Japanese Type L submarine

The submarines were medium-sized submarines of the Imperial Japanese Navy (IJN), serving during the 1920s and World War II. The "Type L" submarines were built with Vickers naval technical guidance. All boats were built in the Mitsubishi Heavy Industries-Kobe Shipyard by the contract with Vickers.
Class variants.
The "Type L" submarines were divided into four classes:
"Type L1 (Ro-51-class)".
In 1916, the Mitsubishi Shipbuilding Corporation got the Vickers "L" class submarine informations. Mitsubishi which lost competition to the Kawasaki's "Type F" submarines (Fiat-Laurenti design, "Ro-1" class and "Ro-3" class), bought the license for the "L" class submarine from Vickers. The IJN hoped an improvement of submarine technologies will be achieved and ordered this submarine from Mitsubishi. Mitsubishi bought six submarine kits, and built two boats by semi-knock down. The submarine crews were satisfied with the Vickers diesels because they proved to be reliable. The IJN studied the diesel engines and made many variants of similar design, for example: Kampon Mk.24 diesel for the ""Ro-100" class.
"Type L2 (Ro-53-class)".
The "Type L2" had minor changes from the "Type L1". The changes were:
"Type L3 (Ro-57-class)".
The "Type L3" is a license production model of the British "L" class submarine Group 2.
"Type L4 (Ro-60-class)".
The "Type L4" 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 "Kaichū" 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.