Izumo-class cruiser

Izumo-class cruisers

Company type	Armored cruisers
Industry	Naval shipbuilding
Founded	Late 1890s
Founder	Armstrong Whitworth (builder)
Headquarters	Elswick , United Kingdom
Products	Warships (armored cruisers)

Overview

The Izumo-class cruisers (出雲型装甲巡洋艦, Izumo-gata sōkōjun'yōkan) consisted of two armored cruisers constructed for the Imperial Japanese Navy (IJN) during the late 1890s. Due to Japan's limited industrial capabilities at the time, these warships were manufactured in the United Kingdom. They formed part of the expansion initiative known as the "Six-Six Fleet", which was launched following Japan’s victory over China in the First Sino-Japanese War of 1894–1895. Throughout the Russo-Japanese War of 1904–1905, the two sister ships took part in three of the four significant naval engagements: the Battle of Port Arthur, the Battle off Ulsan, and the Battle of Tsushima. However, their involvement in World War I was considerably less prominent.

The cruiser Iwate transitioned to a training ship role in 1916 and maintained this function for much of her remaining service life. Meanwhile, her sister ship, Izumo, primarily served as a training vessel throughout the 1920s before being appointed flagship of IJN forces stationed in China in 1932. During that year, she played a role in the Shanghai Incident and later participated in operations during the Second Sino-Japanese War, which commenced five years afterward. In the early phase of the Philippines Campaign amid the Pacific War, Izumo was active until she struck a mine at the end of 1941. Subsequently, she returned to training duties within Japanese home waters by 1943 alongside Iwate. Both cruisers met their demise during a series of American air raids targeting the naval base at Kure in July 1945. Following the war, their hulls were salvaged and ultimately dismantled for scrap.

Background and design

Following the First Sino-Japanese War of 1894–95, Japan launched the 1896 Naval Expansion Plan. This initiative called for the acquisition of four armored cruisers alongside four battleships, all of which had to be procured from foreign shipyards due to Japan's lack of domestic construction capabilities. The Imperial Japanese Navy (IJN), upon evaluating Russia's naval development, concluded that the battleships initially ordered would be inadequate to effectively counter the Imperial Russian Navy. Financial constraints prevented increasing the number of battleships, so the IJN opted to raise the count of more cost-effective armored cruisers from four to six vessels. This updated strategy became widely known as the "Six-Six Fleet". Funding for these ships came from the £30,000,000 indemnity paid by China after its defeat in the First Sino-Japanese War. Unlike many contemporaneous cruisers designed primarily for commerce raiding or colonial defense, the Izumo class was created to serve as fleet scouts and participate directly in the battleline.

The contract for constructing the Izumo-class vessels was awarded to Armstrong Whitworth, a British shipbuilding firm based in Elswick, which had previously built the two Asama-class armored cruisers of the "Six-Six Fleet". Sir Philip Watts was responsible for their design, incorporating advancements in boiler technology by replacing earlier cylindrical boilers with lighter Belleville boilers. This weight reduction allowed for thicker protective deck armor and reinforced hull structures. The need for additional boilers led to an extra funnel, which became a key distinguishing feature between this class and its predecessors.

Description

Left plan, elevation and half section of the Izumo class from Jane's Fighting Ships, 1904

The Izumo-class cruisers measured 132.28 meters (434 ft 0 in) in overall length and 121.92 meters (400 ft 0 in) between perpendiculars. Their beam spanned 20.94 meters (68 ft 8 in), with an average draft ranging between 7.21 to 7.26 meters (23 ft 8 in to 23 ft 10 in). These ships displaced between 9,423 to 9,503 metric tons (9,274 to 9,353 long tons) under normal load conditions and between 10,235 to 10,305 metric tons (10,073 to 10,142 long tons) when fully loaded. Their metacentric height varied from 0.73 to 0.88 meters (2 ft 5 in to 2 ft 11 in). The complement consisted of 672 officers and enlisted personnel.

