The were a pair of armored cruisers built for the Imperial Japanese Navy (IJN) in the late 1890s. As Japan lacked the industrial capacity to build such warships itself, the vessels were built in Britain. They were part of the "Six-Six Fleet" expansion program that began after the defeat of China during the First Sino-Japanese War of 1894–1895. The sister ships participated in three of the four main naval battles of the Russo-Japanese War of 1904–1905—the Battle of Port Arthur, the Battle off Ulsan and the Battle of Tsushima—but played a much more minor role in World War I.
Iwate was first used as a training ship in 1916 and remained in that role for most of the rest of her career. Her sister, Izumo, was mostly used for training during the 1920s, but became flagship of the IJN forces in China in 1932. She was involved in the Shanghai Incident that year and in the Second Sino-Japanese War that began five years later. The ship was used in the early stages of the Philippines Campaign during the Pacific War until she struck a mine at the end of 1941. Izumo joined her sister as a training ship in home waters in 1943. Both ships were sunk in a series of American air attacks on the naval base at Kure in July 1945. Their wrecks were refloated after the war and scrapped.
Background and design Japan initiated the 1896 Naval Expansion Plan after the First Sino-Japanese War of 1894–95. The plan included four armored cruisers and four battleships, all of which had to be ordered from foreign shipyards as Japan lacked the capability to build them itself. Further consideration of the Russian building program caused the IJN to believe that the battleships ordered under the original plan would not be sufficient to counter the Imperial Russian Navy. Budgetary limitations prevented ordering more battleships and the IJN decided to expand the number of more affordable armored cruisers to be ordered from four to six ships. The revised plan is commonly known as the "Six-Six Fleet".Evans & Peattie, pp. 57–62 These ships were purchased using the £30,000,000 indemnity paid by China after losing the First Sino-Japanese War.Brook 1999, p. 125 Unlike most of their contemporaries, which were designed for commerce raiding or to defend colonies and trade routes, the Izumo class was intended as fleet scouts and to be employed in the battleline.Milanovich, p. 72
Construction of the Izumo-class ships was awarded to the British shipbuilder Armstrong Whitworth of Elswick, the same shipyard that had built the earlier two armored cruisers of the "Six-Six Fleet".Brook 1999, pp. 112–13 They were also designed by Sir Philip Watts, who took advantage of rapidly advancing boiler technology to substitute lighter Belleville boilers in lieu of the cylindrical boilers of the earlier ships and used the weight saved to increase the thickness of the protective deck and improve the hull structure. The increased number of boilers required an extra funnel, which became the primary means of distinguishing between the two classes.Milanovich, pp. 74–76
Description
The Izumo-class ships were long overall and between perpendiculars. They had a beam of and had an average draft of . The ships displaced at normal load and at deep load. They had metacentric heights of .Milanovich, pp. 74, 80 Their crew consisted of 672 officers and enlisted men.Jentschura, Jung & Mickel, p. 74
The ships had two 4-cylinder triple-expansion steam engines, each driving a single propeller shaft.Milanovich, p. 81 Steam for the engines was provided by 24 Belleville boilers and the engines were rated at a total of . The sisters had a designed speed of and both exceeded it by at least a during their sea trials from . They carried up to of coalBrook 1999, p. 112 and could steam for at a speed of .
Armament
The main armament for all of the "Six-Six Fleet" armored cruisers was four Armstrong Whitworth-built 45-caliber guns in twin-gun turrets fore and aft of the superstructure. The electrically operated turrets were capable of 130° rotation left and right, and the guns could be elevated to +30° and depressed to −5°. Each turret accommodated 65 shells, but could only be reloaded through doors in the turret floor and the ship's deck that allowed the electric winch in the turret to hoist shells up from the shell room deep in the hull.Milanovich, pp. 76–77 The guns were manually loaded and had a rate of fire about 1.2 rounds per minute. The eight-inch gun fired armor-piercing (AP) projectiles at a muzzle velocity of to a range of .Milanovich, p. 78
The secondary armament consisted of fourteen Elswick Ordnance Company "Pattern Z" quick-firing (QF), 40-caliber, guns. All but four of these guns were mounted in armored casemates on the main and upper decks, and their mounts on the upper deck were protected by gun shields. Their AP shells were fired at a muzzle velocity of .Friedman, p. 276; Milanovich, p. 78 The ships were also equipped with a dozen 40-caliber QF 12-pounder () 12-cwt guns"Cwt" is the abbreviation for hundredweight, 12 cwt referring to the weight of the gun. and eight QF 2.5-pounder () Yamauchi guns as close-range defense against torpedo boats. The former gun fired three-inch, projectiles at a muzzle velocity of .Friedman, p. 114
The Izumo-class ships were equipped with four submerged torpedo tubes, two on each broadside. The Type 30 torpedo had a warhead and three range/speed settings: at , at or at .Milanovich, p. 80
Protection All of the "Six-Six Fleet" armored cruisers used the same armor scheme with some minor differences, one of which was that the four later ships all used Krupp cemented armor. The waterline belt ran the full length of the ships and its thickness varied from amidships to at the bow and stern. The thickest part of the belt covered the middle of the ship for a length of . It had a height of , of which was normally underwater. The upper strake of belt armor was thick and extended from the upper edge of the waterline belt to the main deck. It extended from the forward to the rear barbette. The Izumo class had oblique 5-inch armored bulkhead that closed off the ends of the central armored citadel.Milanovich, pp. 80–81
