# Type D submarine

The I-361 class submarine (伊三百六十一型潜水艦, I-san-byaku-roku-jū-ichi-gata Sensuikan), also called Type-D submarine (丁型/潜丁型潜水艦, Tei-gata/Sen-Tei-gata sensuikan) or Sen'yu/Sen'yu-Dai type submarine (潜輸型/潜輸大型潜水艦, Sen'yu-gata/Sen'yu-Ōgata sensuikan) was a type of the 1st class submarine in the Imperial Japanese Navy serving during the Second World War. The type name, was shortened to Yusō Sensuikan Ō-gata (輸送潜水艦大型, Transport Submarine-Large Type).
The I-373 class submarine (伊三百七十三型潜水艦, I-san-byaku-nana-jū-san-gata Sensuikan), also called Type-D Modified submarine (丁型改潜水艦, Tei-gata Kai sensuikan) was different from the I-361 class, however since the I-373 was a development form of the I-361 class, this article describes both of them.

## Construction

After the Battle of Midway the IJN immediately planned a transport submarine. The type was based on the U 155 Deutschland. Her duties were transportation of troops (110 men, 10 tons freight and two landing craft) in the areas where the enemy had air superiority. Later the demands for her were changed in sequence. The final demands were 65 tons in the hull and 25 tons on the upper deck (freight only). In the beginning the IJN did not intend to arm these boats with torpedoes. Later, after strong demands from the front commanders, it was decided to arm them with torpedoes for self-defense. The I-372 class was designed as a tanker submarine based on the I-361 class. They were not allowed to be loaded with torpedoes.

## Service

In 1944, the submarines were tasked with transport missions between from mainland Japan to remote islands. They had little success and suffered great losses. Of the 13 submarines, only four survived the war.

## Kaiten missions

In 1945, several submarines were converted to be Kaiten mother ships and assigned to the suicide attack operations for the Shinchō Tokubetsu Kōgekitai (神潮特別攻撃隊, Sinchō Special Attack Force). Their deck guns were removed and fittings for five Kaitens were installed on their decks.
* I-361
** Assigned to the Todoroki group (轟隊) on 24 May 1945, no success.
* I-363
** Assigned to the Todoroki group on 28 May 1945, sank (or damaged) one motor ship on 15 June 1945.
** Assigned to the Tamon group (多聞隊) on 8 August 1945, no success.
* I-366
** Assigned to the Tamon group on 1 August 1945, no success.
* I-367
** Assigned to the Shinbu group (振武隊) on 5 May 1945, damaged USS Gilligan on 27 May 1945.
** Assigned to the Tamon group on 19 July 1945, no success.
* I-368
** Assigned to the Chihaya group (千早隊) on 20 February 1945, no success.
* I-370
** Assigned to the Chihaya group on 20 February 1945, no success.
* I-363 in May or August 1945
* I-367 on 19 July 1945
* I-370 on 21 February 1945

## Class variants

The Type-D submarines were divided into four classes:
* Type-D/Sen'yu (丁型/潜輸（伊三百六十一型）, Tei-gata/Sen'yu, I-361-class)
* Type-D/Sen'yu Mod. (丁型/潜輸改（伊三百七十二型）, Tei-gata/Sen'yu-Kai, I-372-class)
* Type D Mod. (丁型改（伊三百七十三型）, Tei-gata Kai, I-373-class)
* Type D Mod.2/Type D 2 (S60 Type) (丁型改2/潜丁2型（第2968号艦型）, Tei-gata Kai-2/Sen-Tei-2-gata, 2968th vessel-class (Dai-2968-Gō kan-gata)). The 2968th vessel class boats were not built and remained only a design.

