was an escort carrier operated by the Imperial Japanese Navy (IJN) during World War II. The ship was originally built as the ocean liner Argentina Maru. She was purchased by the IJN on 9 December 1942, converted into an escort carrier, and renamed Kaiyō. The ship was primarily used as an aircraft transport, escort carrier and training ship during the war. She was badly damaged by repeated air attacks in July 1945 and was scrapped in 1946–48.
Description
The ship was ordered as the fast luxury passenger liner Argentina Maru by Osaka Shosen Kaisha (OSK) in 1938. In exchange for a subsidy of her building costs by the Navy Ministry, she was designed to be converted to an aircraft carrier.
Argentina Maru was completed in 1939 and rated at . After being rebuilt, the ship had a length of overall. She had a beam of and a draft of . She displaced at standard load. As part of her conversion, her original diesel engines, which had given her a top speed of , were replaced by a pair of destroyer-type geared steam turbine sets with a total of , each driving one propeller. Steam was provided by four water-tube boilers and Kaiyō now had a maximum speed of . She carried enough fuel oil to give her a radius of . Her crew numbered 829 officers and men.
The ship's flight deck was wide and Kaiyō had a single hangar, served by two aircraft elevators, mounted on the centerline. She was not built with an island and could operate 24 aircraft. The ship's primary armament consisted of eight 40-caliber 12.7 cm Type 89 anti-aircraft (AA) guns in twin mounts on sponsons along the sides of the hull. They fired projectiles at a rate between 8 and 14 rounds per minute at a muzzle velocity of ; at 45°, this provided a maximum range of , and a maximum ceiling of . Kaiyō was also initially equipped with eight triple 25 mm Type 96 light AA guns, also in sponsons along the sides of the hull. They fired projectiles at a muzzle velocity of ; at 50°, this provided a maximum range of , and an effective ceiling of . The maximum effective rate of fire was only between 110 and 120 rounds per minute due to the frequent need to change the fifteen-round magazines. In early July 1944, 20 single 25 mm guns were added as were eight depth charges. Some sources say that a number of 28-round AA rocket launchers were added in late 1944. Each rocket weighed and had a maximum velocity of . Their maximum range was . Early warning was provided by a Type 2, Mark 2, Model 1 air search radar that was installed on the side of the flight deck in November 1943.
Service history
Argentina Maru was initially used for troop transport after the beginning of the Pacific War in December 1941. The ship began conversion at Nagasaki on 10 December 1942, the day after she was purchased. After the conversion was completed on 23 November 1943, she was renamed Kaiyō. Her initial duties were to transport aircraft to Japanese overseas bases. Her first such task was to ferry aircraft for the 23rd Air Flotilla to Singapore via Manila in January 1944 as part of Convoy HI-33. On her return journey, the ship transported aircraft of the 551st Air Group to Truk. On 10 February, en route to Truk from Palau, the submarine made a night attack on Kaiyō, but the torpedoes missed. Kaiyō was briefly refitted between 23 February and 2 March and was assigned to the 1st Surface Escort Division on 17 March. She escorted Convoy HI-57 to Singapore via Taiwan and Indochina in April. She escorted Convoy HI-58 on the return voyage; one of her aircraft spotted the submarine on the surface behind the convoy. The submarine was damaged by the escorts, but escaped.
In late May, Kaiyō formed part of the escort for Convoy HI-65, together with the escort carrier , bound for Singapore. One of the escorts was torpedoed en route and two of the merchantmen collided while trying to dodge the other torpedoes. The rest of the convoy arrived at Singapore on 12 June. Kaiyō was assigned to fast Convoy HI-66 for the return voyage and reached Japan on 26 June. She was briefly docked at Kure Naval Arsenal in early July to have more 25 mm AA guns fitted. Together with the escort carrier , Kaiyō was loaded with aircraft bound for the Philippines to be delivered in Convoy HI-69. They departed on 13 July and arrived a week later. The convoy left Manila four days later and reached Japan on 1 August. The ship's machinery broke down as she was preparing to join another convoy on 4 August and she was transferred to Sasebo.