Propulsion was provided by two 4-cylinder triple-expansion steam engines, each connected to a single propeller shaft. Power was generated by 24 Belleville boilers, producing a combined output rated at 14,500 indicated horsepower (10,800 kW). Designed to reach speeds of 20.75 knots (38.43 km/h; 23.88 mph), both vessels surpassed this during sea trials by over 1 knot (1.9 km/h; 1.2 mph), achieving power outputs between 15,739 to 16,078 ihp (11,737 to 11,989 kW). They could carry up to 1,551 metric tons (1,527 long tons) of coal, enabling a cruising range of approximately 7,000 nautical miles (13,000 km; 8,100 mi) at a speed of 10 knots (19 km/h; 12 mph).

Armament

Cross-sectional view of the eight-inch gun turret installed on all armored cruisers of the "Six-Six Fleet"

The primary firepower for every armored cruiser in the "Six-Six Fleet" consisted of four 45-caliber eight-inch (203 mm) guns manufactured by Armstrong Whitworth. These were arranged in twin gun turrets positioned at the fore and aft sections of the superstructure. Each turret was electrically driven, allowing a rotation of 130° to either side, with gun elevation ranging from −5° depression to +30° elevation. Turrets held up to 65 shells each, but reloading was only possible via hatchways in the turret floor and ship's deck, through which an electric winch lifted ammunition from the shell room deep within the hull. Loading was performed manually, with a firing rate near 1.2 rounds per minute. The eight-inch artillery discharged armor-piercing projectiles weighing 250-pound (113.5 kg) at a muzzle velocity of approximately 2,500 feet per second (760 m/s), reaching targets up to 20,000 yards (18,000 m) away.

Crew operating six-inch guns

The secondary battery comprised fourteen Elswick Ordnance Company "Pattern Z" quick-firing (QF), 40-caliber six-inch (152 mm) guns. Except for four units, these were installed within armored casemates located on the main and upper decks; those on the upper deck featured additional protection from gun shields. Their armor-piercing shells weighed approximately 100-pound (45.4 kg), propelled at a muzzle speed near 2,300 feet per second (700 m/s). Additionally, the vessels carried twelve 40-caliber QF 12-pounder (3 in (76 mm)) 12-cwt guns as well as eight QF 2.5-pounder (1.5 in (38 mm)) Hotchkiss Yamauchi guns intended for close-in defense against torpedo boats. The former fired three-inch projectiles weighing around 12.5-pound (5.7 kg) at a muzzle velocity of about 2,359 feet per second (719 m/s).

Each ship in the Izumo class was outfitted with four submerged torpedo tubes measuring 18.0-inch (457 mm), split evenly with two on each broadside. The Type 30 torpedo carried a warhead weighing roughly 100-kilogram (220 lb) and offered three operational range and speed configurations: 870 yards (800 m) at 27 knots (50 km/h; 31 mph), 1,100 yards (1,000 m) at 23.6 knots (43.7 km/h; 27.2 mph), or 3,300 yards (3,000 m) at a speed of 14.2 knots (26.3 km/h; 16.3 mph).

Protection

The armored cruisers of the "Six-Six Fleet" shared a largely uniform armor design, with slight variations among them. Notably, the four vessels constructed later were equipped with Krupp cemented armor. The waterline belt extended along the entire ship length, featuring thicknesses ranging from 7.0 inches (178 mm) amidships to 3.5 inches (89 mm) at both the bow and stern. The belt's thickest section spanned the central portion of the ship, measuring 275 feet 2 inches (83.87 m) in length. Its vertical dimension was 7 feet 0 inches (2.13 m), with approximately 4 feet 4 inches to 4 feet 7 inches (1.33 to 1.39 m) typically submerged beneath the waterline. Above this, an upper strake of belt armor, 5.0 inches (127 mm) thick, stretched from the waterline belt's top edge up to the main deck, covering a distance between 167 feet 11 inches to 174 feet 11 inches (51.18 to 53.31 m) from the forward to aft barbette. The Izumo class incorporated angled 5-inch armored bulkheads sealing off the ends of the central armored citadel.

The barbettes, gun turrets, and forward faces of the casemates were all protected by 6 inches of armor, while the sides and rear sections of the casemates had armor thickness of 51 millimeters (2.0 in). Deck plating measured 63 millimeters (2.5 in) in thickness, and the conning tower boasted armor up to 356 millimeters (14.0 in) thick. The vessels featured 30 watertight compartments within their double bottom, supplemented by an additional 136 or 137 compartments situated between the bottom and upper deck.

