In 1939 the Imperial Japanese Navy had two diesel-engined harbour tugs built, No.1182 and No.1183. (Other contemporary Japanese harbour tugs were powered by
compound steam engines). They had wooden hulls and were designed so that they could be converted to fishing boats after hostilities ended.[1] The two tugs, which were completed in 1940,[2] formed the basis for a class of auxiliary subchasers.
The IJN evaluated them, confirmed that they were effective subchasers, and in 1941, ordered 100 vessels. Their wartime performance was good, but they were always troubled by insect damage because their hull was wooden. Those that survived the war played an active part in the
sweeping of magnetic mines in company with the
No.1-class auxiliary patrol boats.
Aux. Submarine Chaser No.1, completed on 27 March 1943, survived war. Transferred to Japan Maritime Safety Agency as patrol boat and renamed Chidori (PS-18) on 1 May 1948. Later renumbered PS-134. Discarded 1960.[3][4]
Aux. Submarine Chaser No.4, completed on 18 April 1943, survived war. Transferred to Japan Maritime Safety Agency and renamed Kiji (PB-20) on 1 May 1948. Renumbered NS 81 in 1953. Discarded 1959.[3][5]
Aux. Submarine Chaser No.27, completed on 10 July 1943, survived war. Transferred to Japan Maritime Safety Agency and renamed Tsubame (PS-23) on 1 May 1948. Discarded 1952.[3]
Aux. Submarine Chaser No.57, completed on 30 October 1943, survived war. Transferred to Japan Maritime Safety Agency as patrol boat and renamed Kawasemi (PS-21) on 1 May 1948. Later renumbered PS 136. Discarded 1957.[3]
Aux. Submarine Chaser No.58, completed on 16 November 1943, survived war. Transferred to Japan Maritime Safety Agency as patrol boat and renamed Uzura (PS-32) on 1 May 1948. Renumbered PS 140 later and discarded 1960.[3]
Aux. Submarine Chaser No.71, completed on 30 October 1943, survived war. Transferred to Japan Maritime Safety Agency as patrol boat and renamed Hōjiro (PS-39) on 1 May 1948. Discarded 1964.[3]
Aux. Submarine Chaser No.72, completed on 20 December 1943, survived war. Transferred to Japan Maritime Safety Agency as minesweeper and renamed Umitsubame (MS 07) on 1 May 1948. To Maritime Self Defense Force 1954. Renumbered MSI 697. Transferred to harbour service 1961.[3]
Aux. Submarine Chaser No.78, completed on 15 October 1943, survived war. Transferred to Japan Maritime Safety Agency and renamed Ōtori (PS-28) on 1 May 1948. Redesignated MS 82 1953. Transferred to Maritime Self Defense Force 1954. Discarded 1959[3]
Aux. Submarine Chaser No.79, completed on 26 February 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 08 on 1 May 1948.
Aux. Submarine Chaser No.80, completed on 15 December 1943, survived war. Transferred to Japan Maritime Safety Agency and renamed Sekirei (PB-08) on 1 May 1948.
Aux. Submarine Chaser No.153, completed on 19 April 1944, struck a naval mine and sunk in shallow water on 6 July 1945.
Aux. Submarine Chaser No.154, completed on 24 April 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Uguisu (PB-06) on 1 May 1948.
Aux. Submarine Chaser No.155, completed on 25 April 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Shigi (PB-26) on 1 May 1948.
Aux. Submarine Chaser No.157, completed on 20 April 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Aosagi (PB-37) on 1 August 1948.
Aux. Submarine Chaser No.158, completed on 24 April 1944, survived war. Sold to Ministry of Education on 25 May 1948.
Aux. Submarine Chaser No.159, completed on 17 May 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Hinazuru (PB-38) on 1 August 1948.
Aux. Submarine Chaser No.161, completed on 3 July 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Kotaka (PB-24) on 1 May 1948.
Aux. Submarine Chaser No.166, completed on 10 June 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Hato (PB-17) on 1 May 1948.
