Amagi class battlecruiser
Encyclopedia
The was a series
of four battlecruiser
s planned for the Imperial Japanese Navy
as part of the so-called Eight-eight fleet
. The ships were to be named Amagi, , Atago, and Takao; the first three were named for mountains (Mount Amagi
, Mount Akagi
and Mount Atago
), while the fourth was named for the town of Takao
, Formosa
(present-day Kaohsiung, Taiwan). The Amagi design was essentially an enlarged version of the battleship, but with a thinner armored belt
and deck and a modified secondary battery
arrangement.
Limitations imposed by the 1922 Washington Naval Treaty
prevented the class from being completed as designed. However, the treaty had a limited allowance for hulls already under construction to be converted into aircraft carrier
s. Amagi and Akagi were both intended for conversion, but an earthquake
damaged the hull of Amagi so extensively that the ship was scrapped. Akagi was refitted as an aircraft carrier and served with distinction as part of the Kido Butai during the Second World War
, participating in the Japanese attack on Pearl Harbor
before being sunk at the Battle of Midway
.
of 101 ft (30.8 m) and a draft
of 31 ft (9.5 m) and would have used four propeller shafts, powered by Gihon turbines
. The design staff intended to use turbine engines, which were to be powered by 19 Kampon water-tube boiler
s, eleven of which were oil-fired, while the other eight were to have mixed oil and coal for fuel. This system was designed to provide 131200 shp for a top speed of 30 knots. The planned fuel stores amounted to 3,900 tons of oil and 2,500 tons of coal. The ships had a planned cruising speed of 14 knots, and with full fuel stores, the ships would have had a maximum range of 8000 nmi (14,816 km; 9,206.3 mi).
, although an L/50 gun tested in 1920 might have been implemented instead. The guns fired 2,205 lb (1,000 kg) armor-piercing projectiles
with a 494 lb (224 kg) propellant
charge at 2,592 ft/s (790 m/s), at a rate of fire
between 1.5 to 2.5 rounds per minute. Each gun had 90 rounds and an approximate barrel life of 250–300 shots. The turrets would have been arranged along the centerline: two superfiring turrets fore, and three in line aft of the superstructure
. The gun turrets weighed 1,004 tons (1,020 mt), and allowed for depression of −5 degrees and elevation
of 30 degrees.
The secondary battery was to have consisted of sixteen 5.5 in (140 mm) L/50 guns mounted in casemate
s along the center of the ship. These guns fired 83.8 lb (38.0 kg) projectiles and used 22.8–24.2 lb (10.33–10.97 kg) of propellant at a muzzle velocity
of 2,789–2,805 ft/s (850–855 m/s). The guns had a maximum elevation of 25 degrees, which enabled a maximum range of 19140 yards. Four, later increased to six, 4.7 in (120 mm) L/45 anti-aircraft guns were to have been mounted amidships, along with eight 24 in (610 mm) above-water torpedo tubes.
10 in (254 mm) thick, sloped at 12 degrees, and a torpedo bulkhead
2.875 in (73 mm) thick. The main battery barbette
s were designed to have between 9 and 11 in (229–280 mm) of armor plating, and the conning tower
would have had armor ranging in thickness from 3 in (76 mm) to a maximum of 14 in (356 mm). Deck armor was to have been 3.875 in (98 mm) thick.
convinced naval war planners that more fast capital ships were needed, so on 4 April 1907, the Imperial Defence Council approved an "Eight-eight"
policy. This plan originally called for a fleet of eight battleship
s and eight armored cruiser
s that would all be under ten years old (later changed to eight battlecruiser
s and reduced to eight years old). However, the advent of the dreadnought
battleship crippled this plan at the beginning; given Japan's weak and underdeveloped economy and the enormous strain that had been put on it during the Russo-Japanese War (Japan emerged from the war victorious, but bankrupt), the launch of HMS Dreadnought
was a "disaster" for Japan.
In 1907, Japan was halfway to the eight-eight, with two newly delivered battleships (the ) in the fleet and two more (the ) and four armored cruisers authorized or under construction. In addition, three more battleships and four armored cruisers had been authorized, though not funded. However, naval technology was changing; older battleships, including all of Japan's battleships in commission or under construction,While the s were technically "semi-dreadnoughts" due to their heavy secondary battery, they were still made obsolete by Dreadnought. were quickly rendered obsolete with the commissioning of HMS Dreadnought (hence the terms dreadnought and pre-dreadnought
), and armored cruisers were seemingly useless in the face of the new battlecruisers being laid down by Great Britain and Germany. The Imperial Japanese Navy (IJN) recognized this, and proposed in 1909 that two battlecruisers be ordered from British plans, with one to be built in Great Britain and one to be built at home. These two ships became the .
