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	Sokuten class
Class overview
Name	Sokuten class
Builders	Hitachi Zōsen Corporation; Mitsubishi Heavy Industries; Mitsui Engineering & Shipbuilding; Nihon Kōkan Corporation; Ōsaka Iron Works; Tama Shipyards; Tōkyō Ishikawajima Shipyard;
Operators	Imperial Japanese Navy; Republic of China Navy;
Preceded by	Natsushima class
Succeeded by	Kamishima class
Subclasses	Sokuten class (Pr. H11); Hirashima class (Pr. H11B); Ajiro class;
Cost	2,540,064 JPY in 1937 ; 2,943,000 JPY in 1939 ; 4,334,400 JPY in 1941 ; 4,487,000 JPY in 1942 ;
Built	1937–1944
In commission	1938–1960
Planned	41
Completed	15
Cancelled	26
Lost	12
Retired	3
	Hirashima class Niizaki on 31 August 1942
General characteristics
Type	Minelayer/Netlayer
Displacement	720 long tons (732 t) standard
Length	74.70 m (245 ft 1 in) overall
Beam	7.85 m (25 ft 9 in)
Draught	Sokuten class; 2.60 m (8 ft 6 in); Hirashima class and Ajiro class; 2.62 m (8 ft 7 in);
Propulsion	2 × MAN Mk.3 Model 10 diesels, 2 shafts, 3,600 bhp
Speed	20.0 knots (37.0 km/h; 23.0 mph)
Range	Nuwajima, 1943; approx. 4,000 nmi (7,400 km; 4,600 mi) at 14 kn (26 km/h; 16 mph); all others; 2,000 nmi (3,700 km; 2,300 mi) at 14 kn (26 km/h; 16 mph);
Complement	Sokuten class and Ajiro class; 74; Hirashima class; 67;
Armament	Sokuten class; 2 × 40 mm heavy machine guns; 2 × Type 93 13 mm AA guns; 36 × Type 95 depth charges; 1 × Type 94 depth charge projector; 10 × depth charge throwers; 1 × Type 93 active sonar; 1 × Type 93 hydrophone; 120 × Type 93 naval mines or 2 × Type 96 510 m (1,673 ft 3 in) anti-submarine nets or 8 × 502.5 m (1,648 ft 7 in) capture nets; Hirashima class and Ajiro class; 1 × 76.2 mm (3.00 in) L/40 AA gun; 2 × Type 93 13 mm AA guns; 36 × Type 95 depth charges; 1 × Type 94 depth charge projector; 10 × depth charge throwers; 1 × Type 93 active sonar; 1 × Type 93 hydrophone; 120 × Type 93 naval mines or 2 × Type 96 510 m anti-submarine nets or 8 × 502.5 m capture nets;

The Sokuten-class minelayer (測天型敷設艇,, Sokuten-gata Fusetsutei) was a class of minelayers of the Imperial Japanese Navy (IJN), serving during and after World War II. The class consists of three subclasses, which this article handles collectively.

Background

In 1937, the IJN planned this class as a replacement for the timeworn Natsushima and the Sokuten-class auxiliary minelayer.

Ships in classes

Sokuten class

Project number H11. Original model of the Sokuten class. Five vessels were built in 1937–40 under the Maru 3 Programme (Ship # 57–61).

Ship #	Ship	Builder	Laid down	Launched	Completed	Fate
57	Sokuten (測天)	Mitsubishi, Yokohama Shipyard	24-06-1937	27-04-1938	28-12-1938	Sunk by aircraft at Palau, 25-07-1944.
58	Shirakami (白神)	Tōkyō Ishikawajima Shipyard	03-09-1937	25-06-1938	25-04-1939	Clashed with Army troop transport and sunk off Urup, 03-03-1944.
59	Naryū (成生)	Mitsubishi, Yokohama Shipyard	24-03-1939	28-08-1939	20-06-1940	Sunk by USS Sennet off Kii Peninsula 32°10′N 135°58′E / 32.167°N 135.967°E / 32.167; 135.967, 16-02-1945.
60	Kyosai (巨済)	Tōkyō Ishikawajima Shipyard	22-06-1938	29-06-1939	27-12-1939	Decommissioned on 05-09-1945. Surrendered to United Kingdom on 20-11-1947. Scrapped on 31-03-1948.
61	Ukishima (浮島)	Tōkyō Ishikawajima Shipyard	28-07-1939	09-12-1939	31-10-1940	Sunk by unknown submarine off Hatsushima, 16-11-1943.

Hirashima class

Project number H11B. Second production model of the Sokuten-class. Nine vessels were built in 1939–43 under the Maru 4 Programme (Ship # 170–178). They were equipped with a 76.2 mm anti-aircraft gun. The Nuwajima had its ballast tank replaced with a fuel tank for convoy escort operations. These nine vessels were classed in the Sokuten-class in the IJN official documents.

