L4 class
The L type submarine were medium sized submarines of the Imperial Japanese Navy, serving during the 1920s and World War II. The L type submarines were built with Vickers naval technical guidance. All boats were built in the Mitsubishi Heavy Industries-Kobe Shipyard by the contract with Vickers.
The L4 type is a license production model of the British L class submarine Group 3. Their performance was good. The IJN was satisfied with them and stopped the development of Kaichu type submarines for a long time. Later the IJN was not able to regain the technical delay in development of the medium-sized submarines until the end of the Pacific War.
Kaidai 3
The nine Kaidai IIIs were based on earlier designs, but featured a strengthened hull. The "IIIb" types were longer and had a different bow design. All nine boats were constructed between 1927 and 1930.
Of the nine Kaidai IIIs, seven survived the war, as they spent much of their time as training vessels. These were scuttled or scrapped shortly after the end of World War II. I-63 was sunk in a collision with I-60 in 1939, the former losing all her crew. I-63 was refloated and scrapped in 1940. I-60 was later sunk by HMS Jupiter.
Kaidai 4
These boats were slightly smaller than the KD3 type and with only four forward tubes, but otherwise very similar. I-162 and I-164 were originally numbered I-62 and I-64, respectively until renumbered in 1942. I-61 was lost in a collision in October 1941, refloated, and scrapped. I-162 survived the war, but I-164 was sunk by USS Triton (SS-201) in May 1942.
Kaidai 5
Three Kaidai Vs were constructed; I-165, I-166, and I-67 which were all completed in 1932. The design saw the upgrade of the deck weapon from a 50 cal to a 65 cal dual-purpose gun. The submarine was also slightly wider and taller, with an increased crew complement of 75 and an increased maximum depth of 230 ft (70 m). I-165 was modified in 1945, her gun removed and two Kaiten substituted. None of the Kaidai Vs survived World War II. I-67 was lost with all 87 crew during an exercise in 1940. I-165 was sunk on 27 June 1945, off the east coast of Saipan. I-166 was sunk by the British submarine HMS Telemachus on 17 July 1944, off the coast of Singapore.