In 1910, there was still authorization for one battleship and four armored cruisers. This battleship, a more heavily armored version of the Kongo-class battlecruisers, became Japan's first super-dreadnought, Fusō
. With these ships, Japan appeared to be getting closer to the eight-eight goal; however, these new ships represented a "new level of naval strength" for the IJN, and they made all previous Japanese capital ships obsolete. This meant that any naval planner aiming for an eight-eight fleet would have to call for seven more battleships and four more battlecruisers at a time when Japan was trying to weather a worldwide economic depression.
After proposals from the IJN in 1911 and 1912 for massive shipbuilding programs, the Cabinet compromised down to a "four-four" plan; under this, three new battleships and no new battlecruisers were authorized. The Navy did not agree, and instead called for an "eight-four" fleet, while the Imperial Defence Council called for the original eight-eight. The Cabinet relented, and by July 1914, it was decided to aim first for an eight-four fleet, followed by the eight-eight fleet. The eight-four plan was presented to the Diet of Japan
in 1915; it aimed to have the eight battleships and four battlecruisers by 1923 with the building of two and two s. The problem with this was that the old plan intended all of the ships of the eight-eight fleet to be under eight years old; by the time these new ships were completed, Fusō and the first two Kongo ships would be past their replacement age.
The plan was approved in 1917, along with funding for two battlecruisers which became the Amagi class. In late 1917, the Navy proposed to expand the eight-four plan by adding two more battlecruisers; this was approved, and two more Amagi-class ships were ordered. However, having eight 16 in (406 mm) gun ships (four battleships and four battlecruisers) on order put an enormous financial strain on Japan, which was spending about a third of its national budget on the Navy. The massive size and scale of its building program was rapidly driving up the cost of naval construction and armament.
was the first ship of the class to be laid down; construction began on 6 December 1920 at the naval yard in Kure
. Amagi followed ten days later at the Yokosuka
naval yard. The projected completion dates for the first pair of ships were December and November 1923, respectively. Atago was laid down in Kobe
at the Kawasaki
shipyard on 22 November 1921, and was projected to be finished in December 1924. Takao, the fourth and final ship of the class, was laid down at the Mitsubishi
shipyard in Nagasaki
on 19 December 1921, and was also projected to be completed in December 1924.
The Washington Naval Treaty
, signed in February 1922, greatly reduced the tonnage allowed for capital ships in the signatory nations. The treaty also instituted a moratorium on new warship construction; battlecruisers canceled under this included one class each from Japan, the United States, and Great Britain: the Amagi class, the and the , respectively. The treaty did allow for battleship and battlecruiser hulls currently under construction to be converted into aircraft carriers, but only if these new carriers were kept under a 27,000-ton limit. Considering that the Amagi class were designed to displace 47000 t (46,257.6 LT; 51,808.6 ST) at full load in their battlecruiser configuration, this would have been a rather difficult displacement to obtain. However, the Americans also had the same problem when designing a conversion of their Lexington class, so an exception, spearheaded by US Assistant Secretary of the Navy
Theodore Roosevelt, Jr.
, was added to the treaty that gave the five signatories the option of converting up to two capital ships that were under construction to 33,000-ton aircraft carriers. This resulted in the United States and Japan quickly reordering two ships each. Japan chose Amagi and Akagi, the two ships nearest to completion, for conversion.
The September 1923 Great Kantō earthquake
in Tokyo caused significant stress damage to the hull of Amagi. The structure was too heavily damaged to be usable, and conversion work was abandoned. Amagi was stricken from the navy list and sold for scrapping, which began on 14 April 1924. The other two ships, Atago and Takao, were officially canceled two years later (31 July 1924) and were broken up
for scrap in their slipway
s. The incomplete Kaga
, on which work had stopped on 5 February 1922, was reordered as a carrier to replace Amagi.
