Japanese cruiser Ōyodo

300px Ōyodo in 1943 at Kure Naval Arsenal, Hiroshima Floatplane launcher is larger than later type.
Class overview
Operators:	Imperial Japanese Navy
Preceded by:	Agano class
Built:	1941-43
In service:	1943-45
In commission:	1943-45
Planned:	2
Completed:	1
Lost:	1
History
Empire of Japan
Name:	Ōyodo
Namesake:	Ōyodo River
Ordered:	1939
Laid down:	14 February 1941
Launched:	2 April 1942
Commissioned:	28 February 1943
Struck:	20 November 1945
Fate:	sunk 28 July 1945 bombed by USN aircraft at Kure Naval Base
Notes:	raised and scrapped 1 August 1948
General characteristics
Class & type:	none
Type:	Cruiser
Displacement:	8,164 long tons (8,295 t) (standard) 11,433 long tons (11,616 t) (full load)
Length:	192 metres (629 feet 11 inches)
Beam:	15.7 metres (51 feet 6 inches)
Draught:	5.95 metres (19 feet 6 inches)
Installed power:	110,000 shp (82,000 kW)
Propulsion:	Geared turbines, 4 shafts 6 Kampon boilers
Speed:	34 kn (63.0 km/h; 39.1 mph)
Range:	10,600 nautical miles (19,600 kilometres) at 18 knots (33 km/h)
Complement:	782 (initial); 911 (final)
Armament:	6 × 155 mm (6.1inch)/60 cal. 3rd Year Type guns (2 × 3) 8 × 100 mm (3.9inch)/65 cal. Type 98 AA guns (4 × 2) 18 × Type 96 25mm AA guns, (6×3, 1943) 52 × Type 96 25mm AA guns, (12×3 + 16x1, 1945)
Armor:	Side belt 60 mm (2.4 in) Deck 30–50 mm (1.2–2.0 in) Turrets/Barbettes 25–30 mm (0.98–1.18 in) Conning tower 40 mm (1.6 in)
Aircraft carried:	6 × floatplanes (1943), 2 × floatplanes (1944)

Ōyodo (大淀 ), was a light cruiser of the Imperial Japanese Navy (IJN), completed during World War II, and was the only ship of her class completed before the end of the war. As was the practice with IJN light cruisers, she was named after a river, in this case the Ōyodo River in Kyūshū, Japan. Intended as a command vessel for submarine operations, she was used for a variety of missions, and became the flagship of the Combined Fleet before being sunk by American aircraft at Kure, Hiroshima in July 1945.

Background

The Imperial Japanese Navy 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 Agano-class cruisers would be able to serve in this role, but proved unsatisfactory. By the late 1930s, the Japanese Navy had defined the need for seven cruisers to support its seven submarine squadrons. After several design iterations, funding for the first two vessels was approved under the 1939 4th Replenishment Program, of which only one, Ōyodo, was laid down; the second ship was to be named Niyodo. Immediately after Ōyodo was completed, all available shipbuilding resources at the Kure Naval Arsenal were diverted to build more aircraft carriers.

Design

The Ōyodo design was as an enlarged and improved version of the Agano-class cruiser. Ōyodo retained the same general hull design as the cruiser Agano, with a flush deck and bulbous bow: however, her armament differed both in layout and weaponry, and her armour protection was reduced.

Propulsion was by four sets of Kampon geared turbines, rated at 110,000 shp (82,000 kW), which was more powerful than that of the Agano class, and which provided a maximum speed of 35 knots (65 km/h; 40 mph). Ōyodo had a design range of 8,700 nautical miles (16,100 km; 10,000 mi) at 18 knots (33 km/h; 21 mph), but an actual range of 10,500 nautical miles (19,400 kilometres; 12,100 miles).

Ōyodo's main armament comprised six 155 mm (6.1 inch)/60 cal. 3rd Year Type guns in two triple-gun turrets. This gun was originally developed as a dual purpose (anti-surface and anti-aircraft) weapon for the Mogami class; when those ships underwent reconstruction in the 1930s and had their triple 155 mm turrets replaced with 203 mm (8 inch) twin turrets, the now-surplus triple 155 mm turrets were mounted on Ōyodo (as well as the Yamato-class battleships). Their slow rate of fire (5 to 6 rounds per minute) and limited elevation (up to only 55 degrees) made them unsuitable for the anti-aircraft role, but they were excellent anti-ship weapons.

