The were a pair of large
armored cruiser
The armored cruiser was a type of warship of the late 19th and early 20th centuries. It was designed like other types of cruisers to operate as a long-range, independent warship, capable of defeating any ship apart from a battleship and fast en ...
s (''Sōkō jun'yōkan'') built for the
Imperial Japanese Navy
The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender ...
(IJN) in the first decade of the 20th century. Construction began during the
Russo-Japanese War
The Russo-Japanese War ( ja, 日露戦争, Nichiro sensō, Japanese-Russian War; russian: Ру́сско-япóнская войнá, Rússko-yapónskaya voyná) was fought between the Empire of Japan and the Russian Empire during 1904 and 1 ...
of 1904–05 and their design was influenced by the IJN's experiences during the war. The British development of the
battlecruiser
The battlecruiser (also written as battle cruiser or battle-cruiser) was a type of capital ship of the first half of the 20th century. These were similar in displacement, armament and cost to battleships, but differed in form and balance of at ...
the year after was completed made her and her
sister ship
A sister ship is a ship of the same class or of virtually identical design to another ship. Such vessels share a nearly identical hull and superstructure layout, similar size, and roughly comparable features and equipment. They often share a ...
obsolete, as they were slower and more weakly armed than the British, and later German, ships. Despite this, they were reclassified in 1912 as battlecruisers by the IJN.
Both ships played a small role in
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
as they unsuccessfully hunted for the
German East Asia Squadron in late 1914. They became
training ship
A training ship is a ship used to train students as sailors. The term is mostly used to describe ships employed by navies to train future officers. Essentially there are two types: those used for training at sea and old hulks used to house classr ...
s later in the war. ''Tsukuba'' was destroyed in an accidental
magazine explosion in 1917 and subsequently
scrapped. Her sister was disarmed in 1922 in accordance with the terms of the
Washington Naval Treaty and broken up for scrap in 1924.
Background

About a month after the Russo-Japanese War began in February 1904, the
Japanese Diet authorized a temporary special budget of
¥48,465,631 that would last until the end of the war. It included the 1904 War Naval Supplementary Program which authorized construction of two
battleships and four armored cruisers, among other ships. Two of the latter became the ''Tsukuba''-class cruisers which were ordered on 23 June.
Based on the experience at the
Battle of the Yellow Sea
The Battle of the Yellow Sea ( ja, 黄海海戦, Kōkai kaisen; russian: Бой в Жёлтом море) was a major naval battle of the Russo-Japanese War, fought on 10 August 1904. In the Russian Navy, it was referred to as the Battle of 10 ...
in August 1904 where the Russians opened fire at ranges well beyond what had been anticipated before the war, the IJN decided to arm the ships with 45-calibre (45 feet long barrel) guns, which outranged the
12" 40-calibre guns used by the Japanese battleships in the war.
[ The increase in armament was also justified by a change in the IJN's doctrine for these ships in which they were now intended to participate in the line of battle and overpower the enemy's screening armored cruisers.][Itani, Lengerer & Rehm-Takahara, p. 55] The ''Tsukuba''s were "briefly the world's most powerful cruisers in service until the completion of the first true battlecruisers, the British ". They were also the first capital ship
The capital ships of a navy are its most important warships; they are generally the larger ships when compared to other warships in their respective fleet. A capital ship is generally a leading or a primary ship in a naval fleet.
Strategic i ...
s to be designed and constructed entirely by Japan in a Japanese shipyard.[
This type of warships with speed of a cruiser and the firepower and protection armor of a battleship was advocated by First Sea Lord Jacky Fisher who coined the term 'battlecruiser' for the type in the UK later in 1908.
]
Design and description
The ''Tsukuba''-class design was very similar to that of the British armored cruiser, albeit some larger. The Japanese ships were shorter and beamier, but shape of the hull and the positioning of the armament was almost identical, although the traditional ram bow was replaced by a clipper-style bow. The adoption of more powerful Miyabara water-tube boilers by the IJN allowed the number of boilers to be reduced from 30 in the British ships to 20 in the ''Tsukuba''-class ships with no loss of power or speed. This reduced the length required for their propulsion machinery and allowed the larger guns and their ammunition to be accommodated.
The ''Tsukuba''s had an overall length of and a length between perpendiculars of , a beam of , and a normal draft of about . They displaced at normal load[Itani, Lengerer & Rehm-Takahara, p. 54] and at full load.[Jentschura, Jung & Mickel, p. 77] They had a metacentric height of which made them bad gun platforms as they had a very quick roll. The crew numbered about 820 officers and enlisted men.[
The ''Tsukuba''-class ships had two 4-cylinder vertical triple-expansion steam engines, each driving a single ]propeller shaft
A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power and torque and rotation, usually used to connect ...