Akagi served as Vice Admiral Chūichi Nagumo
's flagship
in the attack on Pearl Harbor
on 7 December 1941. Nagumo's Kido Butai—composed of the carriers Akagi, Kaga, , , , and , supported by escorts—launched two waves of airstrikes on the American base at Pearl Harbor in a devastating surprise attack. American losses included four battleships and two destroyers sunk and nearly 200 aircraft destroyed.
On 19 February 1942, aircraft from Akagi, Hiryū, Sōryū, and Kaga participated in the bombing of Darwin, Australia. On 27 February, their bombers severely damaged the old American carrier , which was subsequently scuttled by her escort.
Akagi and the carriers Hiryū and Sōryū were sent in March 1942 with a mixed force of battleships, cruisers, and destroyers to the Indian Ocean to engage the British fleet there and to support planned attacks on Ceylon. In the Easter Sunday Raid
on 5 April, aircraft from the carriers struck the British base at Colombo
, destroying a number of aircraft and sinking an armed merchant cruiser and the old destroyer HMS Tenedos
in the harbor. The Japanese fleet also spotted the heavy cruisers and at sea; both ships were sunk in an overwhelming air attack. On 9 April the carriers attacked British installations at Trincomalee
, destroying aircraft and sinking the carrier , the destroyer , and the corvette .
in the Western Pacific. Nagumo, aboard Akagi, led Kaga, Sōryū, and Hiryū and the support ships of the First Carrier Striking Force to Midway. In the initial attack, Japanese planes neutralized a small force of fighter aircraft and inflicted heavy damage to American installations. Torpedo planes and dive-bombers sent from Midway to harry the Japanese fleet had little effect, but the Japanese attack plan had been deciphered by codebreakers, and the American carriers' planes were already en route. Torpedo bombers from , , and joined the attack in succession, forcing the Japanese carriers to maneuver violently to avoid torpedoes and rendering them unable to launch additional aircraft. American dive-bombers, arriving late after difficulty locating the fleet, soon landed fatal strikes on Akagi, Kaga, and Sōryū. Yorktown, handicapped by hits from Hiryūs bombers, managed to return to the fight only to take two torpedo hits a couple of hours later. The burning Yorktown was abandoned, but her scouts pinpointed Hiryūs location, and bombers from Enterprise put Hiryū out of action with four bomb strikes. Japan lost all four carriers of the First Carrier Striking Force at Midway.
Ship class
A ship class is a group of ships of a similar design. This is distinct from a ship-type, which might reflect a similarity of tonnage or intended use. For example, the is a nuclear aircraft carrier of the Nimitz class....
of four battlecruiser
Battlecruiser
Battlecruisers were large capital ships built in the first half of the 20th century. They were developed in the first decade of the century as the successor to the armoured cruiser, but their evolution was more closely linked to that of the dreadnought battleship...
s planned for the Imperial Japanese Navy
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...
as part of the so-called Eight-eight fleet
Eight-eight fleet
The was a Japanese naval strategy formulated for the development of the Imperial Japanese Navy in the first quarter of the 20th century, which laid down that the Japanese navy should include eight first-class battleships and eight armoured cruisers or battlecruisers.-History and development:The...
. The ships were to be named Amagi, , Atago, and Takao; the first three were named for mountains (Mount Amagi
Mount Amagi
is a range of volcanic mountains in central Izu Peninsula in Shizuoka Prefecture, Japan, forming the border between Izu City and Higashi-Izu Town. It is also referred to as the ....
, Mount Akagi
Mount Akagi
is a mountain in Gunma Prefecture, Japan.The broad, low dominantly andesitic stratovolcano rises above the northern end of the Kanto Plain. It contains an elliptical, 3 x 4 km summit caldera with post-caldera lava domes arranged along a NW-SE line. Lake Ono is located at the NE end of the...
and Mount Atago
Mount Atago
is a 924m mountain in the northwestern part of Ukyo-ku, in the city of Kyoto, Kyoto Prefecture, Japan....
), while the fourth was named for the town of Takao
Kaohsiung
Kaohsiung is a city located in southwestern Taiwan, facing the Taiwan Strait on the west. Kaohsiung, officially named Kaohsiung City, is divided into thirty-eight districts. The city is one of five special municipalities of the Republic of China...