The barbettes, gun turrets and the front of the casemates were all 6 inches thick while the sides and rear of the casemates were protected by of armor. The deck was thick and the armor protecting the conning tower was in thickness.Chesneau & Kolesnik, p. 225 The ships had 30 watertight compartments in their double bottom and an additional 136 or 137 between the bottom and the upper deck.Milanovich, p. 80
Ships + Construction dataShipBuilder Laid downLaunchedCompleted Milanovich, p. 73FateArmstrong Whitworth, Elswick14 May 189819 September 189925 September 1900Sunk, 28 July 1945; broken up, 194711 November 189829 March 190018 March 1901Sunk, 25 July 1945; scrapped, 1946–1947
Service
Russo-Japanese War The sisters spent most of the Russo-Japanese War as flagships together in the 2nd Division of the 2nd Fleet; Iwate for the divisional commander, Rear Admiral Misu Sotarō, and Izumo for the fleet commander, Vice Admiral Kamimura Hikonojō.Kowner, pp. 241, 465 They participated in the Battle of Port Arthur on 9 February 1904, when Vice Admiral Tōgō Heihachirō led the Combined Fleet in an attack on the Russian ships of the Pacific Squadron anchored just outside Port Arthur. Tōgō had expected the earlier surprise night attack by his destroyers to be much more successful than it was, anticipating that the Russians would be badly disorganized and weakened, but they had recovered from their surprise and were ready for his attack. Iwate was moderately damaged by the Russians, but Izumo only slightly.Forczyk, pp. 42–43
In April 1904, the division was tasked to contain the Russian armored cruisers based at Vladivostok, but failed to do so until 13 August when the latter tried to rendezvous with the ships that attempted to breakout from Port Arthur. Unbeknownst to the Russians, Tōgō had defeated the ships from Port Arthur during the Battle of the Yellow Sea on 10 August and the Russian squadron from Vladivostok was intercepted off Ulsan, Korea by the 2nd Division. The steering of the Russian cruiser was damaged early in the battle and the Russians made several attempts to prevent the Japanese from concentrating fire on her, but were ultimately forced to abandon her to her fate. Kamimura left Rurik to the tender ministrations of his reinforcements and pursued the two remaining Russian ships for a time before breaking off pursuit prematurely based on an incorrect report that Izumo had expended most of her ammunition. That ship was hit over 20 times, but suffered fewer than 20 men killed or wounded. Iwate, in contrast, was hit far fewer times, but one of them started a major ammunition fire that killed or wounded dozens of men.Brook 2000, pp. 43, 45 After the battle, the sisters were refitted and assigned to different units, escorting troop convoys to northern Korea, providing cover while a minefield was laid off Vladivostok, and blockading the Tsugaru Strait until the Russian ships from the Baltic Fleet approached Japan in mid-1905.Corbett 1994, II, pp. 52, 104, 159–62, 176–77
Battle of Tsushima
The Russian 2nd and 3rd Pacific Squadrons were spotted on the morning on 27 May 1904 and Tōgō ordered his ships to put to sea. Izumo and Iwate had rejoined the 2nd Division in anticipation of this battle and Kamimura's ships confirmed the initial spotting later that morning before joining Tōgō's battleships. Together with most of the Japanese battleships, the division opened fire at 14:10 on the Russian battleship , which was forced to fall out of formation at 14:50 and sank 20 minutes later. After a failed torpedo attack was repulsed by Iwate and several other cruisers around the same time, the Russian battleship suddenly appeared out of the mist at 15:35 at short range. Kamimura's ships engaged her for five minutes before she disappeared back into the mists. Later in the day, Kamimura led his division in a fruitless pursuit of some of the Russian cruisers around 17:30. He abandoned his chase around 18:03 and encountered the Russian battleline about a half hour later. He stayed at long range and his ships fired when practicable before ceasing fire at 19:30.Campbell 1978, Part 2, pp. 128–32; Part 3, pp. 186–87
The surviving Russian ships were spotted the next morning and the Japanese ships opened fire and stayed beyond the range at which the Russian ships could effectively reply. Rear Admiral Nikolai Nebogatov therefore decided to surrender his ships as he could neither return fire nor close the range.Corbett 1994, II, pp. 319–20 Well after Nebogatov's surrender, the coast defense ship was spotted well south of Nebogatov's ships and Iwate and the armored cruiser, , were tasked to pursue her. The Japanese ships demanded that the Russians surrender when they came within range, but her captain refused. Admiral Ushakov attempted to close the range to bring the Japanese cruisers within range of her guns, but they were fast enough to keep the range open and the Russian ship could not hit either of them. After about half an hour, Admiral Ushakov had been heavily damaged to bear and her commander ordered his crew to abandon ship and the scuttling charges detonated. Both Iwate and Izumo were struck several times during the battle, but neither was significantly damaged and casualties were light.Brook 1999, p. 113; Campbell 1978, Part 4, p. 263 After the battle, the division covered amphibious landings in northeastern Korea in July and August before the war ended.Corbett, II, pp. 356, 363–65, 377–80
Subsequent service