. Steam for the engines was provided by 20 Miyabara boilers with a working pressure of .[Itani, Lengerer & Rehm-Takahara, p. 73] The engines were rated at a total of to give a designed speed of . During their sea trials the ships reached from .[ The ''Tsukuba''s were first ships of the IJN to use ]fuel oil
Fuel oil is any of various fractions obtained from the distillation of petroleum (crude oil). Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil, marine fuel oil (MFO), bu ...
sprayed onto the coal for extra power[ and carried up to of coal and of oil.][
]
Armament
The ''Tsukuba''-class armored cruisers were armed with four 45- caliber 12-inch 41st Year Type guns. The guns were mounted in twin-gun hydraulically powered centerline turrets, one each fore and aft of the superstructure
A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships.
Aboard ships and large boats
On water craft, the superstruct ...
. The guns had an elevation range of −3° to +23° and normally loaded their rounds at an angle of +5°, although loading at any angle up to +13° was theoretically possible. They fired projectiles at a muzzle velocity of ; this provided a maximum range of with armor-piercing (AP) shells. Their secondary armament
Secondary armament is a term used to refer to smaller, faster-firing weapons that were typically effective at a shorter range than the main (heavy) weapons on military systems, including battleship- and cruiser-type warships, tanks/armored ...
consisted of a dozen Elswick Ordnance Company "Pattern GG" 45-caliber guns mounted in armored casemate
A casemate is a fortified gun emplacement or armored structure from which guns are fired, in a fortification, warship, or armoured fighting vehicle.Webster's New Collegiate Dictionary
When referring to antiquity, the term "casemate wall" mean ...
s on the middle and main decks. The eight guns on the middle deck were very close to the waterline
The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that ind ...
and could not be used in bad weather.[Itani, Lengerer & Rehm-Takahara, p. 68] Their AP shells were fired at a muzzle velocity of .
Close-range defense against torpedo boat
A torpedo boat is a relatively small and fast naval ship designed to carry torpedoes into battle. The first designs were steam-powered craft dedicated to ramming enemy ships with explosive spar torpedoes. Later evolutions launched variants of s ...
s consisted of twelve quick-firing (QF) 4.7-inch 41st Year Type guns. Four of these were mounted in casemates in the bow and stern, while the remaining guns were positioned on the upper deck and protected by gun shields.[Itani, Lengerer & Rehm-Takahara, p. 71] These guns fired AP shells at a muzzle velocity of . The ships were also equipped with four 40-caliber QF 12-pounder 12-cwt guns.["Cwt" is the abbreviation for hundredweight, 12 cwt referring to the weight of the gun.] The gun fired projectiles at a muzzle velocity of . The ''Tsukuba''-class ships were equipped with three submerged torpedo tube
A torpedo tube is a cylindrical device for launching torpedoes.
There are two main types of torpedo tube: underwater tubes fitted to submarines and some surface ships, and deck-mounted units (also referred to as torpedo launchers) installed abo ...
s, one on each broadside, and one in the stern
The stern is the back or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite the bow, the foremost part of a ship. Ori ...
. All of the tubes in ''Tsukuba'', and the stern tube in ''Ikoma'', were in diameter. The broadside tubes in ''Ikoma'', however, were in size.[
]
Armor
In order to keep the displacement down and the speed the same as in the earlier armored cruisers, armor in the ''Tsukuba'' class was about the same in thickness, although in an improved layout. The waterline armor belt of Krupp cemented armor was thick between the 12-inch gun turrets although it was only thick fore and aft of the turrets. Above it was a strake of armor that extended between the barbette
Barbettes are several types of gun emplacement in terrestrial fortifications or on naval ships.
In recent naval usage, a barbette is a protective circular armour support for a heavy gun turret. This evolved from earlier forms of gun protectio ...
s and protected the 6-inch casemates. The aft ends of the main armor belt were connected to the main gun barbette
Barbettes are several types of gun emplacement in terrestrial fortifications or on naval ships.
In recent naval usage, a barbette is a protective circular armour support for a heavy gun turret. This evolved from earlier forms of gun protectio ...
s by transverse bulkheads. The lack of a forward bulkhead and the thinness of the aft bulkhead were serious weaknesses in the ships' protection.
The front of the main gun turrets were protected by armor plates thick, the sides by plates and they had a roof. The main barbettes were protected by seven inches of armour. The thickness of the armored decks ranged in thickness from 1.5 inches on the flat and at the ends of the ship to on the slope of the deck. The sides of the forward conning tower were thick and it had a 3-inch roof.
Ships in class
Construction and service
The Yokosuka Naval Arsenal had the most experience in building warships, but the IJN feared a bombardment by the Russian 2nd and 3rd Pacific Squadrons then en route from the Baltic Sea
The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain.
