Japanese submarine Ro-55 (1921)

The first Ro-55, originally named Submarine No. 29, was an Imperial Japanese Navy Type L submarine of the L2 subclass. Except for a few months in 1926, she was in commission from 1921 to 1938.

Design and description
The submarines of the Type L2 sub-class were close copies of the British L-class submarine built under license in Japan. They differed from the preceding L1 subclass in the deletion of the two broadside-firing torpedo tubes and the two torpedoes for them, the use of domestically produced diesel engines and batteries, and a different battery arrangement. They displaced 893 LT surfaced and 1,075.3 LT submerged. The submarines were 70.59 m long and had a beam of 7.16 m and a draft of 3.94 m. They had a diving depth of 60 m.

For surface running, the submarines were powered by two 1,200 bhp Vickers diesel engines, each driving one propeller shaft. When submerged, each propeller was driven by an 800 shp electric motor. They could reach 17.3 kn on the surface and 10.4 kn underwater. On the surface, they had a range of 5,500 nmi at 10 kn; submerged, they had a range of 80 nmi at 4 kn.

The submarines were armed with four internal 450 mm torpedo tubes, all in the bow, and carried a total of eight Type 44 torpedoes. They were also armed with a single 76.2 mm deck gun.

Construction and commissioning
Ro-55 was laid down as Submarine No. 29 on 30 March 1920 by Mitsubishi at Kobe, Japan. Launched on 10 February 1921, she was completed and commissioned on 15 November 1921.

Service history
Upon commissioning, Submarine No. 29 was attached to the Yokosuka Naval District. On 1 December 1921, she was reassigned to Submarine Division 4 in Submarine Squadron 1 in the 1st Fleet. She was renamed Ro-55 on 1 November 1924. Submarine Division 4 was reattached to the Yokosuka Naval District on 1 December 1925, and Ro-55 and was assigned that day to the Yokosuka Defense Division. She was decommissioned and placed in reserve on 1 April 1926.

Ro-55 was recommissioned on 1 August 1926, and was assigned to the Yokosuka Defense Division that day, serving in that duty until 1 December 1927. She later served in the Yokosuka Defense Division again from 30 November 1929 to 15 November 1934.

Ro-55 was decommissioned and placed in the Fourth Reserve in the Yokosuka Naval District on 15 December 1938. The Japanese struck her from the Navy list on 1 April 1940.