The were a pair of dreadnought battleships built for the Imperial Japanese Navy (IJN) during World War I. Both ships carried supplies for the survivors of the Great Kantō earthquake in 1923. They were modernized in 1934–1937 with improvements to their armour and machinery and a rebuilt superstructure in the pagoda mast style. Afterwards they played a minor role in the Second Sino-Japanese War.
Despite the expensive reconstructions, both vessels were considered obsolete by the eve of the Pacific War, and neither saw significant action in the early years of the war. Following the loss of most of the IJN's large aircraft carriers during the Battle of Midway in mid-1942, they were rebuilt with a flight deck replacing the rear pair of gun turrets to give them the ability to operate an air group of floatplanes. A lack of aircraft and qualified pilots, however, meant that they never actually operated their aircraft in combat. While awaiting their air group, the sister ships were occasionally used to ferry troops and material to Japanese bases. They participated in the Battle off Cape Engaño in late 1944, where they decoyed the American carrier fleet supporting the invasion of Leyte away from the landing beaches. Afterwards both ships were transferred to Southeast Asia; in early 1945 they participated in Operation Kita, where they transported petrol and other strategic materials to Japan. The sisters were then reduced to reserve until they were sunk during American airstrikes in July. After the war they were scrapped in 1946–1947.
Background
The design of the Ise-class battleships was shaped both by the ongoing international naval arms race and a desire among Japanese naval planners to maintain a fleet of capital ships powerful enough to defeat the United States Navy in an encounter in Japanese territorial waters.Stille, p. 4 The IJN's fleet of battleships had proven highly successful in 1905, the last year of the Russo-Japanese War, which culminated in the destruction of the Russian Second and Third Pacific Squadrons at the Battle of Tsushima.Evans & Peattie, p. 124
In the aftermath, the Japanese Empire immediately turned its focus to the two remaining rivals for imperial dominance in the Pacific Ocean: Britain and the United States. Satō Tetsutarō, a Japanese Navy admiral and military theorist, speculated that conflict would inevitably arise between Japan and at least one of its two main rivals. To that end, he called for the Japanese Navy to maintain a fleet with at least 70% as many capital ships as the US Navy.Evans & Peattie, p. 143 This ratio, Satō theorized, would enable the Imperial Japanese Navy to defeat the US Navy in one major battle in Japanese waters in any eventual conflict. Accordingly, the 1907 Imperial Defence Policy called for the construction of a battle fleet of eight modern battleships, each, and eight modern armoured cruisers, each.Evans & Peattie, p. 150 This was the genesis of the Eight-Eight Fleet Program, the development of a cohesive battle line of sixteen capital ships.Stille, p. 7
The launch of in 1906 by the Royal Navy raised the stakes,Evans & Peattie, p. 152 and complicated Japan's plans. Displacing and armed with ten guns, Dreadnought rendered all existing battleships obsolete by comparison.Sandler, p. 90 The launch of the battlecruiser the following year was a further setback for Japan's quest for parity.Evans & Peattie, p. 154 When the two new s and two armoured cruisers, launched by 1911, were outclassed by their British counterparts, the Eight-Eight Fleet Program was restarted.Evans & Peattie, p. 159
The first battleships built for the renewed Eight-Eight Fleet Program were the two dreadnoughts of the , ordered in 1907 and laid down in 1908. In 1910, the Navy put forward a request to the Diet (parliament) to secure funding for the entirety of the program at once. Because of economic constraints, only four battlecruisers and a single battleship of the Fusō class were ultimately approved by the Diet. Three more Fusō-class ships (, , and ) were approvedEvans & Peattie, pp. 159, 166 and all three were ordered in April 1913. While Yamashiro was laid down later that year, the IJN lacked the funding to proceed with the construction of Ise and Hyūga until the Diet authorized additional funding for the ships in July 1914.Lengerer 2011, pp. 13, 19
Design and description
The progress of Fusōs construction, while the IJN waited for the funding to be released and foreign developments, caused the IJN to reassess the Fusō-class design. The distribution of the midships gun turrets was the most obvious flaw as they complicated the protection of the midships magazine and exposed more of the ship to the blast effects of the guns when they fired. Another issue was that Japanese sailors had problems maintaining a high rate of fire with the shells used in the manually loaded secondary guns used in the Fusō class and earlier designs. To resolve this issue, the IJN designed a smaller gun that offset its lighter shell weight with a higher rate of fire. It also decided that the barbette armour of the earlier ships was too thin and wanted a modest increase in speed to partially counter the higher speeds of the latest foreign ships like the British s and Russian s. For financial reasons more powerful engines could not be ordered so the new design was lengthened slightly and the boiler rooms enlarged to increase speed by to . To save weight the forecastle deck was shortened so that the lower midships gun turret was lower than in the Fusō class. This reduced the crew's accommodations despite a significant increase in the crew's numbers and naval historian Fukui Shizuo believed that these ships had the worst habitability of any Japanese capital ship. The final design was designated A-92 by the IJN.Lengerer 2011, pp. 16–17, 19–20, 33–34
The ships had a length of overall, a beam of and a draught of at deep load.Lengerer March 2007, p. 9 They displaced at normal load and at deep load, roughly more than the preceding class. Their crew consisted of 1,360 officers and enlisted men.Jentschura, Jung & Mickel, pp. 25–26 They had a metacentric height of at deep load.Lengerer 2011, p. 40
During the ships' modernization during the 1930s, their forward superstructures were enlarged with multiple platforms added to their tripod foremasts. Both ships were also given torpedo bulges to improve their underwater protection and to compensate for the weight of the additional armour. In addition, their sterns were lengthened by . These changes increased their overall length to , their beam to and their draft to .Chesneau, p. 171 Their displacement increased over to at deep load.Lengerer 2009, p. 51 The crew now numbered 1,376 officers and enlisted men.
