle Histories of the IJN's Submarines. Combinedfleet.com. Retrieved 9 October 2020.
• Hackett, Bob; Sander Kingsepp (2015). "Sen Taka Sho Type". Sensuikan!. Combinedfleet.com. Retrieved 9 October 2020.
• "Rekishi Gunzō"., History of Pacific War Vol.17 I-Gō Submarines, Gakken (Japan), January 1998, ISBN 4-05-601767-0
• Rekishi Gunzō, History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005, ISBN 4-05-603890-2
• The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III, Ushio Shobō (Japan), September 1980, Book code 68343-43
• The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition", Ushio Shobō (Japan), February 1988, Book code 68344-36
• Ships of the World special issue Vol.37, History of Japanese Submarines, "Kaijinsha"., (Japan), August 1993