Ōyodo's heavy anti-aircraft battery comprised eight 100 mm/65 calibre Type 98 guns in four twin mounts. These guns were the same as that carried by the Akizuki-class destroyers and the never-built B64-class cruisers. The performance of this weapon was superb, and it is considered to be the best Japanese heavy anti-aircraft (AA) gun of the war. Their main fault was a rather short service life, the result of a high muzzle velocity (1,000 m/s) and a fast rate of fire (15–20 rounds per minute). The remaining AA armament consisted of the 25 mm/60 caliber Type 96 AA gun, which was based on a French Hotchkiss design but was a very mediocre AA weapon with a low effective rate of fire, slow elevation and training, and lack of effective remote power control.

The main armament was all located forward of the superstructure, much like the British Nelson-class battleship, French Dunkerque and Richelieu-class battleships and the Japanese Navy's own Tone-class heavy cruisers. Like the Tone class, 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. Indeed, again in view of their intended role, no torpedo tubes were fitted, making the Ōyodo class the sole class of cruisers in the Imperial Japanese Navy without these weapons. The weight thus saved was invested instead in increased floatplane capacity (up to six) and a heavy-duty 45 m (148 ft) catapult that was necessary for the new E15K1 Shiun floatplane.

The E15K1 ‘‘Shiun’’ floatplane (Allied codename "Norm") was intended to perform reconnaissance for the submarine flotilla in areas where the enemy had air superiority, and hence was to be able to take on land-based fighters. To achieve this, the plane was designed with two underwing stabilizing floats that could be retracted, and a large central float that could be jettisoned, to increase performance during combat. However, while incorporating this and several other innovations, the plane never really worked as designed and its troubled development resulted in only four aircraft entering service by 1942, and only fifteen were completed in total. Six were sent to Palau where Ōyodo was operating for operational testing. Despite a more powerful engine, the performance of the E15K1's (being about 500 kg heavier than the more common Aichi E13A1 "Jake") was poor and they were quickly lost to attacking fighters. As a result, production of the aircraft, which had barely begun, was stopped and the entire E15K1 program shelved in early 1944. Ōyodo hence never operated more than two aircraft, particularly after her refit later in which her large hangar was converted to other uses.

Service career

Ōyodo was laid down at Kure Naval Arsenal on 14 February 1941, launched on 2 April 1942 and completed 28 February 1943. Her chief equipping officer and first commander was Captain Sadatoshi Tomioka. However, by the time of her completion, the role for which Ōyodo was designed no longer existed. Instead, the Japanese navy made use of her long range and anti-aircraft capability as an escort for carrier groups. Originally completed without any radar, a Type 21 radar set was installed in March 1943.

Early career

After her working-up period, on 15 July 1943 Ōyodo arrived at Truk, Caroline Islands, the Japanese Navy's main fleet base in the Pacific, and continued on to Rabaul to deliver reinforcements and supplies. In mid-September, In response to American carrier aircraft raiding in the Gilbert Islands, Ōyodo sortied with Vice Admiral Jisaburō Ozawa's fleet to engage the American carriers. The fleet consisted of the aircraft carriers Shōkaku, Zuikaku and Zuihō, the battleships Yamato and Nagato, heavy cruisers Myōkō, Haguro, Tone, Chikuma, Mogami, Atago, Takao, Chōkai and Maya, the light cruiser Agano and fifteen destroyers. Despite extensive searches, this force failed to make contact with the American striking force and returned to Truk. A second mission in mid-October likewise failed to produce any results.

On 30 December 1943, Ōyodo participated in an operation to reinforce the garrisons at Rabaul and Kavieng. Ōyodo had become the flagship of Vice Admiral Jisaburō Ozawa's Third Fleet on 6 December. While returning to Truk on 1 January 1944, Ōyodo was slightly damaged by US aircraft 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. She 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

File:Japanese cruiser Oyodo in 1944.jpg

Ōyodo in 1944

By the start of 1944, it was recognised from the progress of the war and the failure of the E15K1 floatplane program that Ōyodo would not be able to fulfill her original design role. On 6 March, Ōyodo went into the dry dock at Yokosuka for a refit, in which her hangar was converted to crew quarters, and the former crew quarters converted into staff wardrooms. The aircraft catapult was reduced to the shorter (18 m or 59 ft) standard type, and a Type 22 surface search radar installed. An additional six Type 96 triple-mount, and eleven Type 96 single-mount anti-aircraft guns were installed. On completion of the refit on 31 March, Ōyodo was designated the flagship of the Combined Fleet, and Admiral Soemu Toyoda CINC of the Combined Fleet, transferred his flag on 30 April in a ceremony in Tokyo Bay .

