# Junsen type submarine

The Junsen type submarine (巡潜型潜水艦, "巡洋潜水艦", Junsen-gata sensuikan, "Cruiser submarine") was a ship class of submarines of the Imperial Japanese Navy (IJN). There were four submarine designs of the Junsen type: J1, a modified J1, J2 and the J3.

## Class variants

The Junsen type submarines were divided into four classes:
* Junsen I (巡潜一型（伊一型）, Junsen 1-gata, I-1-class)
* Junsen I Mod. (巡潜一型改（伊五型）, Junsen 1-gata Kai, I-5-class)
* Junsen II (巡潜二型（伊六型）, Junsen 2-gata, I-6-class)
* Junsen III (巡潜三型（伊七型）, Junsen 3-gata, I-7-class).

### Junsen I (I-1 class)

Four boats were built in 1923-1929. Genealogy of the large-size submarine in the IJN began with U-142. Japan received six U-boats from Germany as reparations of World War I. The IJN copied U-125, one of the six, producing the I-21-class minelayer submarine. The IJN could not find an optimal design of fleet submarine, so they and Kawasaki Heavy Industries sent many technical officers to the United Kingdom and Germany and got drawings of advanced submarines. The British L class became the Kaidai I, the K class became the Kaidai II and U-142 become Junsen I.
| Boat | Builder | Laid down | Launched | Completed | Results | Fate |
| I-1 | Kawasaki Shipbuilding | 12-03-1923 | 15-10-1924 | 10-03-1926 | Damaged USS Hulbert 31-12-1941 Sank Dutch merchant ship Siantar 03-03-1942 | Sunk by HMNZS Moa and HMNZS Kiwi at Guadalcanal 29-01-1943. |
| I-2 | Kawasaki Shipbuilding | 06-08-1923 | 23-02-1925 | 24-07-1926 | Sank Dutch merchant ship Parigi 01-03-1942 Sank RMS Chilka 11-03-1942 | Sunk by USS Saufley north of Rabaul 02°17′S 149°14′E﻿ / ﻿2.283°S 149.233°E﻿ / -2.283; 149.233 07-04-1944. |
| I-3 | Kawasaki Shipbuilding | 01-11-1924 | 08-06-1925 | 30-11-1926 | Sank RMS Elmdale 07-04-1942 Sank RMS Fultala 08-04-1942 | Sunk by USS PT-59 at Kamimbo 09-12-1942. |
| I-4 | Kawasaki Shipbuilding | 17-04-1926 | 22-05-1928 | 24-12-1929 | Sank Norwegian merchant ship Hoegh Merchant 14-12-1941 Sank Dutch merchant ship Ban Ho Guan 28-02-1942 Sank USS Washingtonian 06-04-1942 Damaged unknown sailing boat 10-04-1942 Damaged USS Alhena 27-09-1942 | Sunk by USS Seadragon southeast of Rabaul 05°02′S 152°33′E﻿ / ﻿5.033°S 152.550°E﻿ / -5.033; 152.550 20-12-1942. |

### Junsen I Mod (I-5 class)

This is a type which added a floatplane to the Junsen I.
| Boat | Builder | Laid down | Launched | Completed | Results | Fate |
| I-5 | Kawasaki Shipbuilding | 30-10-1929 | 19-06-1931 | 31-07-1932 | | Sunk by USS Wyman east of Saipan 13°01′N 151°58′E﻿ / ﻿13.017°N 151.967°E﻿ / 13.017; 151.967 19-07-1944. |

### Junsen II (I-6 class)

Project number S32. This is a type which added a catapult to the Junsen I Mod. She was built in 1931 under the 1st Naval Armaments Supplement Programme (Maru 1).
| Boat | Builder | Laid down | Launched | Completed | Results | Fate |
| I-6 | Kawasaki-Kōbe Shipyard | 14 October 1932 | 31 March 1934 | 15 May 1935 | Damaged aircraft carrier USS Saratoga 11 January 1942 Sank Clan Line cargo ship SS Clan Ross 2 April 1942 Sank RMS Bahadar 7 April 1942 Sank two unknown sailing boats 10 April 1942 | Accidentally rammed, attacked and sunk by Toyokawa Maru northeast of Hachijo-Shima on 16 June 1944. |

### Junsen III (I-7 class)

Project number S33. These boats combined the good points of the Junsen II and the Kaidai V. They were built in 1934 under the Maru 2 Programme. Junsen III became a 'typeship' for the Type-A, B and C.
| Boat | Builder | Laid down | Launched | Completed | Results | Fate |
| I-7 | Kure Naval Arsenal | 12 September 1934 | 3 July 1935 | 31 March 1937 | Sank Dutch merchant ship Le Maire 04-03-1942 Sank RMS Glenshiel 03-04-1942 Sank USS Arcata 15-07-1942 | Damaged by USS Monaghan at Kiska 21 June 1943. Scuttled 5 July 1943. |
| I-8 | Kawasaki-Kōbe Shipyard | 11-10-1934 | 20-07-1936 | 05-12-1938 | Sank Dutch merchant ship Tjisalak 26-03-1944 Sank RMS City of Adelaide 30-03-1944 Sank Australian merchant ship Nellore 29-06-1944 Sank USS Jean Nicolet 02-07-1944 | Sunk by USS Stockton southeast of Okinawa Island 25°29′N 128°35′E﻿ / ﻿25.483°N 128.583°E﻿ / 25.483; 128.583 31-03-1945. |