### I-361 class

| Boat # | Name | Builder | Laid down | Launched | Completed | Fate |
| 5461 | I-361 | Kure Naval Arsenal | 16 February 1943 | 30 October 1943 | 25 May 1944 | Converted to a Kaiten mother ship on 7 February 1945. Sunk by aircraft from USS Anzio at east of Okinawa Island 22°22′N 134°09′E﻿ / ﻿22.367°N 134.150°E﻿ / 22.367; 134.150 on 30 May 1945. |
| 5462 | I-362 | Mitsubishi, Kōbe Shipyard | 17 March 1943 | 29 November 1943 | 23 May 1944 | Sunk by USS Fleming at Caroline Islands 12°08′N 130°28′E﻿ / ﻿12.133°N 130.467°E﻿ / 12.133; 130.467 on 18 January 1945. |
| 5463 | I-363 | Kure Naval Arsenal | 1 May 1943 | 12 December 1943 | 8 July 1944 | Converted to a Kaiten mother ship on 30 March 1945. Sunk by naval mine off Miyazaki on 29 October 1945. Salvaged and scrapped on 26 January 1966. |
| 5464 | I-364 | Mitsubishi, Kōbe Shipyard | 26 July 1943 | 15 February 1944 | 14 June 1944 | Sunk by USS Sea Devil at Bōsō Peninsula 34°30′N 145°23′E﻿ / ﻿34.500°N 145.383°E﻿ / 34.500; 145.383 on 15 September 1944. |
| 5465 | I-365 | Yokosuka Naval Arsenal | 15 May 1943 | 17 December 1943 | 1 August 1944 | Sunk by USS Scabbardfish at Tōkyō Bay 34°44′N 141°01′E﻿ / ﻿34.733°N 141.017°E﻿ / 34.733; 141.017 on 28 November 1944. |
| 5466 | I-366 | Mitsubishi, Kōbe Shipyard | 26 August 1943 | 29 March 1944 | 3 August 1944 | Converted to a Kaiten mother ship on 3 March 1945. Decommissioned on 30 November 1945. Sunk as target off Gotō Islands on 1 April 1946. |
| 5467 | I-367 | Mitsubishi, Kōbe Shipyard | 22 October 1943 | 28 April 1944 | 15 August 1944 | Converted to a Kaiten mother ship on 1 January 1945. Decommissioned on 30 November 1945. Sunk as target off Gotō Islands on 1 April 1946. |
| 5468 | I-368 | Yokosuka Naval Arsenal | 15 July 1943 | 29 January 1944 | 25 August 1944 | Converted to a Kaiten mother ship in early 1945. Sunk by aircraft from USS Anzio at west of Iwo Jima 24°07′N 140°19′E﻿ / ﻿24.117°N 140.317°E﻿ / 24.117; 140.317 on 27 February 1945. |
| 5469 | I-369 | Yokosuka Naval Arsenal | 1 September 1943 | 9 March 1944 | 9 October 1944 | Converted to a tanker submarine in June 1945; decommissioned on 15 September 1945. Surrendered to United States at Yokosuka, later scrapped. |
| 5470 | I-370 | Mitsubishi, Kōbe Shipyard | 4 December 1943 | 26 May 1944 | 4 September 1944 | Converted to a Kaiten mother ship in early 1945. Sunk by USS Finnegan at south of Iwo Jima 22°45′N 141°27′E﻿ / ﻿22.750°N 141.450°E﻿ / 22.750; 141.450 on 26 February 1945. |
| 5471 | I-371 | Mitsubishi, Kōbe Shipyard | 22 March 1944 | 21 July 1944 | 2 October 1944 | Sunk by USS Lagarto at Bungo Channel 32°40′N 132°33′E﻿ / ﻿32.667°N 132.550°E﻿ / 32.667; 132.550 on 24 February 1945. |

### I-372 class

Project number S51B. She was going to become a lead ship of the Modified Type D submarines (I-373 class), at first. However, the IJN wanted a submarine as soon as possible. She was built as a tanker submarine according to revised I-361 drawings.
| Boat # | Name | Builder | Laid down | Launched | Completed | Fate |
| 2961 | I-372 | Yokosuka Naval Arsenal | 10 February 1944 | 22 June 1944 | 8 November 1944 | Sunk by USN carrier aircraft from Task Force 38 at Yokosuka on 18 July 1945. I-372 was raised, towed to deep water, and scuttled in August 1946. |

### I-373 class

Project number S51C. Improved model of the I-361 class. Furthermore, the IJN was planned reinforced model of the I-373 class, also. However all of them were cancelled.
| Boat # | Name | Builder | Laid down | Launched | Completed | Fate |
| 2962 | I-373 | Yokosuka Naval Arsenal | 15 August 1944 | 30 November 1944 | 14 April 1945 | Converted to a tanker submarine in June 1945; sunk by USS Spikefish at East China Sea 29°02′N 123°53′E﻿ / ﻿29.033°N 123.883°E﻿ / 29.033; 123.883 on 13 August 1945. |
| 2963 | I-374 | Yokosuka Naval Arsenal | 24 October 1944 | | | Construction stopped on 17 April 1945 (40% complete), later scrapped. |
| 2964 | I-375 | | | | | Cancelled on 17 April 1945. |
| 2965 - 2967 | | | | | | Cancelled on 17 April 1945. |

## Footnotes

* ↑ Senshi Sōsho Vol.88 (1975), p.50–51
* ↑ Senshi Sōsho Vol.88 (1975), p.94–95
* 1 2 3 4 Senshi Sōsho Vol.88 (1975), p.272–273
* ↑ Campbell, John Naval Weapons of World War Two ISBN 0-87021-459-4 p. 191
* ↑ The 潜輸大 read as "Sen'yu-Dai", but the 潜輸大型 read as "Sen'yu-Ō-gata" in Japanese.
* ↑ 伊号第361潜水艦 (I-Gō Dai-361 Sensuikan). The same shall apply hereinafter.
* ↑ Project Number S60, Type D II submarine (潜丁2型, Sen Tei Ni-Gata)