Ro-47 was an Imperial Japanese Navy Kaichū type submarine of the K6 sub-class. Completed and commissioned in January 1944, she served in World War II in operations related to the Mariana and Palau Islands campaign. She was sunk in September 1944 during her second war patrol.

Design and description The submarines of the K6 sub-class were versions of the preceding K5 sub-class with greater range and diving depth. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a diving depth of .Bagnasco, p. 187

For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor.Chesneau, p. 203 They could reach on the surface and underwater. On the surface, the K6s had a range of at ; submerged, they had a range of at .

The boats were armed with four internal bow torpedo tubes and carried a total of ten torpedoes. They were also armed with a single L/40 anti-aircraft gun and two single AA guns.Carpenter & Dorr, p. 124

Construction and commissioning

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

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

First war patrol

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. 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. In July 1944, the 6th Fleet ordered most of its submarines, including Ro-47, to withdraw from the Marianas. Ro-47 departed her patrol area on 10 July 1944 and on 16 July arrived at Maizuru, where she began repairs and an overhaul. She later moved to Kure.

Second war patrol

On 15 September 1944, U.S. forces invaded the Palau Islands, landing on Angaur and on Peleliu. 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. 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. The Japanese never heard from her again.

Loss

The United States Navy destroyer escort 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 . When she closed with it and challenged it, it disappeared from radar, indicating a diving submarine. McCoy Reynolds then detected the submarine on sonar at a range of . At 02:18, McCoy Reynolds launched the first of six Hedgehog barrages. 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 .

The submarine McCoy Reynolds sank probably was Ro-47. 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. She was stricken from the Navy list on 10 March 1945.

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