Japanese submarine Ro-47

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 1115 LT surfaced and 1447 LT submerged. The submarines were 80.5 m long, had a beam of 7 m and a draft of 4.07 m. They had a diving depth of 80 m.

For surface running, the boats were powered by two 2100 bhp diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600 hp electric motor. They could reach 19.75 kn on the surface and 8 kn underwater. On the surface, the K6s had a range of 11000 nmi at 12 kn; submerged, they had a range of 45 nmi at 5 kn.

The boats were armed with four internal bow 53.3 cm torpedo tubes and carried a total of ten torpedoes. They were also armed with a single 76.2 mm L/40 anti-aircraft gun and two single 25 mm AA guns.

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.

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 JAPANESE SUBMARINE I-44, JAPANESE SUBMARINE I-183, JAPANESE SUBMARINE Ro-116, and JAPANESE SUBMARINE Ro-117 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 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 yd. 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 2,500 yd. 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 9.31667°N, 136.73333°W.

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.