, Formosa
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
(present-day Kaohsiung, Taiwan). The Amagi design was essentially an enlarged version of the battleship, but with a thinner armored belt
Belt armor
Belt armor is a layer of heavy metal armor plated on to or within outer hulls of warships, typically on battleships, battlecruisers and cruisers, and on aircraft carriers converted from those types of ships....
and deck and a modified secondary battery
Artillery battery
In military organizations, an artillery battery is a unit of guns, mortars, rockets or missiles so grouped in order to facilitate better battlefield communication and command and control, as well as to provide dispersion for its constituent gunnery crews and their systems...
arrangement.
Limitations imposed by the 1922 Washington Naval Treaty
Washington Naval Treaty
The Washington Naval Treaty, also known as the Five-Power Treaty, was an attempt to cap and limit, and "prevent 'further' costly escalation" of the naval arms race that had begun after World War I between various International powers, each of which had significant naval fleets. The treaty was...
prevented the class from being completed as designed. However, the treaty had a limited allowance for hulls already under construction to be converted into aircraft carrier
Aircraft carrier
An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...
s. Amagi and Akagi were both intended for conversion, but an earthquake
1923 Great Kanto earthquake
The struck the Kantō plain on the Japanese main island of Honshū at 11:58:44 am JST on September 1, 1923. Varied accounts hold that the duration of the earthquake was between 4 and 10 minutes...
damaged the hull of Amagi so extensively that the ship was scrapped. Akagi was refitted as an aircraft carrier and served with distinction as part of the Kido Butai during the Second World War
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, participating in the Japanese attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
before being sunk at the Battle of Midway
Battle of Midway
The Battle of Midway is widely regarded as the most important naval battle of the Pacific Campaign of World War II. Between 4 and 7 June 1942, approximately one month after the Battle of the Coral Sea and six months after Japan's attack on Pearl Harbor, the United States Navy decisively defeated...
.
Dimensions and machinery
The ships had a planned displacement of 41217 t (40,565.9 LT; 45,434 ST) and 47000 t (46,257.6 LT; 51,808.6 ST) at a full load. The class design was 820 ft 3 in (250 m) long at the waterline, and 826 ft 1 in (251.8 m) overall. The ships would have had a beamBeam (nautical)
The beam of a ship is its width at the widest point. Generally speaking, the wider the beam of a ship , the more initial stability it has, at expense of reserve stability in the event of a capsize, where more energy is required to right the vessel from its inverted position...
of 101 ft (30.8 m) and a draft
Draft (hull)
The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...
of 31 ft (9.5 m) and would have used four propeller shafts, powered by Gihon turbines
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....
. The design staff intended to use turbine engines, which were to be powered by 19 Kampon water-tube boiler
Water-tube boiler
A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes...
s, eleven of which were oil-fired, while the other eight were to have mixed oil and coal for fuel. This system was designed to provide 131200 shp for a top speed of 30 knots. The planned fuel stores amounted to 3,900 tons of oil and 2,500 tons of coal. The ships had a planned cruising speed of 14 knots, and with full fuel stores, the ships would have had a maximum range of 8000 nmi (14,816 km; 9,206.3 mi).
Armament
The ships were to be equipped with a main battery of ten 16 in (406 mm) L/45L/45 denotes the length of the gun barrels; in this case, the gun is 45 calibers, meaning that the gun is 45 times long as it is in diameter. guns in five twin turretsGun turret
A gun turret is a weapon mount that protects the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in many directions.The turret is also a rotating weapon platform...
, although an L/50 gun tested in 1920 might have been implemented instead. The guns fired 2,205 lb (1,000 kg) armor-piercing projectiles
Armor-piercing shot and shell
An armor-piercing shell is a type of ammunition designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions...
with a 494 lb (224 kg) propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
charge at 2,592 ft/s (790 m/s), at a rate of fire
Rate of fire
Rate of fire is the frequency at which a specific weapon can fire or launch its projectiles. It is usually measured in rounds per minute , or per second .-Overview:...
between 1.5 to 2.5 rounds per minute. Each gun had 90 rounds and an approximate barrel life of 250–300 shots. The turrets would have been arranged along the centerline: two superfiring turrets fore, and three in line aft of the superstructure
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...
. The gun turrets weighed 1,004 tons (1,020 mt), and allowed for depression of −5 degrees and elevation
Elevation (ballistics)
In ballistics, the elevation is the angle between the horizontal plane and the direction of the barrel of a gun, mortar or heavy artillery. Originally, elevation was a linear measure of how high the gunners had to physically lift the muzzle of a gun up from the gun carriage to hit targets at a...
of 30 degrees.
