I.J.N. Kaidai I-class (I-51) submarine, c. 1925.

Kaidai I-class (I-51) submarine, c. 1925. Although itself not a successful design, it served as the prototype toward the development of further Kaidai-class submarines that would serve in the Pacific War, and as a platform for early submarine aircraft carrier experiments that would culminate in the development of the I-400 class submarines.

“I-51, a.k.a ‘Project S22’ and ‘Submarine No. 44’, was a submarine in commission in the Imperial Japanese Navy from 1924 to 1938. Although not a successful design, she was the lead vessel and prototype of the Japanese Kaidai-class submarines which served in World War II. The Japanese also later used her for early experiments in the development of submarine aircraft carriers.

“Following World War I, the Imperial Japanese Navy General Staff began to re-consider submarine warfare as an element of fleet strategy. Before the war, the Imperial Japanese Navy regarded submarines as useful only for short-range coastal point defense.

“However, based on the success of the Imperial German Navy in deploying long-range cruiser submarines for commerce raiding during World War I, Japanese strategists came to realize the potential for using submarines for long-range reconnaissance, as well as in a war of attrition against an enemy fleet approaching Japan. Procurement of a large, long-range Japanese submarine was authorized in fiscal year 1918 under the Eight-Eight fleet program, under the designation ‘Project S22’.

“Japanese ties to the United Kingdom via the Anglo-Japanese Alliance were still strong in the immediate aftermath of World War I, and Project S22 was based on the latest Royal Navy design, the British K-class submarine. With a displacement of 1390 tons, Project S22 was the largest submarine built in Japan up to that time … [When completed] I-51 had an unrefueled range of 20,000 nautical miles (37,000 km; 23,000 mi), which was considered remarkable for the time.

“Project S22 was laid down at the Kure Naval Arsenal in Kure, Japan, on 6 April 1921, launched on 29 November 1921, and completed on 20 June 1924, by which time she had received the name Submarine No.44. Upon completion, Submarine No. 44 was commissioned and attached to the Kure Naval District. She was renamed I-51 on 1 November 1924. I-51 remained a part of Submarine Division 17 until the division’s deactivation on 11 November 1935.

“In May 1929, I-51 began experimental work in submarine-based operation of the Yokosho 2-Go, the first prototype of the Yokosuka E6Y floatplane. She completed this testing program by September 1931. In 1931 she was fitted with an aircraft hangar which could house one floatplane which could be raised and lowered into the water by a crane, and she began testing the operation of the second E6Y prototype, the Yokosho 2-Go Kai. In 1933, an aircraft catapult was installed on her deck, making her the forerunner of the Japanese submarine aircraft carriers of World War II.

“Deactivated in 1935, I-51 was removed from the navy list in 1940, then sold and scrapped in 1941.”

– Wikipedia