Sokuten-class minelayer (1938)

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.

Sokuten-class
Class overview
Name: Sokuten-class minelayer
Builders:
Operators:
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 [1]
  • 2,943,000 JPY in 1939 [2]
  • 4,334,400 JPY in 1941 [3]
  • 4,487,000 JPY in 1942 [4]
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 (23.0 mph; 37.0 km/h)
Range:
  • Nuwajima, 1943
  • approx. 4,000 nmi (7,400 km) at 14 kn (16 mph; 26 km/h)
  • all others
  • 2,000 nmi (3,700 km) at 14 kn (16 mph; 26 km/h)
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

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, 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 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
  1. Senshi Sōsho Vol.31 (1969), p.501
  2. Senshi Sōsho Vol.31 (1969), p.544
  3. Senshi Sōsho Vol.31 (1969), p.815
  4. Senshi Sōsho Vol.88 (1975), p.37
  5. Senshi Sōsho Vol.88 (1975), p.71–74
  6. 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". (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
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