The were a group of fourteen kaibōkan escort vessels built for the Imperial Japanese Navy during World War II. Eight of the fourteen ships were sunk during the war. The class was also referred to by internal Japanese documents as the .

Background The Shimushu-class kaibōkan, as with the torpedo boat, was a consequence of the 1930 London Naval Treaty, which placed limitations on the total destroyer tonnage the Imperial Japanese Navy was permitted. One way in which the treaty could be circumvented was to use a loophole in the treaty which permitted ships of between 600 and 2,000 tons, with no more than four guns over , no torpedoes, and with a maximum speed of no more than . A new class of vessel was designed to use this loophole, and was given the obsolete designation of kaibōkan (Kai = sea, ocean, Bo = defence, Kan = ship), which had previously been used to designate obsolete battleships which had been reassigned to coastal defense duties. Immediately before the start of then Pacific War, the Imperial Japanese Navy suddenly decided to give more priority to convoy escorts, possibly in light of the ongoing successes of German U-boats against British shipping in the Atlantic. As the Shimushu class was not suited for mass-production and took too long to build, the 1941 Rapid Naval Armaments Supplement Programme authorized thirty modified versions of the Shimushu class, which were designated the Etorofu class. However, sixteen of the projected thirty ships were subsequently re-ordered to the subsequent Mikura, Hiburi or Ukura designs.

Production began between February 1942 and August 1943. Despite simplification, the design was still too complex for mass production and one of the ships was not completed until early 1944.

Description The Etorofu class was almost identical to the Shimushu class but with a simplified bow, stern and bridge structure to facilitate production. The ships measured overall, with a beam of and a draft of .Chesneau, p. 205 They displaced at standard load and at deep load. The ships had two diesel engines, each driving one propeller shaft, which were rated at a total of for a speed of . The ships had a range of at a speed of .Jentschura, Jung & Mickel, p. 187

As with the Shimushu class the main battery of the Etorofu class consisted of three Type 3 guns in single mounts, one superfiring pair aft and one mount forward of the superstructure. Anti-aircraft protection was by four Type 96 anti-aircraft guns in two twin-gun mounts abreast the bridge. However, for a ship supposedly designed for convoy escort, only one Model 94 depth charge launcher was installed on the quarterdeck along with a Model 3 loading frame. The number of depth charges was initially 36, but this was increased to 60 while the ships were still in production, which necessitated the deletion of the two paravanes initially in the design for minesweeping. The ships were also equipped with a Model 93 sonar and a Type 93 hydrophone.

During the Pacific War, the number of Type 96 anti-aircraft gun was increased to five triple-mounts and a varying number of single-mounts, up to 15 in total by August 1943. A Type 22 and Type 13 radar were also installed. A Type 97 trench mortar was also installed front of the bridge

Operational service The Etorofu class proved to be an inadequate design by the time the final units entered service in 1944. Their speed was slower than most submarines, and with only one depth charge projector, their combat capability against the increasingly effective United States Navy submarine forces was ineffective. The Etorofu-class vessels were mostly deployed to the South China Sea or East China Sea as convoy escorts, but few recorded any attacks against Allied submarines. Conversely, six of the 14 ships in the class were sunk by American submarines. Of the six survivors, three were used as repatriation ships after the war, and were subsequently given as prize of war to Allied navies.

Ships in class Thirty ships (numbered #310 to #339) were included in the Rapid Naval Armaments Supplement Programme in 1941. These are listed below with the shipyard to which each was allocated:

Number Name Builder #310 Etorofu Hitachi-Sakurajima Shipyards #311 Matsuwa Mitsui-Tamano Shipyards #312 Sado NKK-Tsurumi Shipyards #313 Oki Uraga Dock Company #314 Matsure Hitachi-Sakurajima Shipyards #315 Iki Mitsui-Tamano Shipyards #316 Tsushima NKK-Tsurumi Shipyards #317 Wakamiya Mitsui-Tamano Shipyards #318 Hirado Hitachi-Sakurajima Shipyards #319 Fukae Uraga Dock Company #320 Mikura NKK-Tsurumi Shipyards #321 Amakusa Hitachi-Sakurajima Shipyards #322 Miyake NKK-Tsurumi Shipyards #323 Manju Mitsui-Tamano Shipyards #324 Awaji Hitachi-Sakurajima Shipyards