Ships

Construction details

Ship	Builder	Laid down	Launched	Completed	Fate
Izumo	Armstrong Whitworth, Elswick	14 May 1898	19 September 1899	25 September 1900	Sunk on 28 July 1945; dismantled in 1947
Iwate		11 November 1898	29 March 1900	18 March 1901	Sunk on 25 July 1945; scrapped during 1946–1947

Russo-Japanese War

During most of the Russo-Japanese War, these sister ships served as flagships jointly within the 2nd Division of the 2nd Fleet; Iwate carried the divisional commander Rear Admiral Misu Sotarō, while Izumo was assigned to fleet commander Vice Admiral Kamimura Hikonojō. They took part in the Battle of Port Arthur on 9 February 1904, when Vice Admiral Tōgō Heihachirō led the Combined Fleet in an offensive against Russian vessels anchored just outside Lüshunkou District. Tōgō had anticipated that his destroyers’ earlier surprise nighttime assault would severely disrupt and weaken Russian defenses; however, the Russians quickly recovered and were prepared for his subsequent attack. During this engagement, Iwate sustained moderate damage from Russian fire, whereas Izumo was only lightly affected.

In April 1904, their mission was to contain Russian armored cruisers based in Vladivostok, though success was not achieved until 13 August when those Russian ships attempted to join forces with vessels escaping Port Arthur. Unaware that Tōgō had already defeated Port Arthur’s breakout fleet at the Battle of the Yellow Sea on 10 August, the Vladivostok squadron was intercepted off Ulsan, Korea by the Japanese 2nd Division. Early in this clash, damage to the steering gear of the Russian cruiser Rurik occurred. Despite several Russian efforts to shield her from concentrated Japanese fire, they ultimately had to abandon her. Kamimura left Rurik under care of reinforcements and briefly pursued two remaining Russian ships before ceasing pursuit prematurely due to an erroneous report that Izumo had nearly exhausted her ammunition supply. Although Izumo was struck over twenty times during combat, casualties remained under twenty killed or wounded. Conversely, Iwate received fewer hits but suffered a severe ammunition fire resulting in dozens of casualties.

Following this battle, both cruisers underwent refits and were reassigned: escorting troop convoys heading to northern Korea, supporting minefield deployment off Vladivostok, and enforcing a blockade of the Tsugaru Strait until mid-1905 when ships from the Russian Baltic Fleet neared Japanese waters.

Battle of Tsushima

Main article: Battle of Tsushima

On the morning of 27 May 1904, the Russian 2nd and 3rd Pacific Squadrons were detected, prompting Admiral Tōgō to command his fleet to set sail. The cruisers Izumo and Iwate had rejoined the 2nd Division in preparation for the impending engagement, and Kamimura's vessels later confirmed the initial sighting before linking up with Tōgō's battleships. At 14:10, most of the Japanese battleships, alongside this division, commenced firing on the Russian battleship Oslyabya, which was compelled to leave formation by 14:50 and sank approximately twenty minutes later. Around this time, a torpedo assault was thwarted by Iwate and several other cruisers. At 15:35, the Russian battleship Knyaz Suvorov suddenly emerged from the fog at close range, engaging Kamimura's ships for five minutes before vanishing into the mist again. Later that afternoon, Kamimura led his division in an unsuccessful pursuit of some Russian cruisers around 17:30, abandoning the chase by 18:03. About thirty minutes afterward, he encountered the Russian battleline but maintained a distant position, firing when opportunities arose before ceasing fire at 19:30.

A Japanese postcard depicting Izumo at anchor in 1905

The following morning, remaining Russian vessels were located, and Japanese forces opened fire while staying outside effective Russian firing range. Rear Admiral Nikolai Nebogatov, recognizing his inability to retaliate or close distance, chose to surrender his fleet. After Nebogatov’s capitulation, the coast defense ship Admiral Ushakov was sighted well south of Nebogatov’s group. The armored cruiser Yakumo and Iwate were assigned to intercept her. Upon closing range, they demanded surrender; however, her captain declined. Admiral Ushakov attempted to reduce the distance to bring her guns within effective range against the Japanese cruisers, but their superior speed allowed them to maintain distance and avoid hits. After approximately thirty minutes of engagement, with significant damage sustained, her commander ordered evacuation and initiated scuttling charges. During this battle, both Iwate and Izumo received several hits but suffered minimal damage and only light casualties. Following the conflict, the division provided cover for amphibious operations in northeastern Korea during July and August until hostilities concluded.