The sea stretches from 53°N to 66°N latitude and fr ...
and decided to build the ''Tsukuba''s at the less-exposed Kure Naval Arsenal, even though Kure's experience was with ship repair and conversions. This meant that skilled workers had to be brought from Yokosuka to train the workforce at Kure in construction techniques. ''Tsukuba'' was laid down after the newly constructed Slipway
A slipway, also known as boat ramp or launch or boat deployer, is a ramp on the shore by which ships or boats can be moved to and from the water. They are used for building and repairing ships and boats, and for launching and retrieving small ...
No. 3 was completed in November 1904 and ''Ikoma'' followed once the extension of Slipway No. 2 was finished. These ships were over three times larger than the biggest ship previously built in Japan, the protected cruiser
Protected cruisers, a type of naval cruiser of the late-19th century, gained their description because an armoured deck offered protection for vital machine-spaces from fragments caused by shells exploding above them. Protected cruisers r ...
. Priority of effort was given to the building of ''Tsukuba'' and she was completed in a very creditable two years. ''Ikoma'' took an additional year to finish as the end of the war shortly after she was laid down reduced the pressure to complete her as fast as possible. In addition, her slipway initially lacked any cranes
Crane or cranes may refer to:
Common meanings
* Crane (bird), a large, long-necked bird
* Crane (machine), industrial machinery for lifting
** Crane (rail), a crane suited for use on railroads
People and fictional characters
* Crane (surname), ...
or derrick
A derrick is a lifting device composed at minimum of one guyed mast, as in a gin pole, which may be articulated over a load by adjusting its guys. Most derricks have at least two components, either a guyed mast or self-supporting tower, an ...
s to lift heavy material until electrically powered steel shearleg derricks were improvised. Construction of both ships was somewhat delayed by difficulties in procuring enough steel plates and rivet
A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the ''tail''. On installation, the rivet is placed in a punched ...
s; quantities of both had to be imported from the United States.
Possibly due to the speed at which she was constructed, ''Tsukuba'' reportedly suffered from numerous defects.[ Shortly after she was completed, the ship sailed for America where she participated in the Jamestown Exposition Naval Review in May–June 1907. The ship then sailed to Europe where she made numerous port visits over the next several months. While in Britain, ''Tsukuba'' was fitted with a ]Vickers
Vickers was a British engineering company that existed from 1828 until 1999. It was formed in Sheffield as a steel foundry by Edward Vickers and his father-in-law, and soon became famous for casting church bells. The company went public in ...
fire-control system that calculated the firing data for each gun and with which the gunnery officer fired the guns in unison.[ ''Ikoma'' visited England in July 1910 as part of the ]Japan–British Exhibition
The took place at White City, London in Great Britain from 14 May 1910 to 29 October 1910. It was the largest international exposition that the Empire of Japan had ever participated in and was driven by a desire of Japan to develop a more fav ...
.
The ''Tsukuba''-class ships were reclassified as battlecruiser
The battlecruiser (also written as battle cruiser or battle-cruiser) was a type of capital ship of the first half of the 20th century. These were similar in displacement, armament and cost to battleships, but differed in form and balance of at ...
s in 1912.[ Around 1913–14, the main deck 6-inch guns were removed and six were reinstalled on the upper deck where they replaced four 4.7-inch guns. This gave them a total of ten 6-inch and eight 4.7-inch guns.][ Shortly after the beginning of World War I in August 1914, ''Tsukuba'' was assigned to the 1st South Seas Squadron that searched for the East Asia Squadron in the German-owned islands in the Central Pacific. On 7 October, a landing party from the ship occupied Ponape in the ]Caroline Islands
The Caroline Islands (or the Carolines) are a widely scattered archipelago of tiny islands in the western Pacific Ocean, to the north of New Guinea. Politically, they are divided between the Federated States of Micronesia (FSM) in the centra ...
. ''Ikoma'' joined the squadron in November, shortly before it moved to Fiji in December.[Hirama, p. 142] ''Tsukuba'' was assigned as a gunnery training ship in 1916. By 1917, both ships were assigned to the 2nd Division[Preston, p. 191] and ''Tsukuba'' was sunk by a magazine explosion on 14 January with the loss of 305 crewmen; her wreck was later salvaged and scrapped.[
''Ikoma'' became a gunnery training ship in her turn in 1918][ and her armament was augmented by a pair of 8 cm/40 3rd Year Type anti-aircraft (AA) guns the following year. She was re-rated back to first-class cruiser in 1921 and disarmed in 1922 to fulfill the requirements of the Washington Naval Treaty. The ship was broken up in November 1924.][
]
Notes
Footnotes
References
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{{DEFAULTSORT:Tsukuba Class
Battlecruiser classes
Cruiser classes