The secondary battery was to have consisted of sixteen 5.5 in (140 mm) L/50 guns mounted in casemate
Casemate
A casemate, sometimes rendered casement, is a fortified gun emplacement or armored structure from which guns are fired. originally a vaulted chamber in a fortress.-Origin of the term:...
s along the center of the ship. These guns fired 83.8 lb (38.0 kg) projectiles and used 22.8–24.2 lb (10.33–10.97 kg) of propellant at a muzzle velocity
Muzzle velocity
Muzzle velocity is the speed a projectile has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets , to more than in modern rifles with high-performance cartridges such as the .220 Swift and .204 Ruger, all the way to for tank guns...
of 2,789–2,805 ft/s (850–855 m/s). The guns had a maximum elevation of 25 degrees, which enabled a maximum range of 19140 yards. Four, later increased to six, 4.7 in (120 mm) L/45 anti-aircraft guns were to have been mounted amidships, along with eight 24 in (610 mm) above-water torpedo tubes.
Armor
It was planned that the Amagi class would be protected by a main beltBelt armor
Belt armor is a layer of heavy metal armor plated on to or within outer hulls of warships, typically on battleships, battlecruisers and cruisers, and on aircraft carriers converted from those types of ships....
10 in (254 mm) thick, sloped at 12 degrees, and a torpedo bulkhead
Torpedo bulkhead
A torpedo bulkhead is a type of armor common on the more heavily armored warships, especially battleships and battlecruisers of the early 20th century. It is designed to keep the ship afloat even if the hull was struck underneath the belt armor by a shell or by a torpedo...
2.875 in (73 mm) thick. The main battery barbette
Barbette
A barbette is a protective circular armour feature around a cannon or heavy artillery gun. The name comes from the French phrase en barbette referring to the practice of firing a field gun over a parapet rather than through an opening . The former gives better angles of fire but less protection...
s were designed to have between 9 and 11 in (229–280 mm) of armor plating, and the conning tower
Conning tower
A conning tower is a raised platform on a ship or submarine, often armored, from which an officer can con the vessel; i.e., give directions to the helmsman. It is usually located as high on the ship as practical, to give the conning team good visibility....
would have had armor ranging in thickness from 3 in (76 mm) to a maximum of 14 in (356 mm). Deck armor was to have been 3.875 in (98 mm) thick.
Background
Experiences in the Russo-Japanese WarRusso-Japanese War
The Russo-Japanese War was "the first great war of the 20th century." It grew out of rival imperial ambitions of the Russian Empire and Japanese Empire over Manchuria and Korea...
convinced naval war planners that more fast capital ships were needed, so on 4 April 1907, the Imperial Defence Council approved an "Eight-eight"
Eight-eight fleet
The was a Japanese naval strategy formulated for the development of the Imperial Japanese Navy in the first quarter of the 20th century, which laid down that the Japanese navy should include eight first-class battleships and eight armoured cruisers or battlecruisers.-History and development:The...
policy. This plan originally called for a fleet of eight battleship
Battleship
A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...
s and eight armored cruiser
Armored cruiser
The armored cruiser was a type of warship of the late 19th and early 20th centuries. Like other types of cruiser, the armored cruiser was a long-range, independent warship, capable of defeating any ship apart from a battleship, and fast enough to outrun any battleships it encountered.The first...
s that would all be under ten years old (later changed to eight battlecruiser
Battlecruiser
Battlecruisers were large capital ships built in the first half of the 20th century. They were developed in the first decade of the century as the successor to the armoured cruiser, but their evolution was more closely linked to that of the dreadnought battleship...
s and reduced to eight years old). However, the advent of the dreadnought
Dreadnought
The dreadnought was the predominant type of 20th-century battleship. The first of the kind, the Royal Navy's had such an impact when launched in 1906 that similar battleships built after her were referred to as "dreadnoughts", and earlier battleships became known as pre-dreadnoughts...
battleship crippled this plan at the beginning; given Japan's weak and underdeveloped economy and the enormous strain that had been put on it during the Russo-Japanese War (Japan emerged from the war victorious, but bankrupt), the launch of HMS Dreadnought
HMS Dreadnought (1906)
HMS Dreadnought was a battleship of the British Royal Navy that revolutionised naval power. Her entry into service in 1906 represented such a marked advance in naval technology that her name came to be associated with an entire generation of battleships, the "dreadnoughts", as well as the class of...
was a "disaster" for Japan.