Number Name Builder #325 Kanju Uraga Dock Company #326 Nōmi Hitachi-Sakurajima Shipyards #327 Kurahashi NKK-Tsurumi Shipyards #328 Hiburi Hitachi-Sakurajima Shipyards #329 Chiburi NKK-Tsurumi Shipyards #330 Kasado Uraga Dock Company #331 Yashiro Hitachi-Sakurajima Shipyards #332 Ukuru NKK-Tsurumi Shipyards #333 Daitō Hitachi-Sakurajima Shipyards #334 Kusagaki NKK-Tsurumi Shipyards #335 Okinawa NKK-Tsurumi Shipyards #336 Amami NKK-Tsurumi Shipyards #337 Aguni NKK-Tsurumi Shipyards #338 Shinnan Uraga Dock Company #339 Shōnan Hitachi-Sakurajima Shipyards

While fourteen of the above ships were completed to the Etorofu design, eight ships - Mikura (#320), Miyake (#322), Awaji (#324), Nōmi (#326), Kurahashi (#327), Chiburi (#329), Yashiro (#331) and Kusagaki (#334) - were altered to be built to the Mikura design; three ships - Hiburi (#328), Daitō (#333) and Shōnan (#339) - were altered to be built to the Hiburi design; and five ships - Ukuru (#332), Okinawa (#335), Amami (#336), Aguni (#337) and Shinnan (#338) - were altered to be built to the 'Ukuru design. The fourteen completed to the (original) Etorofu design were as follows:

Kanji Name Builder Laid down Launched Completed Fate 択捉 Hitachi-Sakurajima Shipyards 23 February 1942 29 January 1943 15 May 1943 Ceded to the United States, 1946. Scrapped 1947松輪 Mitsui-Tamano Shipyards 20 April 1942 13 November 1942 23 March 1943 Sunk by on 22 August 1944, Hidai Bay, Philippines [14-15N, 120-25E] 佐渡 NKK-Tsurumi Shipyards 21 February 1942 28 November 1942 27 March 1943 Sunk by on 22 August 1944, Hidai Bay, Philippines [14-15N, 120-25E] 隠岐 Uraga Dock Company 27 February 1942 20 October 1942 28 March 1943 Ceded to Republic of China Navy as Gu An (固安) in August 1947, captured by PLAN and renamed Chang Bai (长白) in 1949, scrapped 1982 六連 Hitachi-Sakurajima Shipyards 25 July 1942 10 April 1943 31 July 1943 Sunk by on 2 September 1943, Philippine Sea [08-40N, 151-31E] 壱岐 Mitsui-Tamano Shipyards 2 May 1942 5 February 1943 31 May 1943 Sunk by on 24 May 1944, 150 miles W of Sarawak 対馬 NKK-Tsurumi Shipyards 20 June 1942 20 March 1943 28 July 1943 Ceded to Republic of China Navy as Lin An (臨安) 31 July 1947, scrapped 1963 若宮 Mitsui-Tamano Shipyards 16 July 1942 19 April 1943 10 August 1943 Sunk by on 24 May 1944, East China Sea [28-38N, 122-05E] 平戸 Hitachi-Sakurajima Shipyards 2 November 1942 30 June 1943 28 September 1943 Sunk by on 12 September 1944, South China Sea [17-54N, 114-49] 福江 Often spelled incorrectly Fukue in English literature. Uraga Dock Company 30 October 1942 2 April 1943 28 June 1943 Ceded to UK in July 1947, scrapped 天草 Hitachi-Sakurajima Shipyards 5 April 1943 30 September 1943 20 November 1943 Sunk by Royal Navy aircraft 9 August 1945, Onagawa, Japan 満珠 Mitsui-Tamano Shipyards 15 February 1943 31 July 1943 30 November 1943 Scrapped 1946 干珠 Uraga Dock Company 8 April 1943 7 August 1943 30 October 1943 Scuttled after mine damage, 15 August 1945, near Wonson, Korea [39-10N, 127-27E.] 笠戸 Uraga Dock Company 10 August 1943 9 December 1943 27 February 1944 Scrapped 1948

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External links

Combined Fleet: Etorofu