Subsequent service

During the Mexican Revolution, Izumo was deployed to patrol Mexico’s western coastline to protect Japanese nationals and interests, remaining there when Japan entered war against the German Empire on 23 August 1914. Her mission then shifted to locating German commerce raiders and safeguarding Allied maritime traffic along North and Central America’s Pacific coasts. In early 1915, she aided the armored cruiser Asama after it ran aground on rocks near Baja California. By 1917, Izumo had become flagship of Japan’s Mediterranean squadron. After World War I ended, she voyaged to Great Britain to take custody of former German submarines and escorted them partway back to Japan.

Meanwhile, Iwate contributed modestly during the war; she participated in the Battle of Tsingtao and subsequently patrolled the South Sea Islands in search of German commerce raiders. Beginning in 1916 and continuing until late 1939, she undertook numerous training cruises for cadets from the Imperial Japanese Navy Academy. Similarly, Izumo commenced her own training voyages during the following decade.

Izumo anchored in Burrard Inlet near Vancouver, Canada in February 1925

In a modernization effort during 1924, four of their twelve-pounder guns were removed along with all QF 2.5-pounder weapons; a single anti-aircraft gun—a 40-caliber 8 cm/40 3rd Year Type naval gun—was installed. This AA gun could elevate up to +75 degrees and fired a three-inch (12.5 lb (5.67 kg)) shell at a muzzle velocity of 2,200 ft/s (680 m/s), reaching altitudes up to 23,600 feet (7,200 m). A further refit between 1930 and 1931 saw removal of torpedo tubes as well as all main deck six-inch guns; their casemates were sealed off leaving only four twelve-pounders aboard. During this period, Iwate received six new water-tube boilers replacing her original boilers; however, Izumo did not undergo reboilering until 1935. The updated boilers generated less steam pressure which limited engine output to 7,000 ihp (5,200 kW) and reduced maximum speed to 16 knots (30 km/h; 18 mph).

Service in China and World War II

Izumo anchored in the Huangpu River, Shanghai, 1932. To the left is the American armored cruiser USS Rochester.

In 1932, amid the First Shanghai Incident, Izumo was designated flagship of the newly reinstated 3rd Fleet, responsible for garrisoning Japanese-occupied territories in China. Two years later, she underwent modifications at the Sasebo Naval Arsenal to operate a floatplane. During the Second Sino-Japanese War, Izumo took part in the mid-1937 Battle of Shanghai, delivering naval gunfire support to Japanese ground forces.

At the onset of the Pacific War on 8 December 1941, Izumo was still stationed in Shanghai. She captured the American river gunboat USS Wake and participated in sinking the British river gunboat HMS Peterel. On 31 December, while supporting operations during the Philippines Campaign, she struck a mine in Lingayen Gulf. Meanwhile, her sister ship Iwate continued serving as a training vessel within home waters. Both cruisers were briefly reclassified as first-class cruisers on 1 July 1942 before being reassigned as training ships in 1943. Later that year, Izumo returned to Japan and joined Iwate in training naval cadets.

In early 1945, both ships underwent rearmament; their original 8-inch guns were replaced by four twin-mounted 12.7 cm (5.0 in) Type 89 dual-purpose guns, and half of their remaining 6-inch artillery was removed. The Type 89 guns had a maximum range of 16,100 yards (14,700 m) against surface targets and could reach an altitude ceiling of 30,970 feet (9,440 m) at +90 degrees elevation. Their maximum firing rate was fourteen rounds per minute, with a sustained rate near eight rounds per minute. Their light anti-aircraft defenses were considerably enhanced by installing nine (on Iwate) and fourteen (on Izumo) license-built Hotchkiss 25-millimeter Type 96 light AA guns arranged in single, double, and triple mounts, along with two single-mounted 13.2-millimeter Hotchkiss machine guns. Although the 25 mm (0.98 in) Type 96 was Japan’s standard light anti-aircraft weapon during World War II, it suffered from significant design flaws that limited its effectiveness. The twin and triple mounts lacked rapid train and elevation capabilities; targeting fast-moving aircraft was hindered by inadequate sights; the guns experienced excessive vibration; magazines were undersized; and they generated a strong muzzle blast. While their maximum range extended to 24,600 feet (7,500 m), their effective operational range was roughly between 4,900–9,800 feet (1,500–3,000 m).

