The , also called or 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 .The read as "Sen'yu-Dai", but the read as "Sen'yu-Ō-gata" in Japanese.
The , also called 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 . Their deck guns were removed and fittings for five Kaitens were installed on their decks.
Assigned to the on 24 May 1945, no success.
Assigned to the Todoroki group on 28 May 1945, sank (or damaged) one motor ship on 15 June 1945. Assigned to the on 8 August 1945, no success.
Assigned to the Tamon group on 1 August 1945, no success.
Assigned to the on 5 May 1945, damaged USS Gilligan on 27 May 1945. Assigned to the Tamon group on 19 July 1945, no success.
Assigned to the on 20 February 1945, no success.
Assigned to the Chihaya group on 20 February 1945, no success.
Class variants The Type-D submarines were divided into four classes:
. 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. The same shall apply hereinafter. 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 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 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 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 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 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 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 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,Project Number S60, 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 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
Footnotes
Bibliography
, History of Pacific War Vol.17 I-Gō Submarines, Gakken (Japan), January 1998, , History of Pacific War Vol.36 Kairyū and Kaiten, Gakken (Japan), May 2002, , History of Pacific War Vol.62 Ships of The Imperial Japanese Forces, Gakken (Japan), January 2008, , History of Pacific War Vol.63 Documents of IJN submarines and USN submarines, Gakken (Japan), January 2008, The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III, Ushio Shobō (Japan), September 1980, Book code 68343–43 Senshi Sōsho Vol.88, Naval armaments and war preparation (2), "And after the outbreak of war", Asagumo Simbun (Japan), October 1975
See also Type 4 Ka-Tsu