was a light aircraft carrier of the Imperial Japanese Navy during World War II. Originally constructed as the second vessel of the seaplane tenders in 1934, she continued to operate in that capacity during the Second Sino-Japanese War and the early stages of the Pacific War until her conversion into a light aircraft carrier after the Battle of Midway. She was sunk during the Battle of Leyte Gulf by a combination of naval bombers, cruiser shellfire and destroyer-launched torpedoes.
Background
The Chitose-class seaplane tenders were procured by the Imperial Japanese Navy under the 2nd Naval Armaments Supplement Programme of 1934 as purpose-built ships, whereas their predecessors were all conversions of merchant or auxiliary ship designs. During the 1930s, the Imperial Japanese Navy made increasing use of naval aviation as scouts for its cruiser and destroyer squadrons. Due to restrictions imposed by the Washington Naval Treaty and London Naval Treaty, the number of aircraft carriers was strictly regulated; however, there was no limitation as to seaplane tenders.
Design
Chiyoda was designed from the start on the premise that the design from the waterline upwards could be modified to suit a variety of missions. The hull and engine design was based on a high speed oiler, with a maximum speed of , but the ship was completed as a seaplane tender, with four aircraft catapults for launching seaplanes, and cranes for recovering landed aircraft on her aft deck. As designed, Chiyoda carried a complement of Kawanishi E7K Type 94 "Alf" and Nakajima E8N Type 95 "Dave" floatplanes. Her armament consisted of four 12.7 cm/40 Type 89 naval guns and twelve Type 96 25 mm AA guns.
Propulsion was of four boilers, which operated two geared steam turbines providing and two propellers. With two additional diesel engines operating Chiyoda could attain .
With the loss of four large aircraft carriers at the Battle of Midway, the Imperial Japanese Navy rushed a project to convert the Chitose-class into light aircraft carriers as partial compensation. A wooden flight deck was installed, with two elevators. The bridge was moved to the front end of the new hangar deck, and the boiler exhaust gases were discharged through pipes to the starboard side below the flight deck, and the diesel engines had smaller, separate smokestacks also on the starboard side. As converted, the ship could carry 30 aircraft.
Operational history
As a seaplane tender
Chiyoda was laid down on 14 December 1936 and launched on 19 November 1937 at Kure Naval Arsenal and was commissioned on 15 December 1938. On completion, she was assigned directly to the Combined Fleet under the command of Captain Tomeo Kaku and was dispatched to the front lines in the Second Sino-Japanese War paired with the seaplane tender . She remained engaged in combat operations in China until May 1940. On returning to Kure Naval Arsenal on 23 May 1940, Chiyoda underwent her first major modification, with her aircraft capacity reduced from 24 to 12 aircraft, and the space used to store 12 Type A Kō-hyōteki-class submarines. This rebuild was completed on 23 June, and Chiyoda was assigned to the 4th Fleet based at Truk in September. Captain Kaku Harada was appointed captain in August. Chiyoda returned to participate in a naval review held on 11 October in Yokohama to celebrate the 2600th anniversary of the founding of the Japanese Empire. Afterwards, she was reassigned back to the Combined Fleet and began training operations on the use of her midget submarines through September, developing tactics for attacking other vessels (using Chitose as a target) and penetrating enemy naval bases. At the time of the attack on Pearl Harbor, Chiyoda was docked at Kure and continued training operations to 20 March 1942, when she was assigned to Vice Admiral Teruhisa Komatsu’s 6th Fleet together with the submarine tender and Aikoku Maru.
During the Battle of Midway, Chiyoda was part of Main Body of the Japanese fleet. For this operation, she carried eight Type A Kō-hyōteki-class submarines, which were intended to be stationed at Kure Atoll, which was to be seized as a seaplane base for operations against Midway Atoll. The operation was cancelled on the loss of the Japanese aircraft carriers during the Battle of Midway, and Chiyoda returned to Hashirajima with her submarines on 14 June without having seen combat.