IJN Chiyoda began service with the Imperial Japanese Navy (IJN) as a dedicated seaplane tender as part of the two-strong Chitose-class aircraft carrier group. Ordered in 1934 she was built at the Kure Naval Arsenal where the keel was laid down on December 14th, 1936. Launched on November 19th, 1937, the warship was formally commissioned on December 15th, 1938.
Chiyoda managed an existence in her seaplane tender role during the Second Sino-Japanese War (July 1937 - September 1945) and throughout the early-going of the Pacific Campaign of World War 2 (1939-1945). However, after the devastating loss of four aircraft carriers in the Battle of Midway (June 4th - June 7th, 1942), Chiyoda was ordered for reconstruction as a dedicated light fleet carrier.
Changes made allowed the onboard aircraft total to be increased from the original 24 floatplanes to 30 combat aircraft. A pair of deck elevators were added to facilitate movement of aircraft from below deck to the flight deck. The bridge structure was relocated forward while engine exhaust ports were run along starboard side. Defensive armament was increased from 4 x 12.7mm machine guns and 12 x 25mm autocannons to 8 x 12.7mm machine guns and up to 48 x 25mm autocannons. Propulsion power stemmed from 2 x geared steam turbines generating 56,000 horsepower and driving 2 x shafts to speeds of nearly 29 knots. Dimensions included a length of 631.6 feet, a beam of 68.3 feet and a draught of 24.6 feet.
The reconstruction work spanned from 1942 until 1944 and the ship was recommissioned as a light fleet carrier back on December 21st, 1943.
Her first actions in the new role centered on support at Kwaljalein and then the Mariana Islands. She then participated in the Battle of the Philippine Sea on June 19th, 1944 and took a bomb which damaged her and forced repairs at Kure into July. Her end came during the Battle of Leyte Gulf on October 25th, 1944 when the warship was subject to multiple direct hits from American naval guns, aerial bombs and torpedoes. 1,470 crew went down with the crippled Chiyoda.
IJN Chiyoda was struck from the Naval Register on December 20th, 1944.