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.
HA. 19 (Japanese Midget Submarine)
The HA. 19 (also known as Japanese Midget Submarine "C" by the US Navy) is a historic Imperial Japanese Navy midget submarine that was part of the Japanese attack on Pearl Harbor on 7 December 1941. This submarine was ordered to enter Pearl Harbor then attack the American warships with its torpedoes and then be scuttled with explosives next to a warship. However, she did not enter the harbor, and was grounded and captured. The submarine was eventually put on display near the submarine squadron at Naval Station Key West, Florida, then moved to the nearby Key West Lighthouse and Military Museum. "HA. 19" is now displayed at the National Museum of the Pacific War in Fredericksburg, Texas.