Japanese submarine Ro-12
Ro-12, originally named Submarine No. 20, was an Imperial Japanese Navy "Kaichū"-Type submarine of the "Kaichū" I subclass. She and her sister ship were the first submarines built to a fully Japanese design. She was commissioned in 1919 and operated in the waters of Japan. She was stricken in 1932. Design and description. The "Kaichu"-type submarines were the first submarines built to Japanese requirements and designed specifically for service in the waters of East Asia and the Pacific Ocean. Unlike European submarines, which could lie on the bottom in the shallow waters of the North Sea and  the Mediterranean Sea, Japanese submarines needed superior depth control while operating in the deep waters of the Pacific. They also required stronger hulls than their European counterparts because of the tendency of the Pacific′s more powerful and unpredictable currents to disrupt a submerged submarine′s trim and force her below her intended operating depth. The "Kaichu" type thus were broader in beam in proportion to their length than European submarines of the period and had a greater amount of internal compartmentation and more bulkheads than was common in other submarines, resulting in more cramped and uncomfortable conditions for their crews but  a hull strength that purportedly allowed them to survive collisions, groundings, and overly deep dives that would have destroyed European submarines. In 1921, at least some naval analysts claimed that the "Kaichu" type′s hull strength gave it a greater chance of surviving a depth-charge attack than any other existing submarine class. The submarines of the "Kaichu" I subclass displaced surfaced and submerged. The submarines were long and had a beam of and a draft of . They had a diving depth of . For surface running, the submarines were powered by two Sulzer Mark II diesel engines, each driving one propeller  shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, they had a range of at ; submerged, they had a range of at . The submarines were armed with six torpedo tubes, four internal tubes in the bow and two external tubes in a trainable turret mounted on the upper deck, and carried a total of ten Type 44 torpedoes. They were also armed with a single deck gun mounted aft of the conning tower. Construction and commissioning. "Ro-12" was laid down as Submarine No. 19 on 25 April  1917 by the Kure Naval Arsenal at Kure, Japan. Launched on 1 December 1917, she was completed and commissioned on 18 September 1919. Service history. Upon commissioning, "Submarine No. 20" was attached to the Kure Naval District and was assigned to Submarine Division 14 and to the Kure Defense Division. On 1 November 1919, Submarine Division 14 was reassigned to Submarine Squadron 1 in the 1st Fleet. During maneuvers in 1919, "Submarine No. 20" collided with her sister ship "Submarine No. 19", and both submarines suffered serious damage, but they made it back to port for repairs. After commissioning, "Submarine  No. 20" began to experience chronic diesel engine problems, and during 1921 engine trouble prevented her from successfully carrying out a training cruise to Formosa. Submarine Division 14 was assigned to the Kure Defense Division and Kure Naval District on 1 July 1921, then to Submarine Squadron 2 in the 2nd Fleet on 1 December 1922. On 1 December 1923, "Submarine No. 20" was transferred to Submarine Division 3 and attached to the Yokosuka Naval District, in both of which she remained for the rest of her active career. On 1 December 1923, Submarine Division 3 was assigned to duty  in the Yokosuka Defense Division, an assignment which also continued through the end of "Submarine No. 20"′s career. She was renamed Ro-12 on 1 November 1924. "Ro-12" was stricken from the Navy list on 1 April 1932. She was renamed Haisen No. 1 that day.