Ōyodo remained in Tokyo Bay until 22 May, was anchored at Hashirajima until 25 June, and anchored again in Tokyo Bay until 11 October. On 29 September, Admiral Toyoda and his staff moved from Ōyodo to the new underground headquarters of the IJN in Yokohama. Around this time, an additional six Type 96 AA guns were installed, along with a Type 13 radar and two Type 22 radar sets. Ōyodo departed Yokosuka on 11 October, and was attacked by the submarine USS Trepang which fired six torpedoes, all of which missed .

Ōyodo departed Yashima anchorage on 20 October 1944 towards the Philippines as part of Operation “Sho-Ichi-Go”— or the Battle of Leyte Gulf. The objective of the operation was to repel the American invasion of the Philippines. Ōyodo was part of Vice Admiral Ozawa's Northern Mobile ("Decoy") Force, which was to bait the American aircraft carrier strike force away from the main Japanese strike force. The decoy force included one fleet carrier, three light carriers, two battleship-carrier hybrids (with perhaps 100 aircraft between them), cruisers and destroyers. Ōyodo was the only warship in Ozawa's force that had reconnaissance floatplanes, and both E13A1's performed reconnaissance and anti-submarine patrols over the fleet . On 25 October 1944, off Cape Engaño, the Northern Mobile Force was attacked by Vice Admiral Marc A. Mitscher's Task Force 38 carrier planes in a massive strike consisting 527 sorties in five strikes. During the first strike, Ōyodo suffered two near-misses, but at 0848 she was hit by a bomb that damaged her Number 4 boiler room. At 1054, Vice Admiral Ozawa left the sinking carrier Zuikaku and transferred his flag to Ōyodo. During the engagement, in addition to Zuikaku, the Japanese lost the aircraft carriers Zuihō and Chitose, and destroyer Akizuki. Ōyodo was hit by two rockets from F6F Hellcat fighter-bombers and damaged by the near-miss of a bomb. Ozawa ordered his remaining forces to retire northward. Ozawa soon received word that an American cruiser squadron was attacking the destroyers left behind to rescue survivors, and Ōyodo was ordered to reverse course. However, before she could arrive, the cruisers had sunk the aircraft carrier Chiyoda with all hands and the destroyer Hatsuzuki. Ōyodo and the surviving ships arrived at Amami-Oshima the next day.

Final stages of the war

Ōyodo sunk in shallow waters near Kure

A few days later Ōyodo was sent to Manila on a transport run, arriving on 1 November 1944. Throughout the remainder of the year, Ōyodo was actively involved in numerous operations around Brunei, Camranh and the Philippines, attacking US convoys, bombarding landing sites and engaging US naval forces in the area. Although other ships with her were either damaged or sunk during the sorties, Ōyodo emerged unscathed.

By January 1945, Ōyodo had arrived in Singapore, where she took on 300 tons of rubber, zinc, mercury, tin and petrol. Other ships in her unit were similarly loaded with critical war supplies bound for Japan. On 11 February 1945 Ōyodo's unit, the "Completion Force", left Singapore for Japan in what was designated Operation Kita, and along the way escaped pursuit and dodged attacks by twenty-three Allied submarines, and arrived at Kure on 20 February 1945.

Ōyodo remained at Kure for the remainder of the war, and on 19 March 1945, Vice Admiral Marc A. Mitscher's Task Force 58 aircraft carriers made the first carrier attack on the Kure Arsenal. More than 240 aircraft (SB2C Helldiver dive bombers, F4U Corsair and F6F Hellcat fighter-bombers) attacked the Japanese fleet. Three 500 pounds (227 kg) bombs hit Ōyodo; she started to flood, but was towed to Etajima and beached. However, she was quickly repaired, and combat-ready again by 4 April. On 24 July 1945 US Task Force 38 launched a massive attack to destroy any and all remaining units of the Japanese Navy. Ōyodo was strafed and hit by four 500-pound bombs and many near misses that left her listing to starboard. Four days later, another all-day-long attack was launched by the US carrier fleet. Ōyodo was hit by four more bombs; at 1000 hours, hits near the bridge caused extensive flooding and Ōyodo took on a heavy list to starboard. At 1200, she capsized to starboard in shallow water. With about 300 crewmen killed, her remaining crew abandoned ship that afternoon .

Ōyodo was removed from the navy list on 20 November 1945. The wreck of Ōyodo was raised 18–20 September 1947 and towed to Kure on 20 December 1947. The ship was scrapped at Kure - the shipyard where she was completed only a few years previously - from 17 January to 1 August 1948.

Ships in class

Ship #	Ship	Laid down	Launched	Completed	Fate
136	Ōyodo (大淀)	14 February 1941	2 April 1942	28 February 1943	Sunk by air raid on 28 July 1945
137	Niyodo (仁淀)	Cancelled on 6 November 1941