## Characteristics

| Type | Type | Junsen I (I-1) | Junsen I Mod. (I-5) | Junsen II (I-6) | Junsen III (I-7) |
| Displacement | Surfaced | 1,970 long tons (2,002 t) | same as Junsen I | 1,900 long tons (1,930 t) | 2,231 long tons (2,267 t) |
| Displacement | Submerged | 2,791 long tons (2,836 t) | same as Junsen I | 3,061 long tons (3,110 t) | 3,583 long tons (3,640 t) |
| Length (overall) | Length (overall) | 97.50 m (319 ft 11 in) | same as Junsen I | 98.50 m (323 ft 2 in) | 109.30 m (358 ft 7 in) |
| Beam | Beam | 9.22 m (30 ft 3 in) | same as Junsen I | 9.06 m (29 ft 9 in) | 9.10 m (29 ft 10 in) |
| Draft | Draft | 4.94 m (16 ft 2 in) | same as Junsen I | 5.31 m (17 ft 5 in) | 5.26 m (17 ft 3 in) |
| Depth | Depth | 7.58 m (24 ft 10 in) | same as Junsen I | 7.58 m (24 ft 10 in) | 7.70 m (25 ft 3 in) |
| Power plant and shaft | Power plant and shaft | 2 × Rauschenbach Mk.2 diesels 2 shafts | same as Junsen I | 2 × Kampon Mk.1A Model 7 diesels 2 shafts | 2 × Kampon Mk.1A Model 10 diesels 2 shafts |
| Power | Surfaced | 6,000 bhp | same as Junsen I | 8,000 bhp | 11,200 bhp |
| Power | Submerged | 2,600 shp | same as Junsen I | 2,600 shp | 2,800 shp |
| Speed | Surfaced | 18.8 knots (34.8 km/h) | same as Junsen I | 20.0 knots (37.0 km/h) | 23.0 knots (42.6 km/h) |
| Speed | Submerged | 8.1 knots (15.0 km/h) | same as Junsen I | 7.5 knots (13.9 km/h) | 8.0 knots (14.8 km/h) |
| Range | Surfaced | 24,400 nmi (45,200 km) at 10 knots (19 km/h) | same as Junsen I | 20,000 nmi (37,000 km) at 10 knots (19 km/h) | 14,000 nmi (26,000 km) at 16 knots (30 km/h) |
| Range | Submerged | 60 nmi (110 km) at 3 knots (5.6 km/h) | same as Junsen I | 65 nmi (120 km) at 3 knots (5.6 km/h) | 80 nmi (150 km) at 3 knots (5.6 km/h) |
| Test depth | Test depth | 75 m (246 ft) | same as Junsen I | 80 m (260 ft) | 100 m (330 ft) |
| Fuel | Fuel | 545 tons | 580 tons | 580 tons | 800 tons |
| Complement | Complement | 75 | 75 | 80 | 100 |
| Armament (initial) | Armament (initial) | • 6 × 533 mm (21 in) torpedo tubes (4 × bow, 2 × aft) • 22 × Type 89 torpedoes • 2 × 140 mm (5.5 in) L/40 11th Year Type Naval guns • 1 × 7.7 mm machine gun | • 6 × 533 mm (21 in) torpedo tubes (4 × bow, 2 × aft) • 20 × Type 89 torpedoes • 2 × 127 mm (5.0 in) L/40 Type 88 AA guns • 1 × 7.7 mm machine gun | • 6 × 533 mm (21 in) torpedo tubes (4 × bow, 2 × aft) • 17 × Type 89 torpedoes • 1 × 127 mm (5.0 in) L/40 Type 88 AA gun • 1 × 13.2 mm (0.52 in) AA gun | • 6 × 533 mm (21 in) torpedo tubes (6 × bow) • 20 × Type 89 torpedoes • 2 × 140 mm L/40 11th Year Type Naval guns • 2 × 13 mm AA guns |
| Aircraft and facilities | Aircraft and facilities | | • Hangar • 1 × Yokosuka E6Y1 | • Catapult and hangar • 1 × Yokosuka E6Y1 | • Catapult and hangar • 1 × Watanabe E9W1 Slim |

## Footnotes

* ↑ 伊号第1潜水艦 (I-Gō Dai-1 Sensuikan). The same shall apply hereinafter.
* 1 2 Campbell, John Naval Weapons of World War Two ISBN 0-87021-459-4 p.191