Hiyō

Hiyō
Public domain · source
Ship caption	Hiyō underway in 1943
Ship country	Empire of Japan
Ship name	Hiyō
Ship ordered	1939
Ship builder	Kawasaki Shipbuilding Corporation
Ship laid down	30 November 1939
Ship launched	24 June 1941
Ship commissioned	31 July 1942
Ship fate	Sunk 20 June 1944
Ship class	Hiyō-class aircraft carrier
Ship displacement	24,150 tons (standard)
Ship length	219.32 m (719 ft 7 in)
Ship beam	26.7 m (87 ft 7 in)
Ship draught	8.15 m (26 ft 9 in)
Ship propulsion	Geared steam turbines, 2 shafts
Ship speed	25.5 knots (47.2 km/h)
Ship complement	1,224
Ship aircraft	53
Ship armament	12 × 127 mm (5 in) DP guns, 24 × 25 mm AA guns
Ship armor	Belt: 50 mm (2 in), Deck: 25 mm (1 in)

Hiyō. Hiyō was a Hiyō-class aircraft carrier that served with the Imperial Japanese Navy during the Pacific War. Originally laid down as the fast passenger liner *Izumo Maru* for Nippon Yusen Kaisha, she was purchased by the Imperial Japanese Navy in 1941 while still under construction and converted into an aircraft carrier. Commissioned in mid-1942, she saw extensive action in several major campaigns before her loss in 1944.

Design and construction

The ship was initially ordered in 1939 as part of a planned class of luxury passenger liners intended for service between Japan and the West Coast of the United States. Her keel was laid down at the Kōbe yard of the Kawasaki Shipbuilding Corporation. Following the outbreak of the Second Sino-Japanese War and increasing tensions with the United States, the Imperial Japanese Navy requisitioned the unfinished hull in February 1941 for conversion into an aircraft carrier. The design was similar to her sister ship, Jun'yō, featuring a full-length flight deck, a single starboard-side island, and two main aircraft elevators. Her machinery, consisting of geared steam turbines driving two propellers, was originally intended for high-speed liner service but proved less reliable under naval combat conditions. Her anti-aircraft armament was progressively strengthened throughout her career in response to the growing threat from United States Navy aircraft.

Service history

After commissioning, Hiyō was assigned to the Combined Fleet and underwent intensive working-up exercises in the Seto Inland Sea. Her first major operation was during the Guadalcanal campaign, where she provided distant cover for reinforcement convoys. In 1943, she was deployed to the North Pacific following the Battle of the Aleutian Islands, ferrying aircraft to Paramushir. She later participated in the failed reinforcement of Biak in New Guinea in mid-1944. Her most significant action was as part of Vice Admiral Jisaburō Ozawa's First Mobile Fleet during the Battle of the Philippine Sea in June 1944. During this pivotal engagement, her air group suffered catastrophic losses in the so-called "Great Marianas Turkey Shoot" before the carrier itself was targeted.

Aircraft and air group

Throughout her career, Hiyō's air group composition evolved with the fortunes of Japanese naval aviation. Initially equipped with a mix of Mitsubishi A6M Zero fighters, Aichi D3A "Val" dive bombers, and Nakajima B5N "Kate" torpedo bombers, her squadrons participated in numerous missions across the South Pacific. By the time of the Battle of the Philippine Sea, her air group, like those aboard Taihō and Shōkaku, was largely composed of inexperienced pilots facing veteran United States Navy aviators flying advanced aircraft like the Grumman F6F Hellcat. The carrier typically operated between 50 and 60 aircraft, though this number often fluctuated due to combat losses and difficulties in pilot training and replacement.

Loss

Hiyō was sunk on 20 June 1944 during the Battle of the Philippine Sea. While retiring westward after the disastrous air battles of the previous day, she was attacked by aircraft from the USS *Belleau Wood* and USS *Yorktown*. A torpedo hit from a Grumman TBF Avenger caused severe damage, flooding machinery spaces and leading to a loss of power. Subsequent explosions, likely from aviation fuel vapors, sealed her fate. The destroyers *Maki* and Hayanami rescued survivors, including her captain, before she sank north-northwest of Chichijima. The sinking of Hiyō, along with Shōkaku and Taihō in the same battle, crippled the offensive capability of the First Mobile Fleet.

Legacy

Hiyō's career exemplifies the trajectory of Japanese carrier aviation in the Pacific War: a hastily converted vessel that entered service as the Imperial Japanese Navy reached its zenith at the Battle of Midway, and was then worn down in the grueling attritional campaigns that followed. Her loss during the Battle of the Philippine Sea marked a decisive turning point, leaving Japan unable to effectively challenge American naval air power for the remainder of the war. The wreck of Hiyō has not been definitively located, lying with many other warships lost in the deep waters of the Philippine Sea.

Category:Aircraft carriers of the Imperial Japanese Navy Category:Hiyō-class aircraft carriers Category:World War II aircraft carriers of Japan Category:Ships built in Kobe Category:Maritime incidents in June 1944