''Ro-31'', originally named ''Submarine No. 70'', 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 ...

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 ...

of the ''Kaichu'' V (''Toku Chu'') subclass. After a diving accident in 1923 prior to completion, she was salvaged, rebuilt, and completed in 1927. She served in a training role during

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 ...

, surrendered at the end of the war in September 1945, and was

scuttled Scuttling is the deliberate sinking of a ship. Scuttling may be performed to dispose of an abandoned, old, or captured vessel; to prevent the vessel from becoming a navigation hazard; as an act of self-destruction to prevent the ship from being ...

in April 1946.

Design, description and construction

The submarines of the ''Kaichu'' V sub-class were designed for anti-shipping operations and carried more fuel and had greater range and a heavier gun armament than preceding ''Kaichu''-type submarines. They displaced surfaced and submerged. The submarines were long and had a

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...

of and a

draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vesse ...

of . They had a diving depth of . For surface running, the submarines were powered by two Sulzer

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...

s, each driving one

propeller shaft A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power and torque and rotation, usually used to connect ...

. When submerged each propeller was driven by a

electric motor An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...

. They could reach on the surface and underwater. On the surface, they had a range of — although the Imperial Japanese Navy officially announced it as — at ; submerged, they had a range of at . The submarines were armed with four internal bow

torpedo tube A torpedo tube is a cylindrical device for launching torpedoes. There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units (also referred to as torpedo launchers) installed aboa ...

s and carried a total of eight

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 ...

es. They were also armed with a single deck gun and one 6.5 mm

machine gun A machine gun is a fully automatic, rifled autoloading firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles (including assault rifles and battle rifles) a ...

. ''Ro-31'' 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 ...

as ''Submarine No. 70'' on 25 September 1921 by Kawasaki at

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 ...

, and was launched on 15 February 1923.

Accident, salvage and commissioning

On 21 August 1923, and accidental sinking during sea trials killed 88 men — 46 Imperial Japanese Navy personnel and 42 shipyard workers — out of 93 on board. Five men survived the sinking. Her

commanding officer The commanding officer (CO) or sometimes, if the incumbent is a general officer, commanding general (CG), is the officer in command of a military unit. The commanding officer has ultimate authority over the unit, and is usually given wide latitu ...

was among the survivors, and on 14 March 1924 he was found responsible for the loss of his submarine and fined 100

yen The is the official currency of Japan. It is the third-most traded currency in the foreign exchange market, after the United States dollar (US$) and the euro. It is also widely used as a third reserve currency after the US dollar and the e ...

. Just after completing a pre-completion diving test and submerged

sea trial A sea trial is the testing phase of a watercraft (including boats, ships, and submarines). It is also referred to as a " shakedown cruise" by many naval personnel. It is usually the last phase of construction and takes place on open water, and ...

off Kobe, she assumed a 30-degree down-angle by the bow and sank 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 ...

off Kariya Point on Awaji Island when a hatch was opened prematurely, the wake of a passing ship swamped her, and the mismanagement of various valves caused her crew to lose control of her."Submarine Accidents Involving Loss of Life Since World War," Navy Appropriation Bill for 1929, Seventieth Congress of the United States, Washington, D.C.: Government Printing Office, 1928, p. 107.
/ref>''Airship Investigation: Report of Col. Henry Breckenridge'', Washington, D.C.: Government Printing Office, 1933, p. 55.
/ref> ''Submarine No 70'' was refloated on 24 October 1924 and dismantled. She was laid down again on 20 December 1924 to be rebuilt with the materials used in her original construction. She was relaunched on 25 September 1926 and 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 ...

the same day. She was completed and commissioned on 10 May 1927 and was renamed ''Ro-31'' that day.

Service history

Pre-World War II

Upon commissioning, ''Ro-31'' was attached to the

, to which she remained attached throughout the pre-

period. On 15 November 1934, she was reassigned to Submarine Division 25. She was decommissioned and placed in the Fourth Reserve on 15 December 1938.

World War II

''Ro-31'' was still in reserve when the Pacific Campaign of

began on 7 December 1941 (8 December 1941 in

East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea and ...

) with the Japanese

attack on Pearl Harbor The attack on Pearl HarborAlso known as the Battle of Pearl Harbor was a surprise military strike by the Imperial Japanese Navy Air Service upon the United States against the naval base at Pearl Harbor in Honolulu, Territory of Hawaii, j ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

. She was recommissioned on 9 February 1942 to serve as a training submarine, initially attached to the

Kure Naval District was the second of four main administrative districts of the pre-war Imperial Japanese Navy. Its territory included the Seto Inland Sea, Inland Sea of Japan and the Pacific Ocean, Pacific coasts of southern Honshū from Wakayama prefecture, Wakayam ...

beginning on the day she was recommissioned, then to the

Yokosuka Naval District was the first of four main administrative districts of the pre-war Imperial Japanese Navy. Its territory included Tokyo Bay and the Pacific Ocean, Pacific coasts of central and northern Honshū from the Kii Peninsula to Shimokita Peninsula. Its h ...

from 14 July 1942 to 15 January 1943, and then to the Kure Naval District again until 15 January 1944, when she again was decommissioned and placed in the Fourth Reserve in the Kure Naval District. The Japanese struck her from the Navy list on 25 May 1945.

Disposal

''Ro-31'' was on the Japanese coast in the western Seto Inland Sea awaiting disposal when hostilities between Japan and the

Allies An alliance is a relationship among people, groups, or states that have joined together for mutual benefit or to achieve some common purpose, whether or not explicit agreement has been worked out among them. Members of an alliance are called ...

ended on 15 August 1945. She surrendered to the Allies on 2 September 1945. 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 ...

her along with the Japanese submarines , , , , , , and off

Sasebo Bay is a Core cities of Japan, core city located in Nagasaki Prefecture, Japan. It is also the second largest city in Nagasaki Prefecture, after its capital, Nagasaki. On 1 June 2019, the city had an estimated population of 247,739 and a population de ...

on 5 April 1946.

Notes

References

*'', History of Pacific War Vol.17 I-Gō Submarines'',

Gakken is a Japanese publishing company founded in 1947 by Hideto Furuoka, which also produces educational toys. Their annual sales is reported at ¥ 90 billion ($789 million US). Gakken publishes educational books and magazines and produces other ...

(Japan), January 1998, *''Rekishi Gunzō, History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces"'', Gakken (Japan), March 2005, *''The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III'', Ushio Shobō (Japan), September 1980, Book code 68343-44 *''The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition"'', Ushio Shobō (Japan), February 1988, Book code 68344-36 *''The Maru Special, Japanese Naval Vessels No.133 Japanese Submarines II "Revised edition"'', Ushio Shobō (Japan), March 1988, Book code 68344-37 *''The Maru Special, Japanese Naval Vessels No.135 Japanese Submarines IV'', Ushio Shobō (Japan), May 1988, Book code 68344-39 {{DEFAULTSORT:Ro-031 Ro-29-class submarines Kaichū type submarines Ships built by Kawasaki Heavy Industries 1923 ships 1926 ships World War II submarines of Japan Shipwrecks in the Pacific Ocean Shipwrecks of Japan Maritime incidents in August 1923 Japanese submarine accidents Maritime incidents in 1946 Scuttled vessels