was the second and last built for the Imperial Japanese Navy (IJN) during the 1910s. Although completed in 1918, she played no role in World War I. Hyūga supported Japanese forces in the early 1920s during the Siberian intervention in the Russian Civil War. In 1923, she assisted survivors of the Great Kantō earthquake. The ship was partially modernised in two stages in 1927–1928 and 1931–1932, during which her forward superstructure was rebuilt in the pagoda mast style. Hyūga was reconstructed in 1934–1936, improvements being made to her armour and propulsion machinery. Afterwards, she played a minor role in the Second Sino-Japanese War.
Despite the expensive reconstruction, the ship was considered obsolete by the eve of the Pacific War, and did not see significant action in the early years of the war. After the loss of most of the IJN's large aircraft carriers during the Battle of Midway in mid-1942, she was rebuilt with a flight deck replacing the rear pair of gun turrets to give her the ability to operate an air group of floatplanes; lack of aircraft and qualified pilots meant that Hyūga never operated her aircraft in combat. She participated in the Battle off Cape Engaño in late 1944, where she helped to decoy the American carrier fleet supporting the invasion of Leyte away from the landing beaches. Afterwards, the ship was transferred to Southeast Asia, occasionally serving as a flagship. In early 1945, Hyūga participated in Operation Kita, during which she transported petrol and other strategic materials back to Japan. The ship was then reduced to reserve until she was sunk during American airstrikes in July. After the war, Hyūga was scrapped in 1946–1947.
Design and description
thumb|upright=1.5|left|American ship-recognition drawing of the Ise-class battleships before their conversion
The Ise class was designed as an improved version of the preceding . The ships had a length of overall, a beam of and a draught of at deep load. They displaced at standard load and at deep load, roughly more than the earlier ships. Their crew consisted of 1,360 officers and ratings. their beam to and their draught to . Their displacement increased over to at deep load. The crew now numbered 1,376 officers and enlisted men. Each of the boilers consumed a mixture of coal and oil, and the ships carried enough of both to give them a range of at a speed of .
During their 1930s modernisation, the boilers on each ship were replaced by eight new Kampon oil-fired boilers. The ships' secondary armament consisted of twenty Type3 guns in single mounts. Eighteen of these were mounted in casemates in the forecastle and superstructure and the remaining pair were mounted on the deck above them and protected by gun shields. Anti-aircraft defence was provided by four 40-calibre 3rd Year Type 8-centimetre (3 in) anti-aircraft (AA) guns in single mounts. The ships were also fitted with six submerged torpedo tubes, three on each broadside.
In 1931–1933 the AA guns were replaced with eight Type 89 dual-purpose guns, placed beside the forward superstructure in four twin-gun mounts. Two twin-gun mounts for license-built Vickers two-pounder () light AA guns were also added while the pair of 14 cm guns on the upper deck were removed.
During the mid-1930s reconstruction, the torpedo tubes were removed, and the Vickers two-pounders were replaced by twenty license-built Hotchkiss Type 96 light AA guns in 10 twin-gun mounts. During the reconstruction, the forward pair of 14-centimetre guns in the forecastle were removed. The turrets were protected with an armour thickness of on the face and 76 mm on the roof. The casemate armour was thick and that of the barbettes was 299 mm thick rather than the originally planned 305 mm.
Construction and career
thumb|Hyūga shortly after completion
Hyūga, named after Hyūga Province, one of the traditional provinces of Japan, was laid down at the Mitsubishi Heavy Industries shipyard in Nagasaki on 6May 1915 and launched on 27 January 1917. Hyūga was then assigned to the 1st Battleship Division of the 1st Fleet. Captain Kinzaburo Mimura relieved Nakegawa on 10 November. An explosion in No.3 gun turret killed 11 crewmen and wounded another 25 during a gunnery exercise on 24 October 1919. Mimura was relieved in his turn by Captain Genjiro Katsuki on 20 November. Hyūga accidentally collided with and sank the schooner Hiromiya Maru, killing two of the sailing ship's crew, on 21 July 1920. On 29 August, the ship began the first of numerous patrols off the Siberian coast and in northern waters in support of Japan's Siberian Intervention against the Bolshevik Red Army. Captain Hidesaburo Ishikawa replaced Katsuki on 20 November and he was replaced by Captain Genji Ide on 20 November 1921. Hyūga, zigzagging at , took evasive action at the last minute and managed to avoid a direct collision with the stationary I-4, although Hyūga suffered minor damage to her hull plating when her bow grazed I-4′s hull. the division, reinforced by the battleships and and the light carrier , sortied from Hashirajima to the Bonin Islands as distant support for the 1st Air Fleet attacking Pearl Harbor, and returned six days later. Captain Chiaki Matsuda relieved Ishizaki on 20 February 1942. Together with the rest of the 2nd Battleship Division, Hyūga pursued but did not catch the American carrier force that had launched the Doolittle Raid on 18 April. Commanded by Vice-Admiral Shirō Takasu, the division was composed of Japan's four oldest battleships, including Hyūga, accompanied by two light cruisers, 12 destroyers, and two oilers. Official records do not show the division as part of the larger Midway operation, known as Operation AL; they were to accompany the fleet under Admiral Isoroku Yamamoto, but were only to provide support to the Aleutian task force if needed.
