was a light cruiser built for the Imperial Japanese Navy (IJN) during World War II, and was the only ship of her class completed before the end of the war. Designed to command submarine operations, she was obsolete upon completion in 1943. The ship was used as a transport and to escort the navy's capital ships for the rest of the year. Ōyodo was lightly damaged by American aircraft in early January 1944 during one transport mission and returned home several months later to begin conversion to serve as the flagship of the Combined Fleet.
The ship reverted to her previous roles when the headquarters of the Combined Fleet was moved ashore in September. The following month, she participated in the Battle off Cape Engaño, where she escorted the Japanese carriers attempting to decoy the American carrier fleet supporting the invasion of Leyte away from the landing beaches. Afterwards, the ship was transferred to Southeast Asia and engaged American forces in the Philippines in December where she was slightly damaged by American bombers. In early 1945, Ōyodo participated in Operation Kita, during which she transported aviation gasoline and other strategic materials back to Japan. The ship was damaged by American carrier aircraft in March and repairs were completed two months later. She was sunk with the loss of about 300 men during American airstrikes in July. After the war, Ōyodo was salvaged and scrapped in 1947–1948.
Background The IJN's concept of submarine warfare was to use long-range submarines in squadrons (sentai) to attack enemy units at extended ranges. These submarines would be coordinated by a cruiser, which would use reconnaissance aircraft to provide targeting information. Originally, it was intended that the s would be able to serve in this role, but they proved unsatisfactory. By the late 1930s, the Japanese Navy had defined the need for seven cruisers to support its seven submarine squadrons. Funding for the first two vessels was approved under the 1939 4th Replenishment Program, of which only one, Ōyodo, was begun.Stille, p. 39 Construction of the second ship, intended to be named Niyodo, was suspended on 6 November 1941 because Ōyodo still occupied her intended slipway and was finally cancelled on 3 August 1942.Lacroix & Wells, pp. 617–618
Design and description Ōyodos design was derived from that of the . Ōyodo retained the same general hull design with a flush deck and bulbous bow, but her superstructure and armament differed to suit her different role.Lengerer, p. 102 Ōyodo had a length of overall, a beam of and a draft of . The ship displaced and had a metacentric height of at deep load. Her crew numbered 33 officers and 532 enlisted men as completed.Lacroix & Wells, pp. 624, 645, 831
Ōyodo was powered by four geared steam turbine sets, each driving a single three-bladed propeller, using steam provided by six Kampon water-tube boilers that operated at a pressure of and a temperature of . The turbines were designed to produce for a speed of . The ship exceeded her designed speed during her sea trials reaching from . She stowed of fuel oil,Lengerer, pp. 104–105 which gave her a range of at .Jentshura, Jung & Mickel, p. 112 Ōyodo had three turbo generators of capacity and two diesel generators.Lacroix & Wells, p. 637
Armament and fire control The ship's main battery comprised six 50-caliber 155 mm (6.1 in) 3rd Year Type guns in two triple-gun turrets superfiring forward of the superstructure.Lengerer, p. 106 The gun was originally developed as a dual-purpose (anti-surface and anti-aircraft) weapon for the ; when they had their triple 155 mm turrets replaced with twin 203 mm (8 in) turrets, the now-surplus turrets were mounted on Ōyodo (as well as the s). Their slow rate of fire of 5 rounds per minute and limited elevation (up to only 55 degrees) made them unsuitable for the anti-aircraft role. The guns fired shells at a muzzle velocity of to a maximum range of at +45 degrees of elevation. Each gun was provided with 150 rounds.Lacroix & Wells, pp. 459, 462
Ōyodos heavy anti-aircraft battery consisted of eight 65-caliber 100 mm (3.9 in) Type 98 dual-purpose guns in four twin mounts. The mounts had a range of elevation from -10 degrees to +90 degrees and the guns had a muzzle velocity of with their projectiles. They had a range of and a height of at maximum elevation.Campbell, p. 196 The anti-aircraft armament was completed by eighteen 60-caliber Type 96 light AA guns in six triple mounts. Firing shells at a muzzle velocity of . These guns had an effective range of , and an effective ceiling of at an elevation of 85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the frequent need to change the fifteen-round magazines.Campbell, p. 200
The ship was equipped with a director-control tower above the bridge with a Type 94 gunnery director controlling the main armament. The director was fitted with a rangefinder and the upper gun turret mounted a rangefinder. The Type 98 10 cm guns were controlled by a pair of Type 94 directors positioned at the base of the bridge and the light AA guns were provided with three Type 95 directors, all on the forward superstructure.
