''I-370'' was an

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender ...

Type D1 transport

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

. Completed and commissioned in September 1944, she served in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

and was converted into a ''

kaiten were crewed torpedoes and suicide craft, used by the Imperial Japanese Navy in the final stages of World War II. History In recognition of the unfavorable progress of the war, towards the end of 1943 the Japanese high command considered s ...

suicide attack A suicide attack is any violent Strike (attack), attack, usually entailing the attacker detonating an explosive, where the attacker has suicide, accepted their own death as a direct result of the attacking method used. Suicide attacks have oc ...

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...

carrier in January 1945. She was sunk in February 1945 while operating during the

Battle of Iwo Jima The Battle of Iwo Jima (19 February – 26 March 1945) was a major battle in which the United States Marine Corps (USMC) and United States Navy (USN) landed on and eventually captured the island of Iwo Jima from the Imperial Japanese Army (IJ ...

Construction and commissioning

''I-370'' was

laid down Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship. Keel laying is one o ...

on 4 December 1943 by

Mitsubishi The is a group of autonomous Japanese multinational companies in a variety of industries. Founded by Yatarō Iwasaki in 1870, the Mitsubishi Group historically descended from the Mitsubishi zaibatsu, a unified company which existed from 1870 ...

Kobe Kobe ( , ; officially , ) is the capital city of Hyōgo Prefecture Japan. With a population around 1.5 million, Kobe is Japan's seventh-largest city and the third-largest port city after Tokyo and Yokohama. It is located in Kansai region, whic ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, with the name ''Submarine No. 5470''. She was launched on 26 May 1944 and renamed ''I-370'' that day. She was completed and commissioned on 4 September 1944.

Service history

Upon commissioning, ''I-370'' was attached to the

Sasebo Naval District was the third of five main administrative districts of the pre-war Imperial Japanese Navy. Its territory included the western and southern coastline of Kyūshū, the Ryukyu Islands, Taiwan and Korea, as well as patrols in the East China Sea and t ...

and was assigned to Submarine

Squadron Squadron may refer to: * Squadron (army), a military unit of cavalry, tanks, or equivalent subdivided into troops or tank companies * Squadron (aviation), a military unit that consists of three or four flights with a total of 12 to 24 aircraft, de ...

11 for workups. In January 1945, she was converted from a transport submarine into a ''

carrier, the conversion involving the removal of her and ''Daihatsu''-class

landing craft Landing craft are small and medium seagoing watercraft, such as boats and barges, used to convey a landing force (infantry and vehicles) from the sea to the shore during an amphibious assault. The term excludes landing ships, which are larger. Pr ...

and their replacement with fittings allowing her to carry five ''kaitens'' on her deck, as well as the installation of Type 22 surface-search

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

. On 10 January 1945, she and the submarine took part in simulated ''kaiten'' attacks against

towed Towing is coupling two or more objects together so that they may be pulled by a designated power source or sources. The towing source may be a motorized land vehicle, vessel, animal, or human, and the load being anything that can be pulled. Th ...

targets in the

Seto Inland Sea The , sometimes shortened to the Inland Sea, is the body of water separating Honshū, Shikoku, and Kyūshū, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka ...

that lasted 15 days. The

began on 19 February 1945 when U.S. forces landed on

Iwo Jima Iwo Jima (, also ), known in Japan as , is one of the Japanese Volcano Islands and lies south of the Bonin Islands. Together with other islands, they form the Ogasawara Archipelago. The highest point of Iwo Jima is Mount Suribachi at high. ...

. The Japanese formed the ''Chihaya'' ''Kaiten'' Group, made up of , , and the submarine , with orders to proceed to the waters off Iwo Jima and attack American ships there. On 21 February 1945, ''I-370'' got underway from the ''kaiten'' base at

Hikari may refer to: Places *Hikari Station, a station on Sanyō Main Line in Hikari, Yamaguchi * Hikari, Chiba, a former town in Sousa District, Chiba, Japan *Hikari, Yamaguchi, a city in Yamaguchi Prefecture, Japan People *Hikari (name), people and ...

and set course for Iwo Jima, where she was expected to begin ''kaiten'' attacks on 26 February 1945. ''I-370'' was on the surface just after dawn on 26 February 1945 preparing to launch all five of her ''kaitens'' to attack nine empty American transports steaming from Iwo Jima to

Saipan Saipan ( ch, Sa’ipan, cal, Seipél, formerly in es, Saipán, and in ja, 彩帆島, Saipan-tō) is the largest island of the Northern Mariana Islands, a Commonwealth (U.S. insular area), commonwealth of the United States in the western Pa ...

when one of their escorts, the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

destroyer escort Destroyer escort (DE) was the United States Navy mid-20th-century classification for a warship designed with the endurance necessary to escort mid-ocean convoys of merchant marine ships. Development of the destroyer escort was promoted by th ...

, detected her on radar. ''Finnegan'' closed the range. Eight minutes after ''Finnegan'' detected ''I-370'', crash-dived and broke radar contact with ''Finnegan'', but at 0659 ''Finnegan'' acquired ''I-370'' on

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...

. ''Finnegan'' launched an unsuccessful

Hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introducti ...

attack, followed by a pattern of 13

depth charge A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive Shock factor, hydraulic shock. Most depth ...

s set to explode deep. She launched another Hedgehog attack, then dropped a pattern of 13 depth charges set for medium depth at around 10:00. At around 10:05, ''Finnegan''′s crew heard a deep rumbling sound, then observed air bubbles reaching the surface followed by an explosion. It marked the end of ''I-370'', sunk with the loss of all 84 men on board — her entire crew of 79 and all five embarked ''kaiten'' pilots — at . She was both the first submarine of the ''Chihaya'' Group and the first transport submarine converted into a ''kaiten'' carrier to be lost. A

fuel oil Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bun ...

slick at the scene of her sinking eventually covered an area of . On 6 March 1945, the Japanese ordered ''I-370'' to return to Japan, but she never acknowledged the order. On 14 March 1945, the Imperial Japanese Navy declared ''I-370'' to be presumed lost with all hands off Iwo Jima. She was stricken from the Navy list on 10 April 1945.

Notes

Sources

* Hackett, Bob & Kingsepp, Sander.
IJN Submarine I-370: Tabular Record of Movement
Retrieved on September 16, 2020. {{DEFAULTSORT:I-370 Type D submarines Ships built by Mitsubishi Heavy Industries 1944 ships World War II submarines of Japan Japanese submarines lost during World War II Maritime incidents in February 1945 Ships lost with all hands World War II shipwrecks in the Pacific Ocean Submarines sunk by United States warships