Ship #	Ship	Builder	Laid down	Launched	Completed	Fate
170	Hirashima (平島)	Mitsubishi, Yokohama Shipyard	06-09-1939	06-06-1940	24-12-1940	Sunk by USS Sawfish at west of Gotō Islands, 27-07-1943.
171	Hōko (澎湖)	Tama Shipyards	07-11-1940	08-09-1941	20-12-1941	Sunk by aircraft off Buka Island, 28-09-1943.
172	Ishizaki (石埼)	Mitsubishi, Yokohama Shipyard	10-03-1941	13-08-1941	28-02-1942	Decommissioned on 30-11-1945. Surrendered to United States on 01-10-1947. Sunk as target at 35°40′N 122°53′E / 35.667°N 122.883°E / 35.667; 122.883 on 16-10-1947.
173	Takashima (鷹島)	Nihon Kōkan, Tsurumi Shipyard	11-12-1940	18-10-1941	25-03-1942	Sunk by aircraft at Okinawa Island, 10-10-1944.
174	Saishū (済州)	Ōsaka Iron Works, Sakurajima Factory	15-01-1941	15-11-1941	25-04-1942	Decommissioned on 22-10-1945. Surrendered to Republic of China on 03-10-1947, and renamed Yungtsin (PF-75). Decommissioned on 01-05-1960.
175	Niizaki (新井埼)	Mitsui, Tamano Shipyard	12-07-1941	02-03-1942	31-08-1942	Struck a naval mine at Muroran on 04-10-1945. Decommissioned on 05-10-1945. Scrapped 1947.
176	Yurijima (由利島)	Nihon Kōkan, Tsurumi Shipyard	31-10-1941	04-07-1942	25-11-1942	Sunk by USS Cobia off Kota Bharu, 14-01-1945.
177	Nuwajima (怒和島)	Ōsaka Iron Works, Sakurajima Factory	26-11-1941	31-07-1942	15-11-1942	Heavy damaged by aircraft at Saiki, 30-04-1945. Later sank in shallow water. Salvaged and scrapped on 01-09-1948.
178	Maeshima (前島)	Nihon Kōkan, Tsurumi Shipyard	20-07-1942	18-04-1943	31-07-1943	Sunk by aircraft at Laoag City, 21-10-1944.
179	Moroshima (諸島)	Hitachi Zōsen				Cancelled on 11 August 1943.^[5]

Ajiro class

Project number H13 at first. The IJN hoped urgent building for her. The Navy Technical Department revised the Hirashima drawings. Twenty-six vessels were planned under the Maru Kyū Programme (Ship # 460–473, 14 vessels) and the Kai-Maru 5 Programme (Ship # 5421–5432, 12 vessels), but only Ajiro was completed. The Ajiro-class were classified separately from the Sokuten-class in the IJN official documents.

Ship #	Ship	Builder	Laid down	Launched	Completed	Fate
460	Ajiro (網代)	Hitachi Zōsen, Innoshima Shipyard	06-09-1943	08-04-1944	31-07-1944	Sunk by USS Snapper at northwest of Chichi-jima, 01-10-1944.
461–473	Futtsu (富津) Hamizaki (波見埼) Hikoshima (彦島) Himeshima (姫島) Kamishima (神島) Kyobun (巨文) Musō (無双) Niijima (新島) Shinoshima (篠島) Sugashima (菅島) Tateshima (立島) Terajima (寺島) Torai (虎井)					Cancelled on 11 August 1943.^[5]
5421–5432	Arashima (荒島) Awashima (粟島) Hayashima (早島) Hosojima (細島) Kurushima (来島) Makishima (牧島) Michishima (満島) Mishima (見島) Ōshima (大島) Toshima (利島) Tobishima (飛島) Tsunoshima (角島)					Cancelled on 5 May 1944.^[6]

Footnotes

^ Senshi Sōsho Vol.31 (1969), p.501
^ Senshi Sōsho Vol.31 (1969), p.544
^ Senshi Sōsho Vol.31 (1969), p.815
^ Senshi Sōsho Vol.88 (1975), p.37
^ ^a ^b Senshi Sōsho Vol.88 (1975), p.71–74
^ Senshi Sōsho Vol.88 (1975), p.95

Bibliography

"Rekishi Gunzō"., History of Pacific War Vol.51, The truth histories of the Imperial Japanese Vessels Part.2, Gakken (Japan), June 2002, ISBN 4-05-602780-3
Ships of the World special issue Vol.45, Escort Vessels of the Imperial Japanese Navy, "Kaijinsha"., (Japan), February 1996
Model Art Extra No.340, Drawings of Imperial Japanese Naval Vessels Part-1, "Model Art Co. Ltd". Archived from the original on 2012-06-05. Retrieved 2009-05-13. (Japan), October 1989
The Maru Special, Japanese Naval Vessels No.47, Japanese naval mine warfare crafts, "Ushio Shobō". (Japan), January 1981
Daiji Katagiri, Ship Name Chronicles of the Imperial Japanese Navy Combined Fleet, Kōjinsha (Japan), June 1988, ISBN 4-7698-0386-9
Senshi Sōsho Vol.31, Naval armaments and war preparation (1), "Until November 1941", Asagumo Simbun (Japan), November 1969
Senshi Sōsho Vol.88, Naval armaments and war preparation (2), "And after the outbreak of war", Asagumo Simbun (Japan), October 1975