Japanese aircraft carrier Hiyō

Japanese aircraft carrier Hiyō was a Hiyō-class aircraft carrier that served with the Imperial Japanese Navy during World War II. Originally laid down as the ocean liner , she was purchased by the Imperial Japanese Navy in 1941 while still under construction and converted into an aircraft carrier. *Hiyō* participated in several major campaigns in the Pacific War, including the Battle of the Santa Cruz Islands and the Battle of the Philippine Sea, where she was ultimately sunk.

Design and construction

The ship was originally ordered by Nippon Yusen Kaisha as the luxury passenger liner *Izumo Maru*, part of a planned pair with her sister ship . Her design was based on the earlier but was intended for higher speed to maintain a regular trans-Pacific schedule. Following the outbreak of World War II and the Imperial Japanese Navy's urgent need for additional aircraft carriers, the unfinished hull was purchased by the navy in February 1941. Conversion work began immediately at the Kawasaki Heavy Industries shipyard in Kobe. The design retained the liner's basic hull form and geared steam turbine machinery, which limited her top speed compared to purpose-built fleet carriers. The conversion added a single hangar deck, a full-length flight deck fitted with two aircraft catapults, and an island superstructure on the starboard side. Her anti-aircraft armament at commissioning consisted of twelve Type 89 127 mm (5.0 in) guns and numerous lighter Type 96 25 mm AT/AA Guns.

Service history

Commissioned on 31 July 1942, *Hiyō* was assigned to the Second Carrier Division. After working up in the Inland Sea, she was dispatched to the Southwest Pacific in October 1942. She participated in the Battle of the Santa Cruz Islands as part of the Main Body under Vice Admiral Nobutake Kondō, though her air group saw limited action. In 1943, she operated between Truk Lagoon and the Japanese home islands, transporting aircraft and providing cover for convoys. She was torpedoed by the United States Navy submarine in June 1943 near Tokyo Bay, requiring extensive repairs that kept her out of action for several months. She returned to service in late 1943 and was involved in operations against Allied forces in the Gilbert and Marshall Islands campaign. In 1944, she was assigned to the First Mobile Fleet under Vice Admiral Jisaburō Ozawa for the defense of the Mariana Islands.

Aircraft complement and air group operations

*Hiyō*'s air group composition evolved throughout the war, reflecting the changing fortunes of Japanese naval aviation. Initially, her aircraft complement included a mix of Mitsubishi A6M Zero fighters, Aichi D3A "Val" dive bombers, and Nakajima B5N "Kate" torpedo bombers. Her air group, designated the 652nd Naval Air Group for the Battle of the Philippine Sea, was drawn from the veteran 601st Naval Air Group but suffered from a severe shortage of experienced pilots due to earlier attrition in battles like the Solomon Islands campaign. During the Battle of the Santa Cruz Islands, her aircraft contributed to strikes against Task Force 16 and Task Force 17. By 1944, her group was equipped with newer types like the Yokosuka D4Y "Judy" dive bomber, but pilot quality had drastically declined, impacting operational effectiveness during the Great Marianas Turkey Shoot.

Loss

*Hiyō* was sunk on 20 June 1944 during the Battle of the Philippine Sea. As part of Vice Admiral Jisaburō Ozawa's First Mobile Fleet, she launched strikes against the United States Fifth Fleet under Admiral Raymond Spruance. During the American counterstrike in the evening, she was attacked by aircraft from the Task Force 58 carriers and . Hit by at least one aerial torpedo from a Grumman TBF Avenger and several bombs, her starboard engine room flooded and a severe fire ignited aviation fuel vapors. The resulting explosions and uncontrollable fires led to her abandonment. She sank bow-first approximately 500 kilometers west-northwest of Saipan. The destroyers and rescued survivors, including her captain, Vice Admiral Jojima Takatsugu, but over 250 crewmen were lost.

Legacy

The loss of *Hiyō* and two other carriers during the Battle of the Philippine Sea was a catastrophic blow to the Imperial Japanese Navy's carrier force, effectively ending its ability to conduct large-scale, organized carrier operations for the remainder of the war. Her design, as a converted liner, highlighted the Imperial Japanese Navy's improvisation in expanding its carrier fleet but also underscored the limitations such vessels faced against purpose-built American *Essex*-class carriers. Along with her sister *Jun'yō*, she represented a distinct class within the Japanese carrier fleet. Her wreck has not been definitively located. The story of *Hiyō* is examined in historical studies of the Pacific War, including works by historians such as Jonathan Parshall and Anthony Tully.

Category:Aircraft carriers of the Imperial Japanese Navy Category:World War II aircraft carriers of Japan Category: Hiyō-class aircraft carrier