During the American aerial raid on Kure in July 1945, both vessels were targeted but remained unscathed by direct hits. Nevertheless, shockwaves from nearby explosions caused severe flooding aboard both ships. On 25 July, Iwate sank in shallow waters, followed by Izumo, which capsized three days later. Both ships were officially struck from the navy list on 20 November; their wrecks were subsequently raised and dismantled during 1946–47.

References

• Brook, Peter (2000). "Armoured Cruiser vs. Armoured Cruiser: Ulsan 14 August 1904". In Preston, Antony (ed.). Warship 2000–2001. London: Conway Maritime Press. ISBN 0-85177-791-0.
• Brook, Peter (1999). Warships for Export: Armstrong Warships 1867–1927. Gravesend: World Ship Society. ISBN 0-905617-89-4.
• Campbell, John (1985). Naval Weapons of World War II. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-459-4.
• Campbell, N.J.M. (1978). "The Battle of Tsu-Shima, Parts 2, 3 and 4". In Preston, Antony (ed.). Warship. Vol. II. London: Conway Maritime Press. pp. 127–35, 186–192, 258–65. ISBN 0-87021-976-6.
• Chesneau, Roger, ed. (1980). Conway's All the World's Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN 0-85177-146-7.
• Chesneau, Roger; Kolesnik, Eugene M., eds. (1979). Conway's All the World's Fighting Ships 1860–1905. Greenwich: Conway Maritime Press. ISBN 0-8317-0302-4.
• Corbett, Julian Stafford (1994). Maritime Operations in the Russo-Japanese War, 1904–1905. Annapolis, Maryland: Naval Institute Press. ISBN 1-55750-129-7.
• Corbett, Julian (March 1997). Naval Operations to the Battle of the Falklands. History of the Great War: Based on Official Documents. Vol. I (2nd, reprint of the 1938 edition ed.). London and Nashville, Tennessee: Imperial War Museum and Battery Press. ISBN 0-89839-256-X. {{cite book}}: |edition= has extra text (help)
• Estes, Donald H. (1978). "Asama Gunkan: The Reappraisal of a War Scare". Journal of San Diego History. 24 (3). Archived from the original on 3 April 2016. Retrieved 11 May 2015.
• Evans, David; Peattie, Mark R. (1997). Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887–1941. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-192-7.
• Forczyk, Robert (2009). Russian Battleship vs Japanese Battleship, Yellow Sea 1904–05. Botley, UK: Osprey. ISBN 978-1-84603-330-8.
• Friedman, Norman (2011). Naval Weapons of World War One. Barnsley, South Yorkshire, UK: Seaforth. ISBN 978-1-84832-100-7.
• Fukui, Shizuo (1991). Japanese Naval Vessels at the End of World War II. London: Greenhill Books. ISBN 1-85367-125-8.
• Gardiner, Robert; Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 0-85177-245-5.
• Hackett, Bob; Kingsepp, Sander (2012). ""IJN Iwate: Tabular Record of Movement"". SOKO-JUNYOKAN - Ex-Armored Cruisers. Combinedfleet.com. Retrieved 23 April 2015.
• Hackett, Bob; Kingsepp, Sander (2014). ""IJN Izumo: Tabular Record of Movement"". SOKO-JUNYOKAN - Ex-Armored Cruisers. Combinedfleet.com. Retrieved 23 April 2015.
• Harmsen, Peter (2013). Shanghai 1937: Stalingrad on the Yangtze. Havertown, Pennsylvania: Casemate. ISBN 978-1-61200-167-8.