No.1-class auxiliary minesweeper explained

The was a class of minesweepers of the Imperial Japanese Navy (IJN), serving during World War II. 22 vessels were planned and built in 1941–43 under the Maru Rin Programme (Ship # 251–256) and the Maru Kyū Programme (Ship # 480–495).

Background

• In 1938, the IJN was troubled by drifting contact mines from the National Revolutionary Army at Yangtze River. The IJN dispatched a lot of minesweepers and paravane equipment vessels (minelayers, torpedo boats and more) to Yangtze River, but they were damaged by a drifting contact mines too.
• The IJN wanted a small and light-footed minesweepers. The IJN already commandeered a lot of fishing boats and gave minesweeping operations to them. The Kampon designed minesweeper similar to the trawlers. It is No.1-class auxiliary minesweeper (Project Number I5).
• They have begun to be commissioned from 1942. However, all of them was dispatched to Pacific front, and they were no match for the magnetic mine because their hull was made by steel.

Ships in class

Ship #	Ship	Builder	Laid down	Launched	Completed	Fate
251	Aux. Minesweeper No.1^[1]	Ōsaka Iron Works	30 June 1941	9 November 1941	31 January 1942	Sunk by air raid off Savo Island on 4 May 1942. Decommissioned on 25 May 1942.
252	Aux. Minesweeper No.2	Ōsaka Iron Works	30 June 1941	9 November 1941	28 February 1942	Sunk by air raid off Savo Island on 4 May 1942. Decommissioned on 25 May 1942.
253	Aux. Minesweeper No.3	Ōsaka Iron Works	20 June 1941	31 March 1942	30 May 1942	MIA on 24 July 1945.^[2] Decommissioned on 3 May 1947.
254	Aux. Minesweeper No.4	Naniwa Dock Company	20 June 1941	19 March 1942	29 June 1942	Sunk by air raid off Timor Island -8.6333°N 151°W on 19 July 1944. Decommissioned on 10 September 1944.
255	Aux. Minesweeper No.5	Ōsaka Iron Works	20 June 1941	31 March 1942	30 June 1942	Survived war at Chuuk Islands. Decommissioned in 1947.^[3]
256	Aux. Minesweeper No.6	Naniwa Dock Company	20 February 1942	18 July 1942	30 October 1942	Sunk by air raid at Yamada Bay on 10 August 1945. Decommissioned on 20 October 1945.
480	Aux. Minesweeper No.7	Ōsaka Iron Works	10 February 1942	16 July 1942	28 December 1942	Survived war at Singapore. Surrendered to United Kingdom in July 1946. Decommissioned in 1947.
481	Aux. Minesweeper No.8	Ōsaka Iron Works	10 February 1942	16 July 1942	31 January 1943	Sunk by air raid at Visayan Sea 11.5°N 143°W on 21 October 1944. Decommissioned on 10 May 1945.
482	Aux. Minesweeper No.9	Namura Shipbuilding	20 March 1942	15 August 1942	30 November 1942	Survived war at Singapore. Surrendered to United Kingdom in July 1946. Decommissioned in 1947.
483	Aux. Minesweeper No.10	Sanoyasu Dock Company	3 March 1942	19 August 1942	30 November 1942	Sunk by USN destroyer off Vigan on 12 January 1945. Decommissioned on 10 May 1945.
484	Aux. Minesweeper No.11	Naniwa Dock Company	6 April 1942	30 August 1942	24 February 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to United Kingdom on 14 November 1947.
485	Aux. Minesweeper No.12	Naniwa Dock Company	7 September 1942	27 December 1942	31 March 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to Soviet Union on 3 October 1947.
486	Aux. Minesweeper No.13	Hitachi Zōsen	21 July 1942	25 January 1943	14 April 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to United States on 1 October 1947. Sunk as target at 35.1667°N 175°W on 12 February 1948.^[4]
487	Aux. Minesweeper No.14	Hitachi Zōsen	21 July 1942	25 January 1943	14 May 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to Republic of China on 3 October 1947 and renamed Sao Lei 201. Defected to People's Liberation Army on 17 February 1949 and renamed Qiu Feng. Decommissioned in 1976.
488	Aux. Minesweeper No.15	Namura Shipbuilding	29 August 1942	25 January 1943	30 April 1943	Survived war.^[5] Decommissioned on 30 November 1945.
489	Aux. Minesweeper No.16	Sanoyasu Dock Company	24 August 1942	19 December 1942	31 March 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to United Kingdom on 14 November 1947.
490	Aux. Minesweeper No.17	Naniwa Dock Company	7 September 1942	12 March 1943	28 May 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to Soviet Union on 3 October 1947.
491	Aux. Minesweeper No.18	Namura Shipbuilding	15 February 1943	16 May 1943	31 July 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to United States on 3 October 1947. Sunk as target at 35.2667°N 143°W on 21 January 1948.
492	Aux. Minesweeper No.19	Sanoyasu Dock Company	25 December 1942	25 March 1943	30 June 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to Republic of China on 3 October 1947 and renamed Sao Lei 202. Renamed Jiang Yong (YP-542) in 1952. Decommissioned in 1968. Scrapped.
493	Aux. Minesweeper No.20	Naniwa Dock Company	5 February 1943	27 April 1943	31 July 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to Soviet Union on 3 October 1947.
494	Aux. Minesweeper No.21	Hitachi Zōsen	16 October 1942	11 March 1943	15 June 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to United States on 1 October 1947. Sunk as target at 35.4°N 179°W on 30 October 1947.
495	Aux. Minesweeper No.22	Namura Shipbuilding	20 May 1943	5 July 1943	20 October 1943	Survived war. Decommissioned on 30 November 1945. Surrendered to Republic of China on 3 October 1947 and renamed Sao Lei 203. Renamed Jiang Yi (YP-541) in 1952. Decommissioned in 1968. Scrapped.

Bibliography

• Web site: Rekishi Gunzō., History of Pacific War Vol.51 The truth histories of the Japanese Naval Vessels Part-2, Gakken (Japan), August 2005, .
• Ships of the World special issue Vol.45, Escort Vessels of the Imperial Japanese Navy, Web site: Kaijinsha., (Japan), 1996.
• The Maru Special, Japanese Naval Vessels No.50, Japanese minesweepers and landing ships, Web site: Ushio Shobō. (Japan), 1981.

Notes and References

1. . The same shall apply hereinafter.
2. One opinion: Sunk by USN carrier task force off Surabaya.
3. Detailed date was unidentified.
4. Disposition of U.S. Share of Japanese Naval Vessels, Report on. [File: CNFE/OS-15/L11-3]
5. Another opinion: Exploded and sunk by cause unknown at Jinhae on 14 August 1945.