In 1907, Japan was halfway to the eight-eight, with two newly delivered battleships (the ) in the fleet and two more (the ) and four armored cruisers authorized or under construction. In addition, three more battleships and four armored cruisers had been authorized, though not funded. However, naval technology was changing; older battleships, including all of Japan's battleships in commission or under construction,While the s were technically "semi-dreadnoughts" due to their heavy secondary battery, they were still made obsolete by Dreadnought. were quickly rendered obsolete with the commissioning of HMS Dreadnought (hence the terms dreadnought and pre-dreadnought
Pre-dreadnought
Pre-dreadnought battleship is the general term for all of the types of sea-going battleships built between the mid-1890s and 1905. Pre-dreadnoughts replaced the ironclad warships of the 1870s and 1880s...
), and armored cruisers were seemingly useless in the face of the new battlecruisers being laid down by Great Britain and Germany. The Imperial Japanese Navy (IJN) recognized this, and proposed in 1909 that two battlecruisers be ordered from British plans, with one to be built in Great Britain and one to be built at home. These two ships became the .
In 1910, there was still authorization for one battleship and four armored cruisers. This battleship, a more heavily armored version of the Kongo-class battlecruisers, became Japan's first super-dreadnought, Fusō
Japanese battleship Fuso
The Japanese battleship Fusō , was a part of the Imperial Japanese Navy, the lead ship of the Fusō-class. She was laid down by the Kure Kaigun Koshō on 11 March 1912, launched on 28 March 1914 and completed on 18 November 1915...
. With these ships, Japan appeared to be getting closer to the eight-eight goal; however, these new ships represented a "new level of naval strength" for the IJN, and they made all previous Japanese capital ships obsolete. This meant that any naval planner aiming for an eight-eight fleet would have to call for seven more battleships and four more battlecruisers at a time when Japan was trying to weather a worldwide economic depression.
After proposals from the IJN in 1911 and 1912 for massive shipbuilding programs, the Cabinet compromised down to a "four-four" plan; under this, three new battleships and no new battlecruisers were authorized. The Navy did not agree, and instead called for an "eight-four" fleet, while the Imperial Defence Council called for the original eight-eight. The Cabinet relented, and by July 1914, it was decided to aim first for an eight-four fleet, followed by the eight-eight fleet. The eight-four plan was presented to the Diet of Japan
Diet of Japan
The is Japan's bicameral legislature. It is composed of a lower house, called the House of Representatives, and an upper house, called the House of Councillors. Both houses of the Diet are directly elected under a parallel voting system. In addition to passing laws, the Diet is formally...
in 1915; it aimed to have the eight battleships and four battlecruisers by 1923 with the building of two and two s. The problem with this was that the old plan intended all of the ships of the eight-eight fleet to be under eight years old; by the time these new ships were completed, Fusō and the first two Kongo ships would be past their replacement age.
The plan was approved in 1917, along with funding for two battlecruisers which became the Amagi class. In late 1917, the Navy proposed to expand the eight-four plan by adding two more battlecruisers; this was approved, and two more Amagi-class ships were ordered. However, having eight 16 in (406 mm) gun ships (four battleships and four battlecruisers) on order put an enormous financial strain on Japan, which was spending about a third of its national budget on the Navy. The massive size and scale of its building program was rapidly driving up the cost of naval construction and armament.
Construction, cancellation, and conversion
Kure, Hiroshima
is a city in Hiroshima prefecture, Japan.As of October 1, 2010, the city has an estimated population of 240,820 and a population density of 681 persons per km². The total area is 353.74 km².- History :...
