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.
Imperial Russian Navy
Due to the ongoing blockade of Port Arthur in 1904, the Imperial Russian Navy dispatched their remaining submarines to Vladivostok, and by the end of 1904 the last of seven subs had reached their new base there. Using the seven boats as a foundation, the Imperial Russian Navy created the world's first operational submarine fleet at Vladivostok on 1 January 1905. On 14 February 1905 the new "submarine fleet" sent out its first combat patrol consisting of the vessels "Som" and "Delfin". With patrols varying from 24 hours to a few days, the sub fleets first enemy contact occurred on 29 April 1905 when Imperial Japanese Navy torpedo boats fired upon "Som", withdrawing after failing to score a hit. On 1 July the Russian submarine "Keta" made contact with two Japanese torpedo boats in the Tartar Strait. "Keta" could not submerge quick enough to obtain a firing position and both adversaries broke contact.