The Ro-100 class was a medium-sized, coastal submarine derived from the preceding Kaichū type. They displaced 6010NaN0 surfaced and 7820NaN0 submerged. The submarines were 60.9m (199.8feet) long, had a beam of 6m (20feet) and a draft of 3.51m (11.52feet). They had a double hull and a diving depth of 75m (246feet).[1]
For surface running, the boats were powered by two 5000NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 380hp electric motor. They could reach 14.2kn on the surface and underwater. On the surface, the Ro-100s had a range of 3500nmi at ; submerged, they had a range of 60nmi at .[2]
The boats were armed with four internal bow 53.3cm (21inches) torpedo tubes and carried a total of eight torpedoes. They were also armed with two single mounts for 250NaN0 Type 96 anti-aircraft guns or a single 76.2mm L/40 AA gun.[3]
Ro-107 was laid down as Submarine No. 217 on 17 December 1941 by the Kure Naval Arsenal at Kure, Japan.[4] Renamed Ro-107 on 8 April 1942,[4] she was launched on 17 December 1941.[4] She was completed and commissioned on 26 December 1942,[4] under the command of Lieutenant Commander Naoichi Egi.
Upon commissioning, Ro-107 was attached to the Sasebo Naval District and was assigned to the Kure Submarine Squadron for workups.[4] On 15 March 1943, she was reassigned to Submarine Squadron 7 in the 8th Fleet in the Southeast Area Fleet.[4] She departed Sasebo on 31 March 1943 bound for Rabaul on New Britain, which she reached on 12 April 1943.[4]
Ro-107 got underway from Rabaul on 22 April 1943 for her first war patrol, assigned a patrol area east of Guadalcanal in the Solomon Islands.[4] The patrol was uneventful, and she returned to Rabaul on 14 May 1943.[4] She put back to sea on 27 May 1943 to begin her second war patrol, again bound for the waters east of Guadalcanal.[4] After another quiet patrol, she set course for Rabaul, where she arrived on 20 June 1943.[4]
On 30 June 1943, the New Georgia campaign began when U.S. forces landed on New Georgia, Rendova, and other islands in the central Solomons.[4] Ro-107 left Rabaul that day to begin her third war patrol, assigned a patrol area off Rendova.[4] On 6 July 1943, she transmitted a message from a position east of Rendova.[4] The Japanese never heard from her again.[4]
The circumstances of Ro-107′s loss remain a mystery.[4] On 1 August 1943, the Imperial Japanese Navy declared her to be presumed lost in the Solomon Islands with all 42 men on board.[4] The Japanese struck her from the Navy list on 1 September 1943.[4]
Some historians have credited the United States Navy submarine chaser with sinking Ro-107 off the entrance to the harbor at Espiritu Santo in the New Hebrides in May 1943, but Ro-107 was active until July 1943.[4] Another account of her loss suggests that the U.S. Navy destroyer sank her on 7 July 1943, but Radford reported that she attacked a submarine on 1 July 1943, before Ro-107′s last message, rather than on 7 July 1943.[4] The U.S. Navy destroyer erroneously received credit for sinking a Japanese submarine in Kula Gulf on 12 July 1943 and Taylor′s victim has been widely identified by historians as Ro-107, although some historians have claimed Taylor sank .[4] Taylor′s target actually was, which survived.[4]