The was a class of submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 in the Imperial Japanese Navy

Imperial Japanese Navy

The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...

 (IJN), serving from the 1920s to the Second World War. The IJN classed it as a .

Construction

The Empire of Japan

Empire of Japan

The Empire of Japan is the name of the state of Japan that existed from the Meiji Restoration on 3 January 1868 to the enactment of the post-World War II Constitution of...

 received six U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

s as a reparation payment after World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. The IJN copied and designed the I-21 class (later renamed I-121 class) minelaying submarine. Six boats were ordered, of which four were completed, two were cancelled. All boats were built in the Kawasaki Yard

Kawasaki Shipbuilding Corporation

-External links:*...

 at Kobe.

Service

When Word War II began, they were considered obsolete and used as minelayers and supply submarines for flying boats in the Pacific

Pacific War

The Pacific War, also sometimes called the Asia-Pacific War refers broadly to the parts of World War II that took place in the Pacific Ocean, its islands, and in East Asia, then called the Far East...

. Three boats of the class were lost in action. The I-121 survived the war and was sunk as a target post war.

Boats in class

Name	Laid down	Launched	Completed	Successes	Fate
I-21 I-121	20 October 1924	30 March 1926	31 March 1927	Sank Dutch merchant ship Bantam on 18 January 1942	Renamed I-121 on 1 June 1938. Decommissioned on 30 November 1945. Sunk as a target off Maizuru Maizuru, Kyoto is a city located in Kyōto, Japan, on an inlet of the Sea of Japan.As of 2008, the city has an estimated population of 89,626 and the density of 264 persons per km². The total area is .The city was founded on May 27, 1943....  on 30 April 1946 by the United States Navy United States Navy The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S... .
I-22 I-122	28 February 1925	8 November 1926	28 October 1927		Renamed I-122 on 1 June 1938. Sunk by USS Skate USS Skate (SS-305) USS Skate was a United States Navy Balao-class submarine named for the skate, a type of ray.Skate was laid down at the Mare Island Naval Shipyard of Vallejo, California, 1 August 1942. She was launched on 4 March 1943, sponsored by Mrs. George P. Shamer and commissioned on 15 April with Commander...  at Noto Peninsula Noto Peninsula thumb|right|240px|Landsat image with high-resolution data from Space Shuttle.Noto Peninsula is a peninsula that projects north into the Sea of Japan from the coast of Ishikawa prefecture in central Honshū, the main island of Japan...  37°29′N 137°25′E on 9 June 1945.
I-23 I-123	12 June 1925	19 March 1927	28 April 1928		Renamed I-123 on 1 June 1938. Sunk by USS Gamble USS Gamble (DD-123) USS Gamble was a Wickes class destroyer in the United States Navy during World War I, later converted to a minelayer in World War II. She was named for two brothers, Lieutenant Peter Gamble and Lieutenant Colonel John M...  at Indispensable Strait Indispensable Strait Indispensable Strait is a waterway in the Solomon Islands, running about 200 km northwest-southeast from Santa Isabel to Makira , between the Florida Islands and Guadalcanal to the southwest, and Malaita to the northeast....  on 29 August 1942.
I-24 I-124	17 April 1926	12 December 1927	10 December 1928	Sank RMS Hareldawins on 10 December 1941	Renamed I-124 on 1 June 1938. Sunk by HMAS Deloraine HMAS Deloraine HMAS Deloraine , named for the town of Deloraine, Tasmania, was one of 60 Bathurst class corvettes constructed during World War II, and one of 36 initially manned and commissioned solely by the Royal Australian Navy .-Construction:... , HMAS Katoomba HMAS Katoomba HMAS Katoomba , named for the tourist resort of Katoomba, New South Wales, was one of 60 Bathurst class corvettes constructed during World War II, and one of 36 initially manned and commissioned solely by the Royal Australian Navy ....  and HMAS Lithgow at Port Darwin Darwin, Northern Territory Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 127,500, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities... 12°05′N 130°06′E on 20 January 1942.
2 boats					Cancelled in 1924.

External links

• Submarine I-121: Tabular Record of Movement