Conversion to a hybrid carrier
thumb|Ise after her 1944 reconstruction
The loss of four Japanese aircraft carriers during the Battle of Midway in June severely limited the ability of the IJN to conduct operations and alternatives were sought. Plans for full conversions of battleships into aircraft carriers were rejected on the grounds of expense and, most critically, time, so the IJN settled on removing the rear pair of turrets from the Ise-class ships and replacing them with a flight deck equipped with two rotating catapults. Matsuda was relieved by Captain Sueo Obayashi on 10 December and he was relieved in turn on 1May 1943, the same day that the conversion officially began. Work actually began two months later. The ship's air group was intended to consist of a dozen each Yokosuka D4Y Suisei dive bombers (Allied reporting name "Judy"), modified for catapult launching, and Aichi E16A reconnaissance floatplanes (Allied reporting name "Paul"), of which two to three of each were reserves. The former had to land either on a conventional carrier or on land bases, whereas the E16A could be hoisted back aboard using a crane, after landing on the water near the ship.
During the conversion, all of the 14 cm guns were removed and the ship's anti-aircraft suite was heavily reinforced. The eight 12.7 cm Type 89 guns were supplemented with four twin mounts and the existing 2.5 cm Type 96 AA twin-gun mounts were replaced by 19 triple-gun mounts for a total of 57 weapons.
These changes increased the ship's overall length to and the removal of the heavy gun turrets and their barbettes reduced her displacement to at deep load, despite the addition of more fuel oil storage. The extra fuel increased Hyūgas range to . The weight reductions decreased her draught to . The crew now numbered 1,463 officers and enlisted men. Two days later, Hyūga became the flagship of the Fourth Carrier Division, now commanded by the recently promoted Rear Admiral Matsuda. In September, six racks of 30-tube 12.7 cm anti-aircraft rocket launchers were added.
Battle off Cape Engaño and afterwards
thumb|Hyūga on her sea trials in November 1943 after her conversion
After the Americans began attacking Japanese installations in the Bonin Islands on 10 October 1944, the aircraft of the Fourth Carrier Division were ordered to prepare for combat by the commander of the Combined Fleet, Admiral Soemu Toyoda. Two days later, the 634th Naval Air Group was reassigned to the Second Air Fleet and began flying to bases in southern Kyushu; among these were nine D4Ys and a dozen E16As assigned to Ise and Hyūga. On 14 October they attacked the aircraft carriers of Task Force 38 near Formosa with little effect and heavy losses. The following day Nomura was promoted to rear admiral.
On the morning of 25 October, Hyūga was positioned near the light carriers and to protect them with her anti-aircraft guns. Her radar picked up the first of five American airstrikes at a range of at 07:13, but the battleship was not a primary target. Fragments from near misses by bombs damaged the ship's anti-torpedo blister and she developed a 5° list that was easily corrected. Despite Hyūgas protection, Chiyoda was set afire and her engines were disabled. Matsuda ordered the battleship and the light cruiser to tow the crippled carrier, but Hyūga was unable to do so and rejoined the main body at 18:30. The American submarine spotted the Fourth Carrier Division at 17:42 and manoeuvered to attack, missing with six torpedoes at 18:43. At 19:00 Ozawa ordered Matsuda to take his ships south to defend Isuzu and her escorting destroyers that were attempting to rescue Chiyodas survivors, despite gunfire from a group of four American cruisers. Unable to locate either group of ships, Ozawa ordered Matsuda to reverse course at 23:30 and head for Amami Ōshima to refuel. Despite being spotted by American submarines en route, the division arrived safely on 27 October. That same day Ozawa transferred his flag to Hyūga. After leaving the island the following day, they were unsuccessfully attacked by the submarine before their arrival at Kure on the 29th.