. Amagi followed ten days later at the Yokosuka
Yokosuka, Kanagawa
is a city located in Kanagawa, Japan. As of 2010, the city had an estimated population of 419,067 and a population density of 4,160 people per km². It covered an area of 100.62 km²...
naval yard. The projected completion dates for the first pair of ships were December and November 1923, respectively. Atago was laid down in Kobe
Kobe
, pronounced , is the fifth-largest city in Japan and is the capital city of Hyōgo Prefecture on the southern side of the main island of Honshū, approximately west of Osaka...
at the Kawasaki
Kawasaki Heavy Industries
is an international corporation based in Japan. It has headquarters in both Chūō-ku, Kobe and Minato, Tokyo.The company is named after its founder Shōzō Kawasaki and has no connection with the city of Kawasaki, Kanagawa....
shipyard on 22 November 1921, and was projected to be finished in December 1924. Takao, the fourth and final ship of the class, was laid down at the Mitsubishi
Mitsubishi
The Mitsubishi Group , Mitsubishi Group of Companies, or Mitsubishi Companies is a Japanese multinational conglomerate company that consists of a range of autonomous businesses which share the Mitsubishi brand, trademark and legacy...
shipyard in Nagasaki
Nagasaki
is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan. Nagasaki was founded by the Portuguese in the second half of the 16th century on the site of a small fishing village, formerly part of Nishisonogi District...
on 19 December 1921, and was also projected to be completed in December 1924.
The Washington Naval Treaty
Washington Naval Treaty
The Washington Naval Treaty, also known as the Five-Power Treaty, was an attempt to cap and limit, and "prevent 'further' costly escalation" of the naval arms race that had begun after World War I between various International powers, each of which had significant naval fleets. The treaty was...
, signed in February 1922, greatly reduced the tonnage allowed for capital ships in the signatory nations. The treaty also instituted a moratorium on new warship construction; battlecruisers canceled under this included one class each from Japan, the United States, and Great Britain: the Amagi class, the and the , respectively. The treaty did allow for battleship and battlecruiser hulls currently under construction to be converted into aircraft carriers, but only if these new carriers were kept under a 27,000-ton limit. Considering that the Amagi class were designed to displace 47000 t (46,257.6 LT; 51,808.6 ST) at full load in their battlecruiser configuration, this would have been a rather difficult displacement to obtain. However, the Americans also had the same problem when designing a conversion of their Lexington class, so an exception, spearheaded by US Assistant Secretary of the Navy
Assistant Secretary of the Navy
Assistant Secretary of the Navy is the title given to certain civilian senior officials in the United States Department of the Navy....
Theodore Roosevelt, Jr.
Theodore Roosevelt, Jr.
Theodore D. Roosevelt, Jr. , was an American political and business leader, a Medal of Honor recipient who fought in both of the 20th century's world wars. He was the eldest son of President Theodore Roosevelt from his second wife Edith Roosevelt...
, was added to the treaty that gave the five signatories the option of converting up to two capital ships that were under construction to 33,000-ton aircraft carriers. This resulted in the United States and Japan quickly reordering two ships each. Japan chose Amagi and Akagi, the two ships nearest to completion, for conversion.
The September 1923 Great Kantō earthquake
1923 Great Kanto earthquake
The struck the Kantō plain on the Japanese main island of Honshū at 11:58:44 am JST on September 1, 1923. Varied accounts hold that the duration of the earthquake was between 4 and 10 minutes...
in Tokyo caused significant stress damage to the hull of Amagi. The structure was too heavily damaged to be usable, and conversion work was abandoned. Amagi was stricken from the navy list and sold for scrapping, which began on 14 April 1924. The other two ships, Atago and Takao, were officially canceled two years later (31 July 1924) and were broken up
Ship breaking
Ship breaking or ship demolition is a type of ship disposal involving the breaking up of ships for scrap recycling. Most ships have a lifespan of a few decades before there is so much wear that refitting and repair becomes uneconomical. Ship breaking allows materials from the ship, especially...
for scrap in their slipway
Slipway
A slipway, boat slip or just a slip, 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. They are also used for launching and retrieving small boats on trailers and flying boats on their undercarriage. The...
s. The incomplete Kaga
Japanese aircraft carrier Kaga
Kaga was an aircraft carrier of the Imperial Japanese Navy , named after the former Kaga Province in present-day Ishikawa Prefecture...
, on which work had stopped on 5 February 1922, was reordered as a carrier to replace Amagi.
Akagis career as an aircraft carrier
The conversion of Akagi began on 19 November 1923, and was completed in March 1927. However, the strange assortment of flight decks fitted on Akagi—a main landing deck superimposed over two short take-off decks—proved unsatisfactory, and the ship was withdrawn from active service in 1935 for modernization. The lower two flight decks were removed, the main deck was lengthened to 817 ft (249 m), and a third elevator was added. Refitting was completed in 1938. Akagi supported operations off China in early 1939 and 1940, and underwent an overhaul in November 1940.Akagi served as Vice Admiral Chūichi Nagumo
Chuichi Nagumo
was a Japanese admiral in the Imperial Japanese Navy during World War II and one time commander of the Kido Butai . He committed suicide during the Battle of Saipan.-Early life:...
