Japanese submarine Ro-25

Ro-25, originally named Submarine No. 43, was an Imperial Japanese Navy Kaichū-Type submarine of the Kaichū III subclass. She was commissioned in 1921 and operated in the waters of Japan and Formosa. She sank after a collision in 1924, and after salvage and repairs returned to service from 1925 to 1936.

History
Japan
Name: Submarine No. 43
Builder: Sasebo Naval Arsenal, Sasebo, Japan
Laid down: 19 February 1920
Launched: 17 July 1920
Completed: 25 October 1921
Commissioned: 25 October 1921
Renamed: Ro-25 on 1 November 1924
Decommissioned: 26 April 1924
Recommissioned: 4 May 1925
Stricken: 1 April 1936
Fate: Scrapped 1936
General characteristics
Class and type: Kaichū type submarine (K3 subclass)
Displacement:
  • 752 tonnes (740 long tons) surfaced
  • 1,013 tonnes (997 long tons) submerged
Length: 70.10 m (230 ft 0 in) overall
Beam: 6.12 m (20 ft 1 in)
Draft: 3.70 m (12 ft 2 in)
Installed power:
Propulsion:
Speed:
  • 16.5 knots (30.6 km/h; 19.0 mph) surfaced
  • 8.5 knots (15.7 km/h; 9.8 mph) submerged
Range:
  • 6,000 nmi (11,000 km; 6,900 mi) at 10 knots (19 km/h; 12 mph) surfaced
  • 85 nmi (157 km; 98 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth: 45.7 m (150 ft)
Crew: 46
Armament:

Design and description

The submarines of the Kaichu III sub-class were a slightly improved version of the preceding Kaichu II subclass, the man difference being an increase in diving depth from 30 to 45.7 meters (98 to 150 ft).[1] They displaced 752 tonnes (740 long tons) surfaced and 1,013 tonnes (997 long tons) submerged. The submarines were 70.10 meters (230 ft 0 in) long and had a beam of 6.12 meters (20 ft 1 in) and a draft of 3.70 meters (12 ft 2 in).

For surface running, the submarines were powered by two 1,450-brake-horsepower (1,081 kW) Sulzer Mark II diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600-horsepower (447 kW) electric motor. They could reach 16.5 knots (31 km/h; 19 mph) on the surface and 8.5 knots (15.7 km/h; 9.8 mph) underwater. On the surface, they had a range of 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 six 450 mm (18 in) torpedo tubes, four internal tubes in the bow and two external tubes mounted on the upper deck, and carried a total of ten Type 44 torpedoes. They were also armed with a single 76.2 mm (3.00 in) deck gun mounted aft of the conning tower.[1]

Construction and commissioning

Ro-25 was laid down as Submarine No. 43 on 19 February 1920 by the Sasebo Naval Arsenal at Sasebo, Japan.[2] Launched on 17 July 1920,[2] she was completed and commissioned on 25 October 1921.[2]

Service history

Upon commissioning, Submarine No. 43 was attached to the Sasebo Naval District, to which she remained attached throughout her career.[2] On 15 December 1921, she was assigned to Submarine Division 22 and to the Mako Defense Division at Mako off Formosa.[2] On 1 December 1922, Submarine Division 22 was reassigned to the Sasebo Defense Division.[2]

On 19 March 1924, Submarine No. 43 was taking part in maneuvers off the harbor at Sasebo when she collided with the light cruiser Tatsuta.[3][4][5] Tatsuta sliced through Submarine No. 43′s conning tower,[5] and Submarine No. 43 sank 3 nautical miles (5.6 km; 3.5 mi) off Sasebo in 156 feet (48 m) of water.[3] Using a telephone floated from the sunken submarine, a rescue party on the surface established contact with the crewmen trapped aboard her, who reported ever-deteriorating conditions[3] before falling silent about ten hours after she sank.[5] Submarine No. 43′s entire crew of 46 suffocated.[3]

Submarine No. 43 was partially raised and towed to Sasebo, where she arrived on 13 April 1924 so that salvage operations could be completed in the protected waters of the harbor.[4] She was fully refloated on 25 April 1924[2] and on 26 April was decommissioned and placed in reserve in the Sasebo Naval District to undergo repairs.[2] While under repair, she was renamed Ro-25 on 1 November 1924.[2] Her repairs were completed on 4 May 1925,[2] and on 1 March 1926 she was recommissioned and returned to service in both Submarine Division 22 and the Sasebo Defense Division.[2] On 1 December 1927 she was reassigned directly to the Sasebo Naval District[2] and subsequently was used for trials.[1]

Ro-25 was stricken from the Navy list on 1 April 1936.[2] She subsequently was scrapped during 1936.[2]

Commemoration

The Submarine No. 43 Memorial, a gray obelisk commemorating the 1924 sinking of Submarine No. 43, stands on Udogoe, overlooking Sasebo.[5] It provides a vantage point from which visitors can see the area in which she sank.[5]

Notes
  1. Gray, Randal, ed., Conway′s All the World′s Fighting Ships 1906–1921, Annapolis, Maryland: Naval Institute Press, 1985, ISBN 0 87021 907 3, p. 248.
  2. "RO-25 ex No-43". iijnsubsite.info. 2018. Retrieved 14 October 2020.
  3. "Submarine Accidents Involving Loss of Life Since World War," Navy Appropriation Bill for 1929, Seventieth Congress of the United States, Washington, D.C.: Government Printing Office, 1928, p. 107.
  4. Anonymous, "Sunken Submarine Towed Into Harbour," Reuters, 13 April 1924
  5. Krigbaum, David, "Picnic among the Pits: Tajimadake Naval Guard Station and Submarine No. 43 Memorial," Wayfarer Daves Travel and History, December 11, 2017 Accessed 14 October 2020.

References
  • "Rekishi Gunzō"., History of Pacific War Vol.17 I-Gō Submarines, Gakken (Japan), January 1998, ISBN 4-05-601767-0
  • Rekishi Gunzō, History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005, ISBN 4-05-603890-2
  • 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
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