Japanese submarine Ro-42

The submarines of the K6 sub-class were versions of the preceding K5 sub-class with greater range and diving depth. They displaced {{Convert|1115|LT|t|0|disp=flip}} surfaced and {{Convert|1447|LT|t|0|disp=flip}} submerged. The submarines were {{convert|80.5|m|ftin|sp=us}} long, had a beam of {{convert|7|m|ftin|sp=us}} and a draft of {{convert|4.07|m|ftin|sp=us}}. They had a diving depth of {{convert|80|m|ft|sp=us}}.Bagnasco, p. 187

For surface running, the boats were powered by two {{convert|2100|bhp|lk=in|0|adj=on}} diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a {{convert|600|hp|0|adj=on}} electric motor.Chesneau, p. 203 They could reach {{convert|19.75|kn|lk=in}} on the surface and {{convert|8|kn}} underwater. On the surface, the K6s had a range of {{convert|11000|nmi|lk=in}} at {{convert|12|kn}}; submerged, they had a range of {{convert|45|nmi|abbr=on}} at {{convert|5|kn}}.

The boats were armed with four internal bow {{convert|53.3|cm|in|1|abbr=on|sp=us}} torpedo tubes and carried a total of ten torpedoes. They were also armed with a single 8 cm/40 3rd Year Type naval gun L/40 anti-aircraft gun and two single Type 96 25 mm AT/AA Gun.Carpenter & Dorr, p. 124

Ro-42 was laid down as Submarine No. 208 on 27 April 1942 by the Sasebo Navy Yard at Sasebo, Japan.{{cite web |url= http://www.combinedfleet.com/RO-42.htm |title=IJN Submarine RO-42: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=22 September 2020}} She was renamed Ro-42 on 25 September 1942 and was attached provisionally to the Maizuru Naval District that day. She was launched on 25 October 1942 and was completed and commissioned on 31 August 1943.

Upon commissioning, Ro-42 was attached formally to the Maizuru Naval District and assigned to Submarine Squadron 11 for workups. On 30 November 1943, she was reassigned to Submarine Division 34 in the 6th Fleet, and on 4 December 1943 she departed Maizuru, Japan, bound for Truk, which she reached on 12 December 1943.

Ro-40 got underway from Truk on 23 December 1943 to begin her first war patrol, assigned a patrol area off Espiritu Santo in the New Hebrides. She was {{convert|200|nmi}} east of Espiritu Santo on 14 January 1944 when she torpedoed the 800-ton United States Navy fuel oil barge {{USS|YO-159}}, which her commanding officer had mistaken for a 10,000-ton fleet oiler, at {{coord|15|27|S|171|28|E|name=USS YO-159}}. YO-159 suffered such serious damage that U.S. forces later scuttled her. Ro-42 returned to Truk on 24 January 1944. She took aboard torpedoes from the auxiliary submarine tender {{ship||Heian Maru|1930|2}} there on 28 January 1944.

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. Ro-42 and the submarines {{ship|Japanese submarine|I-10||2}} and {{ship|Japanese submarine|Ro-36||2}} put to sea on 17 February in an attempt to intercept the attacking ships. Ro-42 was unsuccessful, and returned to Truk on 19 February 1944.

Ro-42 began her second war patrol on 25 February 1944, departing Truk to head for a patrol area east of Kusaie. On 1 March she received orders to conduct a reconnaissance of Kwajalein and then move to a new patrol area {{convert|120|nmi}} southeast of Kwajalein. After she arrived off Kwajalein, she reported on 4 March 1944 that the island′s waters were too heavily patrolled by Allied patrol boats for her to approach it for a reconnaissance. Ro-42 also began to suffer from malfunctioning equipment. She was ordered to return to her patrol.

Ro-42 was {{convert|40|nmi}} southwest of Mili Atoll in the Marshall Islands when she sighted a convoy of six transports at 08:00 on 6 March 1944. WHile {{convert|70|nmi}} 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 Admiral Takeo Takagi, to order the submarines Ro-36 and {{ship|Japanese submarine|Ro-44||2}} to intercept the ships.