Aux. Submarine Chaser No.168, completed on 6 July 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 57 on 1 May 1948.
Aux. Submarine Chaser No.169, completed on 31 May 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Yamasemi (PB-11) on 1 May 1948.
Aux. Submarine Chaser No.173, completed on 30 May 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Shirataka (PB-40) on 1 August 1948.
Aux. Submarine Chaser No.175, completed on 9 August 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Kasasagi (PB-01) on 1 May 1948.
Aux. Submarine Chaser No.179, completed on 30 May 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Yamagara (PB-41) on 1 August 1948.
Aux. Submarine Chaser No.181, completed on 15 June 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Hibari (PB-16) on 1 May 1948.
Aux. Submarine Chaser No.183, completed on 3 July 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Benizuru (PB-12) on 1 May 1948.
Aux. Submarine Chaser No.185, completed on 3 September 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Hayabusa (PB-19) on 1 May 1948.
Aux. Submarine Chaser No.186, completed on 4 September 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Hatsukari (PB-13) on 1 May 1948.
Aux. Submarine Chaser No.187, completed on 3 June 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Yamadori (PB-04) on 1 May 1948.
Aux. Submarine Chaser No.194, completed on 21 August 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Mizutori (PB-42) on 1 May 1948.
Aux. Submarine Chaser No.196, completed on 15 October 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Wakataka (PB-25) on 1 May 1948.
Aux. Submarine Chaser No.202, completed on 1 September 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 14 on 1 May 1948. Sunk off Wonsan Korea during minesweeping operations on 17 October 1950.
Aux. Submarine Chaser No.203, completed on 14 October 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Hiyodori (PB-22) on 1 May 1948.
No.2064 vessel (Aux. Submarine Chaser No.214), transferred to Karafuto Prefecture, before completed.
Aux. Submarine Chaser No.214, substitution of the No.2064 vessel, completed on 8 December 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 15 on 1 May 1948.
Aux. Submarine Chaser No.215, completed on 15 August 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 16 on 1 May 1948.
Aux. Submarine Chaser No.217, completed on 6 December 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Tsugumi (PB-07) on 1 May 1948.
Aux. Submarine Chaser No.219, completed on 9 November 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Shirasagi (PB-14) on 1 May 1948.
Aux. Submarine Chaser No.220, completed on 28 December 1944, survived war. Captured by Republic of China in 1945, betrayed to People's Republic of China in 1949.
Aux. Submarine Chaser No.221, completed on 28 August 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 02 on 1 May 1948.
Aux. Submarine Chaser No.222, completed on 1 November 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 03 on 1 May 1948.
Aux. Submarine Chaser No.223, completed on 25 November 1944, survived war. Captured by Republic of China in 1945, betrayed to People's Republic of China in 1949.
Aux. Submarine Chaser No.231, completed on 7 December 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 17 on 1 May 1948.
Aux. Submarine Chaser No.232, completed on 31 December 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Ōtaka (PB-09) on 1 May 1948.
Aux. Submarine Chaser No.245, completed on 5 November 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed Manazuru (PB-03) on 1 May 1948.
Aux. Submarine Chaser No.246, completed on 22 January 1945, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 05 on 1 May 1948.
Aux. Submarine Chaser No.249, completed on 14 November 1944, survived war. Transferred to Japan Maritime Safety Agency and renamed MS 06 on 1 May 1948.
Gardiner, Robert and Stephen Chumbley. Conway's All The World's Fighting Ships 1947–1995. Annapolis, Maryland, USA: Naval Institute Press, 1995.
ISBN1-55750-132-7.
Jentschura, Hansgeorg, Dieter Jung and Peter Michel. Warships of the Imperial Japanese Navy, 1869–1945, Annapolis, Maryland, USA: Naval Institute Press, 1977.
ISBN0-87021-893-X
Ships of the World special issue Vol.45, Escort Vessels of the Imperial Japanese Navy, Kaijinsha, (Japan), February 1996
The Maru Special-Japanese Naval Vessels No.49, Japanese submarine chasers, Ushio Shobō (Japan), March 1981