The submarines of the Kaichu V sub-class were designed for anti-shipping operations and carried more fuel and had greater range and a heavier gun armament than preceding Kaichu-type submarines. They displaced 866 tonnes (852 long tons) surfaced and 1,036 tonnes (1,020 long tons) submerged. The submarines were 74.22 meters (243 ft 6 in) long and had a beam of 6.12 meters (20 ft 1 in) and a draft of 3.73 meters (12 ft 3 in). They had a diving depth of 45.7 meters (150 ft).
For surface running, the submarines were powered by two 600-brake-horsepower (447 kW) Sulzerdiesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600-horsepower (447 kW) electric motor. They could reach 13 knots (24 km/h; 15 mph) on the surface and 8.5 knots (15.7 km/h; 9.8 mph) underwater. On the surface, they had a range of 9,000 nautical miles (17,000 km; 10,000 mi) — although the Imperial Japanese Navy officially announced it as 6,000 nautical miles (11,000 km; 6,900 mi) — at 10 knots (19 km/h; 12 mph); submerged, they had a range of 85 nmi (157 km; 98 mi) at 4 knots (7.4 km/h; 4.6 mph).
The submarines were armed with four internal bow 533 mm (21.0 in) torpedo tubes and carried a total of eight torpedoes. They were also armed with a single 120 mm (4.7 in) deck gun and one 6.5 mmmachine gun.
Upon commissioning, Submarine No. 71 was attached to the Sasebo Naval District, to which she remained attached throughout her active career.[1] On 15 June 1924, she was assigned to both Submarine Division 25 — in which she spent her active career — and the Mako Defense Division headquartered at Mako in the Pescadores Islands.[1] She was renamed Ro-32 on 1 November 1924.[1] On 1 December 1926, she was reassigned to the Sasebo Defense Division, headquartered at Sasebo, Japan.[1] Her service in the Sasebo Defense Division ended on 15 November 1934, after which she served as a unit of Submarine Division 25 in the Sasebo Naval District.[1]
Ro-32 was decommissioned and placed in the Fourth Reserve on 15 December 1938.[1] The Japanese struck her from the Navy list on 1 April 1942,[1] and that day she became a stationary traininghulk at the submarine school at Ōtake, Japan.[1] She was scrapped ca. August 1945.[1]
^The identity of the submarine reportedly sunk on 9 July 1942 remains undetermined. One hypothesis is that she was the Soviet Navy submarine Shch-138, which the Soviet Navy reported missing on 10 July 1942, the day following the sinking. The Soviet Union later claimed that Shch-138 sank in the harbor at Nikolayevsk-on-Amur on the Amur River in the Soviet Union on 18 July 1942 after the explosion of four of her torpedoes, was refloated immediately, sank again the following the day during a storm while under tow, and finally was refloated a second time on 11 July 1943 and scrapped. A photo of the submarine reportedly taken by the crew of the Bolingbroke involved in her sinking purportedly shows a gray submarine — submarines of the Soviet Pacific Ocean Fleet were painted gray during World War II, while Japanese submarines were black — and the number "8" among characters painted on her conning tower, consistent with the markings on Shch-138′s conning tower. Some researchers have suggested that the Soviet narrative of Shch-138′s loss at Nikolayevsk-on-Amur may be intended to cover up Shch-138′s loss while clandestinely collecting information along the coast of the United States and Canada. (See Bruhn, p. 128.)
Rekishi Gunzō, History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005, ISBN4-05-603890-2
The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III, Ushio Shobō (Japan), September 1980, Book code 68343-44
The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition", Ushio Shobō (Japan), February 1988, Book code 68344-36
The Maru Special, Japanese Naval Vessels No.133 Japanese Submarines II "Revised edition", Ushio Shobō (Japan), March 1988, Book code 68344-37
The Maru Special, Japanese Naval Vessels No.135 Japanese Submarines IV, Ushio Shobō (Japan), May 1988, Book code 68344-39
Bruhn, David D. Battle Stars for the "Cactus Navy": America's Fishing Vessels and Yachts in World War II. Berwyn Heights, Maryland: Heritage Books 2014. ISBN978-0-7884-5573-5
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