Propulsion The Ise-class ships had two sets of direct-drive steam turbines, each of which drove two propeller shafts with propellers. The high-pressure turbines drove the wing shafts while the low-pressure turbines drove the inner shafts. The turbines were designed to produce a total of (Hyūga and Ise respectively), using steam provided by 24 Kampon Ro Gō water-tube boilers at working pressures of . Both ships comfortably exceeded their designed speed of during their sea trials; Ise reached from and Hyūga exceeded that with from .Lengerer 2011, pp. 21–22 Each of the boilers consumed a mixture of coal and oil and the ships had a stowage capacity of of coal and of fuel oil, which gave them a range of at a speed of .Jentschura, Jung & Mickel, p. 26 Ise and Hyūga had three generators of capacity and two turbo generators at 225 volts.Lengerer March 2007, p. 8
During their 1930s modernization, the boilers on each ship were replaced by eight new Kampon oil-fired boilers, fitted into the former aft boiler room, and the forward funnel was removed. The turbines were replaced by four geared Kampon turbines with a designed output of intended to increase their speed to . On her trials, Ise reached a top speed of from . The fuel storage of the ships was increased to a total of of fuel oil that gave them a range of at a speed of .
Armament The twelve 45-calibre Type 41 guns of the Ise class were mounted in three pairs of twin-gun, superfiring turrets. Numbered one through six from front to rear, each turret weighed . The hydraulically powered turrets had an elevation capability of −5/+20 degrees. The guns had a rate of fire of 1.5–2 rounds per minute and could be loaded at any angle between −3 and +20 degrees. In 1921 the elevation was increased to +30 degrees and then to +43 degrees during their mid-1930s modernization,Lengerer 2011, pp. 24–26, 30 except for No. 6 turret as its supporting structure could not be lowered. The recoil mechanism of the guns was also changed from a hydraulic to a pneumatic system, which allowed for a faster firing cycle of the main guns.Lengerer March 2007, pp. 15–17
By World War II, the guns used Type 91 armour-piercing, capped shells. Each of these shells weighed and was fired at a muzzle velocity of . They had a maximum range of at +20 degrees of elevation and at +43 degrees after modernization. Also available was a high-explosive shell that had a muzzle velocity of . A special Type 3 Sanshikidan incendiary shrapnel shell was developed in the 1930s for anti-aircraft use.Campbell, pp. 175, 183
The ships' secondary armament consisted of twenty 50-calibre Type 3 guns. 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. They had a maximum elevation of +20 degrees which gave them a range of .Lengerer 2011, pp. 33–34 Each gun had a rate of fire of up to 10 rounds per minute.Campbell, p. 190 Anti-aircraft defence was provided by four 40-calibre 3rd Year Type 8-centimetre AA guns in single mounts. The high-angle guns had a maximum elevation of +75 degrees, and had a rate of fire of 13 to 20 rounds per minute. They fired a projectile with a muzzle velocity of to a maximum height of .Campbell, p. 198 The ships were also fitted with six submerged torpedo tubes, three on each broadside.Gardiner & Gray, p. 230 They carried twelve to eighteen 6th Year Type torpedoesLengerer 2011, p. 35 which had a warhead. They had three settings for range and speed: at , at , or at .Campbell, p. 204
In 1931–1933 the AA guns were replaced with eight 40-calibre Type 89 dual-purpose guns, fitted on both sides of the forward superstructures in four twin-gun mounts.Lengerer March 2007, p. 12 When firing at surface targets, the guns had a range of ; they had a ceiling of at their maximum elevation of +90 degrees. Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was around eight rounds per minute.Campbell, pp. 192–93 Two twin-gun mounts for license-built Vickers two-pounder () light AA guns were also added.Hackett, Kingsepp & Ahlberg, Ise and Hackett & Kingsepp, Hyūga These guns had a maximum elevation of +80 degrees and a rate of fire of 200 rounds per minute.Campbell, p. 74 The pair of 14 cm guns on the upper deck were removed at this time.