On 16 March 1944, Ro-42 received orders to move {{convert|100|nmi}} to the west-southwest, and on 18 March to move another {{convert|80|nmi}} to the west. She was {{convert|240|nmi}} south of Ponape on 21 March 1944 when she sighted a three-ship convoy. On 23 March 1944, she and the submarines {{ship|Japanese submarine|I-16||2}}, Ro-36, {{ship|Japanese submarine|Ro-41||2}}, {{ship|Japanese submarine|Ro-43||2}}, {{ship|Japanese submarine|Ro-44||2}}, and {{ship|Japanese submarine|Ro-108||2}} were ordered to intercept a U.S. Navy task force that the submarine {{ship|Japanese submarine|I-32||2}} had sighted {{convert|60|nmi}} north of Jaluit Atoll that day. She did not find the task force, and she returned to Truk on 28 March 1944.

Ro-42 got underway from Truk in company with the submarines {{ship|Japanese submarine|I-174||2}}, Ro-36, {{ship|Japanese submarine|Ro-48||2}}, and {{ship|Japanese submarine|Ro-108||2}} on 12 April 1944 to intercept an Allied task force Japanese forces had sighted north of Kavieng. She returned to Truk on 14 April. On 23 April 1944 she departed Truk bound for Yokosuka, Japan, which she reached on 30 April 1944.

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. While she was at sea, she received orders to postpone the Majuro reconnaissance until 10 June 1944. On 10 June 1944, she was operating in the Marshall Islands when she was ordered to reconnoiter both Majuro and Kwajalein.

Ro-42 was on the surface {{convert|40|nmi}} east of Roi-Namur at 23:30 on 10 June 1944 when the destroyer escort {{USS|Bangust|DE-739}} detected her on radar. After Bangust closed, made visual contact, and flashed a challenge, Ro-42 crash-dived. Bangust searched for the submerged Ro-42 for the next eight hours and regained contact on sonar on the morning of 11 June 1944. Bangust conducted three unsuccessful 24-projectile Hedgehog attacks as Ro-42 made evasive maneuvers such as frequent hard turns and sudden changes in speed. However, her fourth Hedgehog attack resulted in a large underwater explosion that damaged Bangust′s hull. Ro-42 tried to surface, but failed, and sank at {{coord|10|05|N|168|22|E|name=Ro-42}}. During the morning of 11 June, a large oil slick was sighted on the surface.

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, with Ro-42 ordered to head there at flank speed. On 16 June 1944, she was assigned to Submarine Group B and ordered to move to an area southeast of the Marianas, and on 22 June 1944 she was ordered to return to Truk. 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. She was stricken from the Navy list on 10 August 1944.

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 {{ship|Japanese submarine|I-364||2}}.

{{Reflist|30em}}

• {{cite book|last=Bagnasco |first=Erminio |title=Submarines of World War Two |year=1977 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=0-87021-962-6}}
• {{cite book|last1=Carpenter|first1=Dorr B.|last2=Polmar|first2=Norman|title=Submarines of the Imperial Japanese Navy 1904–1945|year=1986|publisher=Conway Maritime Press|location=London|isbn=0-85177-396-6|name-list-style=amp}}
• {{cite book|title=Conway's All the World's Fighting Ships 1922–1946|editor1-last=Chesneau|editor1-first=Roger|publisher=Conway Maritime Press|location=Greenwich, UK|year=1980|isbn=0-85177-146-7}}
• {{cite web|url=http://www.combinedfleet.com/RO-42.htm|title=IJN Submarine RO-42: Tabular Record of Movement|last1=Hackett|first1=Bob|last2=Kingsepp|first2=Sander|year=2017|work=SENSUIKAN! Stories and Battle Histories of the IJN's Submarines|publisher=Combinedfleet.com|access-date=22 September 2020}}
• {{cite web|url=http://www.combinedfleet.com/type_kaichu.htm|title=Kaichu Type|last=Hackett|first=Bob |author2=Sander Kingsepp |year=2003|work=Sensuikan!|publisher=Combinedfleet.com|access-date=20 September 2020}}
• {{cite book|last=Hashimoto|first=Mochitsura|others=Colegrave, E.H.M. (translator)|title=Sunk: The Story of the Japanese Submarine Fleet 1942 – 1945|publisher=Cassell and Company|location=London|year=1954|id=ASIN B000QSM3L0}}

{{Kaichū type submarine}}

{{June 1944 shipwrecks}}

{{DEFAULTSORT:Ro-042}}

Category:Ro-35-class submarines

Category:Kaichū type submarines

Category:Ships built by Sasebo Naval Arsenal

Category:1942 ships

Category:World War II submarines of Japan

Category:Japanese submarines lost during World War II

Category:World War II shipwrecks in the Pacific Ocean

Category:Maritime incidents in June 1944

Category:Warships lost in combat with all hands

Category:Japanese submarines lost with all hands

Category:Submarines sunk by United States warships