Japanese submarine I-51
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 Japanese Navy regarded submarines as useful only for short-range coastal point defense. However, based on the success of the Imperial German Navy in deployment of long-range cruiser-submarines for commerce raiding Japanese strategists came to realize possibilities for using the weapon for long range reconnaissance, and in a war of attrition against an enemy fleet approaching Japan. Procurement for a large, long-range Japanese submarine was authorized in fiscal 1918 under the Eight-six fleet program, under the designation S22.
"Project S22" was based on the latest Royal Navy design, the British K class submarine. Japanese ties to Great Britain via the Anglo-Japanese Alliance were still strong. "Project S22" was laid down at Kure Naval Arsenal on 6 April 1921, launched on 29 November 1921 and completed on 20 June 1924.
Japanese submarine tender Karasaki
At the end of 1904, "Karasaki Maru" was sent to the Yokosuka Naval Arsenal for conversion into a submarine tender. She was officially commissioned into the Imperial Japanese Navy on 4 July 1905. On 8 March 1906, she was renamed "Karasaki", and was officially re-designated as a torpedo boat tender. In August 1912, the Imperial Japanese Navy abolished the torpedo boat tender classification, and "Karasaki" was re-designated as a second-class "kaibokan". However, the designation of torpedo boat tender was revived in April 1920. From 1924, "Karasaki" was then assigned to the submarine training school at Kure Naval District, and from 1 December 1924, was again officially designated as a submarine tender.