Japanese submarine Ro-56 (1944)
Kaichū-type submarine
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The second Ro-56 was an Imperial Japanese Navy Kaichū type submarine of the K6 sub-class. Completed and commissioned in November 1944, she served in World War II and was sunk during her first war patrol in April 1945.
| History | |
|---|---|
 Japan | |
| Name | Ro-75 |
| Builder | Mitsui Zosensho, Tamano, Japan |
| Laid down | 2 December 1943 |
| Renamed | Ro-56 |
| Launched | 5 July 1944 |
| Completed | 15 November 1944 |
| Commissioned | 15 November 1944 |
| Fate | Sunk 9 April 1945 |
| Stricken | 25 May 1945 |
| General characteristics | |
| Class & type | Kaichū type submarine (K6 subclass) |
| Displacement |
|
| Length | 80.5 m (264 ft 1 in) overall |
| Beam | 7 m (23 ft 0 in) |
| Draft | 4.07 m (13 ft 4 in) |
| Installed power |
|
| Propulsion |
|
| Speed |
|
| Range |
|
| Test depth | 80 m (260 ft) |
| Crew | 61 |
| Armament |
|
Design and description
The submarines of the K6 sub-class were versions of the preceding K5 sub-class with greater range and diving depth.[1] They displaced 1,133 tonnes (1,115 long tons) surfaced and 1,470 tonnes (1,447 long tons) submerged. The submarines were 80.5 meters (264 ft 1 in) long, had a beam of 7 meters (23 ft 0 in) and a draft of 4.07 meters (13 ft 4 in). They had a diving depth of 80 meters (260 ft).[2]
For surface running, the boats were powered by two 2,100-brake-horsepower (1,566 kW) diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600-horsepower (447 kW) electric motor.[3] They could reach 19.75 knots (36.58 km/h; 22.73 mph) on the surface and 8 knots (15 km/h; 9.2 mph) underwater. On the surface, the K6s had a range of 11,000 nautical miles (20,000 km; 13,000 mi) at 12 knots (22 km/h; 14 mph); submerged, they had a range of 45 nmi (83 km; 52 mi) at 5 knots (9.3 km/h; 5.8 mph).[1]
The boats were armed with four internal bow 53.3 cm (21.0 in) torpedo tubes and carried a total of ten torpedoes. They were also armed with a single 76.2 mm (3.00 in) L/40 anti-aircraft gun and two single 25 mm (1.0 in) AA guns.[1]
Construction and commissioning
Submarine No. 645 was laid down on 2 December 1943 by Mitsui Zosensho at Tamano, Japan, with the provisional name Ro-75.[4] She had been renamed Ro-56 — the second submarine of that name — by the time she was launched on 5 July 1944.[4] She was completed and commissioned on 15 November 1944.[4]
Service history
Upon commissioning, Ro-56 was attached to the Maizuru Naval District and assigned to Submarine Squadron 11 for workups.[4] She was reassigned to Submarine Division 34 in the 6th Fleet on 10 February 1945.[4] She arrived at Saeki, Japan, on 16 March 1945.[4]
First war patrol
On 18 March 1945, Ro-56 departed Saeki to begin her first war patrol, ordered to operate southwest of Kyushu along with the submarines I-8, Ro-41, and Ro-49.[4] She reported on 22 March 1945 that she had reached her patrol area.[4] While she was at sea, the Battle of Okinawa began with the U.S. landings on Okinawa on 1 April 1945.[4]
Loss
On 9 April 1945, the United States Navy destroyers USS Monssen (DD-798) and USS Mertz (DD-691) were escorting the aircraft carriers of Task Force 58 45 nautical miles (83 km; 52 mi) west of Okinawa when Monssen detected a submerged submarine on sonar at a range of 900 yards (820 m).[4] Monssen dropped three patterns of depth charges, after which Mertz joined the attack and dropped another three patterns.[4] Monssen then made two more depth-charge attacks, sinking the submarine at 26°09′N 130°21′E.[4]
The submarine Monssen and Mertz sank probably was Ro-56.[4] On 15 April 1945, the Imperial Japanese Navy declared her to be presumed lost off Okinawa with all 79 men on board.[4] The Japanese struck her from the Navy list on 25 May 1945.[4]
Some accounts claim that the U.S. submarine USS Sea Owl (SS-405) sank Ro-56 northeast of Wake Island on 18 April 1945,[4] but Ro-56 never operated near Wake. The submarine Sea Owl attacked was I-372 — and I-372 survived the attack.[4]