Chūyō (冲鷹,ūyō "hawk which soars") was a Taiyō-class escort carrier originally built as , the first of her class of three passenger-cargo liners built in Japan during the late 1930s. She was requisitioned by the Imperial Japanese Navy (IJN) in late 1941 and was converted into an escort carrier in 1942. She spent most of her service ferrying aircraft, cargo and passengers to Truk until she was torpedoed and sunk by an American submarine in late 1943 with heavy loss of life.
Civilian service
Nitta Maru was the lead ship of her class and was built by Mitsubishi Shipbuilding & Engineering Co. at their Nagasaki shipyard for Nippon Yusen Kaisha (NYK). She was laid down on 9 May 1938 as yard number 750, launched on 20 May 1939 and completed on 23 March 1940. The IJN subsidized all three Nitta Maru-class ships for possible conversion into auxiliary aircraft carriers. The ships were intended to upgrade NYK's passenger service to Europe and it was reported that Nitta Maru was the first ship to be fully air conditioned in the passenger quarters. The ships had accommodation for 285 passengers (127 first class, 88 second and 70 third). The start of World War II in September 1939 restricted them to the Pacific and they served on the San Francisco run until the Japanese Government declared a ban on all voyages to the United States in August 1941.
The vessel had a length of , a beam of and a depth of hold of . She had a net tonnage of 9,397 and a cargo capacity of 11,800 tons. The ship was powered by two sets of geared steam turbines made by the shipbuilder, each driving one propeller shaft, using steam produced by four water-tube boilers. The turbines were rated at a total of that gave her an average speed of and a maximum speed of .
Purchase by the navy and conversion
The ship was requisitioned for use as a military transport in February 1941. She made a few voyages, including one transferring roughly 1,200 American prisoners of war from Wake Island to Japan in January 1942. The ship departed on 12 January, arriving in Yokohama six days later. After unloading 20 men there, she departed for China. En route, the Japanese commander of the guard contingent, Lieutenant Toshio Sato, picked five men at random and ordered them topside. There they were ordered to kneel and he told them in Japanese: "You have killed many Japanese soldiers in battle. For what you have done you are now going to be killed ... as representatives of American soldiers." The Japanese then beheaded them. The bodies were used for bayonet practice and then thrown overboard.
Later that year the IJN decided to convert her to an escort carrier, matching her sisters and . The conversion took place in Kure Naval Arsenal between 1 July and 25 November 1942 and the ship was renamed Chūyō on 31 August. The Taiyō-class carriers had a flush-decked configuration that displaced at standard load and at normal load. The ships had an overall length of , a beam of and a draft of . The flight deck was long and wide and no arresting gear was fitted. They had a single hangar, approximately long, served by two centreline aircraft lifts, each . Chūyō could accommodate a total of 30 aircraft, including spares.
The changes made during the conversion limited the ship to a speed of . She carried of fuel oil that gave her a range of at a speed of . Chūyōs crew numbered 850 officers and ratings.
The ship was equipped with eight 40-caliber Type 89 dual-purpose guns in four twin mounts on sponsons along the sides of the hull. Her light AA consisted of eight license-built Type 96 light anti-aircraft (AA) guns in four twin-gun mounts, also in sponsons along the sides of the hull. In early 1943, the four twin 25 mm mounts were replaced by triple mounts and additional 25 mm guns were added. Chūyō had a total of 22 guns plus 5 license-built Type 93 anti-aircraft machineguns. The ships also received a Type 13 air search radar in a retractable installation on the flight deck at that time.