's flagship
Flagship
A flagship is a vessel used by the commanding officer of a group of naval ships, reflecting the custom of its commander, characteristically a flag officer, flying a distinguishing flag...
in the attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
on 7 December 1941. Nagumo's Kido Butai—composed of the carriers Akagi, Kaga, , , , and , supported by escorts—launched two waves of airstrikes on the American base at Pearl Harbor in a devastating surprise attack. American losses included four battleships and two destroyers sunk and nearly 200 aircraft destroyed.
On 19 February 1942, aircraft from Akagi, Hiryū, Sōryū, and Kaga participated in the bombing of Darwin, Australia. On 27 February, their bombers severely damaged the old American carrier , which was subsequently scuttled by her escort.
Akagi and the carriers Hiryū and Sōryū were sent in March 1942 with a mixed force of battleships, cruisers, and destroyers to the Indian Ocean to engage the British fleet there and to support planned attacks on Ceylon. In the Easter Sunday Raid
Easter Sunday Raid
The Easter Sunday Raid was an air attack by carrier-based aircraft of the Imperial Japanese Navy against Colombo, Ceylon , on Easter Sunday, 5 April 1942, during World War II. This attack was part of the Indian Ocean Raid, and was followed a few days later by a similar attack on Trincomalee...
on 5 April, aircraft from the carriers struck the British base at Colombo
Colombo
Colombo is the largest city of Sri Lanka. It is located on the west coast of the island and adjacent to Sri Jayawardenapura Kotte, the capital of Sri Lanka. Colombo is often referred to as the capital of the country, since Sri Jayawardenapura Kotte is a satellite city of Colombo...
, destroying a number of aircraft and sinking an armed merchant cruiser and the old destroyer HMS Tenedos
HMS Tenedos (H04)
HMS Tenedos was an Admiralty 'S' class destroyer. Commissioned in 1919 she served throughout the period between the two World Wars.Laid down on the 6 December 1917, she was constructed by Hawthorn Leslie of Tyne, and was completed in 1918....
in the harbor. The Japanese fleet also spotted the heavy cruisers and at sea; both ships were sunk in an overwhelming air attack. On 9 April the carriers attacked British installations at Trincomalee
Trincomalee
Trincomalee is a port city in Eastern Province, Sri Lanka and lies on the east coast of the island, about 113 miles south of Jaffna. It has a population of approximately 100,000 . The city is built on a peninsula, which divides the inner and outer harbours. Overlooking the Kottiyar Bay,...
, destroying aircraft and sinking the carrier , the destroyer , and the corvette .
Battle of Midway
In late May 1942, in an effort to draw out and destroy the elusive American carriers, Japanese forces organized attacks on the Aleutian Islands in Alaska and Midway AtollBattle of Midway
The Battle of Midway is widely regarded as the most important naval battle of the Pacific Campaign of World War II. Between 4 and 7 June 1942, approximately one month after the Battle of the Coral Sea and six months after Japan's attack on Pearl Harbor, the United States Navy decisively defeated...
in the Western Pacific. Nagumo, aboard Akagi, led Kaga, Sōryū, and Hiryū and the support ships of the First Carrier Striking Force to Midway. In the initial attack, Japanese planes neutralized a small force of fighter aircraft and inflicted heavy damage to American installations. Torpedo planes and dive-bombers sent from Midway to harry the Japanese fleet had little effect, but the Japanese attack plan had been deciphered by codebreakers, and the American carriers' planes were already en route. Torpedo bombers from , , and joined the attack in succession, forcing the Japanese carriers to maneuver violently to avoid torpedoes and rendering them unable to launch additional aircraft. American dive-bombers, arriving late after difficulty locating the fleet, soon landed fatal strikes on Akagi, Kaga, and Sōryū. Yorktown, handicapped by hits from Hiryūs bombers, managed to return to the fight only to take two torpedo hits a couple of hours later. The burning Yorktown was abandoned, but her scouts pinpointed Hiryūs location, and bombers from Enterprise put Hiryū out of action with four bomb strikes. Japan lost all four carriers of the First Carrier Striking Force at Midway.