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]

Ro-47 was laid down as Submarine No. 388 on 28 December 1942 by Mitsui Zosensho at Tamano, Japan.^[4] She was launched on 30 August 1943, and was renamed Ro-47 that day.^[4] She was completed and commissioned on 31 January 1944.^[4]

January–May 1944 edit

Upon commissioning, Ro-47 was attached to the Maizuru Naval District.^[4] After Japanese forces sighted an Allied task force heading toward the Palau Islands, Ro-47 and the submarines I-44, I-183, Ro-116, and Ro-117 received orders on 27 March 1944 to proceed to patrol areas east of the Palaus.^[4] Ro-47 got underway from Kure, Japan, that day, called at Tokuyama to refuel from 28 to 29 March 1944,^[4] and set out for her patrol area. On 5 April 1944 she was recalled to Kure, which she reached on 13 April 1944.^[4] She was reassigned to Submarine Division 34 in the 6th Fleet on 14 May 1944.^[4]

First war patrol edit

On 13 June 1944 the Combined Fleet activated Operation A-Go for the defense of the Mariana Islands, and that day the commander-in-chief of the 6th Fleet, Vice Admiral Takeo Takagi, ordered all available Japanese submarines to deploy east of the Marianas.^[4] Accordingly, Ro-47 departed Yokosuka, Japan, to begin her first war patrol, assigned a patrol area in the Marianas off Saipan, where the Battle of Saipan began with U.S. landings on the island on 15 June 1944.^[4] In July 1944, the 6th Fleet ordered most of its submarines, including Ro-47, to withdraw from the Marianas.^[4] Ro-47 departed her patrol area on 10 July 1944 and on 16 July arrived at Maizuru, where she began repairs and an overhaul.^[4] She later moved to Kure.^[4]

Second war patrol edit

On 15 September 1944, U.S. forces invaded the Palau Islands, landing on Angaur and on Peleliu.^[4] Ro-47 got underway from Kure on 17 September 1944 with orders to attack the U.S. invasion fleet off Peleliu, assigned a patrol area south of the Palaus.^[4] On 24 September 1944, she received an order to proceed at full speed to a new patrol area in the Philippine Sea east of the Palaus.^[4] The Japanese never heard from her again.^[4]

Loss edit

The United States Navy destroyer escort USS McCoy Reynolds (DE-440) was steaming independently in the Philippine Sea northeast of the Palaus on a voyage from Peleliu to Guam when at 01:03 on 26 September 1944 she detected a vessel on the surface on radar at a range of 9,200 yards (8,400 m).^[4] When she closed with it and challenged it, it disappeared from radar, indicating a diving submarine.^[4] McCoy Reynolds then detected the submarine on sonar at a range of 2,500 yards (2,300 m).^[4] At 02:18, McCoy Reynolds launched the first of six Hedgehog barrages.^[4] After the sixth attack, the crew of McCoy Reynolds felt a large underwater explosion at 06:15 and subsequently observed oil and debris rising to the surface, marking the sinking of a Japanese submarine at 09°19′N 136°44′E / 9.317°N 136.733°E / 9.317; 136.733 (Ro-47).^[4]

The submarine McCoy Reynolds sank probably was Ro-47.^[4] On 2 November 1944, the Imperial Japanese Navy declared Ro-47 to be presumed lost off the Palau Islands with all 76 men on board.^[4] She was stricken from the Navy list on 10 March 1945.^[4]

• Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-962-6.
• Carpenter, Dorr B. & Polmar, Norman (1986). Submarines of the Imperial Japanese Navy 1904–1945. London: Conway Maritime Press. ISBN 0-85177-396-6.
• Chesneau, Roger, ed. (1980). Conway's All the World's Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN 0-85177-146-7.
• Hackett, Bob; Kingsepp, Sander (2020). "IJN Submarine RO-47: Tabular Record of Movement". SENSUIKAN! Stories and Battle Histories of the IJN's Submarines. Combinedfleet.com. Retrieved 24 September 2020.
• Hackett, Bob; Sander Kingsepp (2003). "Kaichu Type". Sensuikan!. Combinedfleet.com. Retrieved 20 September 2020.
• Hashimoto, Mochitsura (1954). Sunk: The Story of the Japanese Submarine Fleet 1942 – 1945. Colegrave, E.H.M. (translator). London: Cassell and Company. ASIN B000QSM3L0.