Aircraft Like the heavy cruisers, the Ōyodo-class ships were intended to be scouting cruisers and hence the entire deck of the ship aft of the superstructure was devoted to aircraft facilities. The weight saved by not fitting torpedo tubes was invested instead in a hangar that could house four floatplanes, with two more stowed on deck, and a heavy-duty catapult that was necessary for the new Kawanishi E15K Shiun floatplane (Allied reporting name "Norm") that was intended to perform reconnaissance for the submarine flotilla in areas where the enemy had air superiority. To achieve this, the plane was designed with two retractable underwing stabilizing floats and a large central float that could be jettisoned to increase speed. However, the aircraft performed poorly and only fifteen were completed before it was canceled in February 1944. Ōyodo did carry two or three Aichi E13A "Jake" reconnaissance floatplanes during her career.Lacroix & Wells, p. 628; Lengerer, p. 106
Protection The ship's armor was designed to protect against 155 mm shells and bombs dropped from an altitude of . It had a waterline belt had a maximum thickness of of copper alloy homogeneous armor that protected the propulsion machinery and the bomb magazine; it extended above the waterline and below. The armored deck rested on the upper edge of the belt armor and was thick except over the bomb magazine where it increased to . The ends of the belt armor were closed off by transverse bulkheads that also increased to 50 mm adjacent to the bomb magazine. The magazine itself had 35 mm sides and a 25 mm front. The steering gear aft was protected by an armored box with sides, a front and a 25 mm rear.Lacroix & Wells, pp. 620–624; Lengerer, p. 103
Forward of the boiler rooms, the fire-control center, the 25 mm and 155 mm magazines had armored sides. The latter magazine had plates that tapered to 40 mm at their lower edge. The armor on the other compartments was 60 mm thick reducing to 30 mm at the bottom. The roof of these spaces was 50 mm thick over the 155 mm magazines and reduced to 28 mm over the other compartments. The main gun turrets were protected by 25 mm homogeneous armor plates and their barbettes had 20 mm or 25 mm thick plates. The sides of the conning tower were 40 mm thick and it had a roof 20 mm thick.Lacroix & Wells, pp. 460, 621–624; Lengerer, pp. 103–104
Construction and career Following the Japanese ship-naming conventions for light cruisers, the ship was named after the Ōyodo River in Kyūshū. Ōyodo was laid down at Kure Naval Arsenal on 14 February 1941, launched on 2 April 1942 and completed on 28 February 1943 under the command of Captain Sadatoshi Tomioka. Completed without any radar, a Type 21 early-warning radar was installed in April 1943 while the ship was still working up.
The war had developed in ways unanticipated by the IJN and her designed role as a submarine flotilla flagship was no longer necessary or even possible, so the navy settled on using her as an ordinary light cruiser or as a transport.Lengerer, pp. 108–109 On 1 April, she was assigned to the Third Fleet and was transferred to the Main Body, Mobile Force, a month later. In response to the invasion of Attu Island on 11 May, Ōyodo rendezvoused with three battleships, two aircraft carriers and five heavy cruisers in Tokyo Bay on 22 May. The Americans recaptured Attu before the fleet could depart to counterattack. The following month the ship received a brief refit in Kure.
She loaded troops and supplies on 9 July at Shinagawa and, arrived at Truk, Caroline Islands, on 15 July before continuing on to Rabaul where she arrived on the 21st, returning to Truk five days later and rejoining the Third Fleet. In response to the carrier raid on Tarawa on 18 September, much of the fleet sortied for Eniwetok to search for the American forces before they returned to Truk on 23 September, having failed to locate them. The Japanese had intercepted some American radio traffic that suggested another attack on Wake Island, and on 17 October, Ōyodo and the bulk of the fleet sailed for Eniwetok to be in a position to intercept any such attack, but no attack occurred and the fleet returned to Truk.Hackett & Kingsepp
Vice Admiral Jisaburō Ozawa, commander of the Third Fleet, hoisted his flag aboard the ship on 6 December. On 30 December Ōyodo participated in an operation to reinforce the garrisons at Rabaul and Kavieng. While returning to Truk on 1 January 1944, Ōyodo was slightly damaged by US aircraft from two aircraft carriers of Task Group 50.2, with two crewmen killed and six wounded. The following day, she rescued 71 survivors from the transport Kiyosumi Maru, which had been torpedoed by an American submarine. Ōyodo returned to Yokosuka on 16 February following the successful American invasion of Kwajalein, and loaded torpedoes and supplies for the Japanese garrison at Saipan, which were delivered on 22 February.
Flagship of the Combined Fleet and the Battle off Cape Engaño
On 6 March, Ōyodo went into the dry dock at Yokosuka for a refit to convert her into a flagship, in which her hangar was converted into staff offices and accommodations to take advantage of her elaborate communications suite. The aircraft catapult was exchanged for the shorter () standard type, and a pair of Type 22 surface search radars were installed. 29 additional Type 96 guns were installed in six triple and eleven single mounts for a total of 47 weapons. The modifications increased her complement to 61 officers and 850 sailors. The day after the refit was finished on 31 March, Ōyodo became the flagship of the Combined Fleet. Admiral Soemu Toyoda, commander of the Combined Fleet, hoisted his flag on her on 4 May. Ōyodo remained in Japanese waters until 11 October. On 29 September, Admiral Toyoda and his staff transferred to the new underground headquarters of the IJN in Yokohama. Six additional Type 96 AA guns in single mounts were installed in early October, along with a Type 13 radar, and her Type 22 radars were modified to allow them to be used for fire control.Lacroix & Wells, pp. 627, 632, 645; Lengerer, pp. 106, 108–109