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]
Upon commissioning, Ro-42 was attached formally to the Maizuru Naval District and assigned to Submarine Squadron 11 for workups.[4] On 30 November 1943, she was reassigned to Submarine Division 34 in the 6th Fleet,[4] and on 4 December 1943 she departed Maizuru, Japan, bound for Truk, which she reached on 12 December 1943.[4]
During Ro-42′s stay at Truk, U.S. Navy Task Force 58 conducted Operation Hailstone, a major attack on Truk by carrier aircraft supported by anti-shipping sweeps around the atoll by surface warships, on 17 and 18 February 1944.[4]Ro-42 and the submarines I-10 and Ro-36 put to sea on 17 February in an attempt to intercept the attacking ships.[4]Ro-42 was unsuccessful, and returned to Truk on 19 February 1944.[4]
Second war patrol
Ro-42 began her second war patrol on 25 February 1944, departing Truk to head for a patrol area east of Kusaie.[4] On 1 March she received orders to conduct a reconnaissance of Kwajalein and then move to a new patrol area 120 nautical miles (220 km; 140 mi) southeast of Kwajalein.[4] After she arrived off Kwajalein, she reported on 4 March 1944 that the island′s waters were too heavily patrolled by Alliedpatrol boats for her to approach it for a reconnaissance.[4]Ro-42 also began to suffer from malfunctioning equipment.[4] She was ordered to return to her patrol.[4]
Ro-42 was 40 nautical miles (74 km; 46 mi) southwest of Mili Atoll in the Marshall Islands when she sighted a convoy of six transports at 08:00 on 6 March 1944.[4] WHile 70 nautical miles (130 km; 81 mi) southwest of Mili on 15 March 1944, she reported sighting a battleship and five aircraft carriers of U.S. Navy Task Group 50.10, prompting the commander-in-chief of the 6th Fleet, Vice AdmiralTakeo Takagi, to order the submarines Ro-36 and Ro-44 to intercept the ships.[4]
On 16 March 1944, Ro-42 received orders to move 100 nautical miles (190 km; 120 mi) to the west-southwest,[4] and on 18 March to move another 80 nautical miles (150 km; 92 mi) to the west.[4] She was 240 nautical miles (440 km; 280 mi) south of Ponape on 21 March 1944 when she sighted a three-ship convoy.[4] On 23 March 1944, she and the submarines I-16, Ro-36, Ro-41, Ro-43, Ro-44, and Ro-108 were ordered to intercept a U.S. Navy task force that the submarine I-32 had sighted 60 nautical miles (110 km; 69 mi) north of Jaluit Atoll that day.[4] She did not find the task force, and she returned to Truk on 28 March 1944.[4]
April–May 1944
Ro-42 got underway from Truk in company with the submarines I-174, Ro-36, Ro-48, and Ro-108 on 12 April 1944 to intercept an Allied task force Japanese forces had sighted north of Kavieng.[4] She returned to Truk on 14 April.[4] On 23 April 1944 she departed Truk bound for Yokosuka, Japan, which she reached on 30 April 1944.[4]
On 15 May 1944, Ro-42 departed Yokosuka with the commander of Submarine Division 34 embarked and orders to conduct a reconnaissance of the American fleet anchorage at Majuro and then proceed to an area north-northeast of Kwajalein.[4] While she was at sea, she received orders to postpone the Majuro reconnaissance until 10 June 1944.[4] On 10 June 1944, she was operating in the Marshall Islands when she was ordered to reconnoiter both Majuro and Kwajalein.[4]
Loss
Ro-42 was on the surface 40 nautical miles (74 km; 46 mi) east of Roi-Namur at 23:30 on 10 June 1944 when the destroyer escortUSS Bangust (DE-739) detected her on radar.[4] After Bangust closed, made visual contact, and flashed a challenge, Ro-42 crash-dived.[4]Bangust searched for the submerged Ro-42 for the next eight hours and regained contact on sonar on the morning of 11 June 1944.[4]Bangust conducted three unsuccessful 24-projectile Hedgehog attacks as Ro-42 made evasive maneuvers such as frequent hard turns and sudden changes in speed.[4] However, her fourth Hedgehog attack resulted in a large underwater explosion that damaged Bangust′s hull.[4]Ro-42 tried to surface, but failed, and sank at 10°05′N168°22′E / 10.083°N 168.367°E / 10.083; 168.367 (Ro-42).[4] During the morning of 11 June, a large oil slick was sighted on the surface.[4]
On 13 June 1944 the Combined Fleet activated Operation A-Go for the defense of the Mariana Islands, and that day Vice Admiral Takagi ordered all available Japanese submarines to deploy east of the Marianas,[4] with Ro-42 ordered to head there at flank speed.[4] On 16 June 1944, she was assigned to Submarine Group B and ordered to move to an area southeast of the Marianas,[4] and on 22 June 1944 she was ordered to return to Truk.[4] She acknowledged none of the orders. On 12 July 1944, the Imperial Japanese Navy declared Ro-42 to be presumed lost with all 73 hands.[4] She was stricken from the Navy list on 10 August 1944.[4]
Some historians have identified a Japanese submarine the U.S. submarine USS Sea Devil (SS-400) sank on 16 September 1944 east of Japan as Ro-42, but the submarine Sea Devil sank probably was I-364.[4]
Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis, Maryland: Naval Institute Press. ISBN0-87021-962-6.
Carpenter, Dorr B. & Polmar, Norman (1986). Submarines of the Imperial Japanese Navy 1904–1945. London: Conway Maritime Press. ISBN0-85177-396-6.
Chesneau, Roger, ed. (1980). Conway's All the World's Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN0-85177-146-7.
Hackett, Bob; Kingsepp, Sander (2017). "IJN Submarine RO-42: Tabular Record of Movement". SENSUIKAN! Stories and Battle Histories of the IJN's Submarines. Combinedfleet.com. Retrieved 22 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.
