Japanese Aircraft Carrier Ryūhō
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was a
light aircraft carrier A light aircraft carrier, or light fleet carrier, is an aircraft carrier smaller than the Fleet carrier, standard carriers of a navy. The precise definition of the type varies by country; light carriers typically have a complement of aircraft onl ...
of 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, Potsdam Declaration, when it was dissolved followin ...
. She was converted from the
submarine tender A submarine tender, in British English a submarine depot ship, is a type of depot ship that supplies and supports submarines. Development Submarines are small compared to most oceangoing vessels, and generally cannot carry large amounts of foo ...
, which had been used in the
Second Sino-Japanese War The Second Sino-Japanese War was fought between the Republic of China (1912–1949), Republic of China and the Empire of Japan between 1937 and 1945, following a period of war localized to Manchuria that started in 1931. It is considered part ...
. One of the least successful of the light aircraft carrier conversions due to her small size, slow speed and weak construction, during
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, ''Ryūhō'' was used primarily as an aircraft transport and for training purposes, although she was also involved in a number of combat missions, including the
Battle of the Philippine Sea The Battle of the Philippine Sea was a major naval battle of World War II on 19–20 June 1944 that eliminated the Imperial Japanese Navy's ability to conduct large-scale carrier actions. It took place during the United States' amphibious r ...
.


Background

The
London Naval Treaty The London Naval Treaty, officially the Treaty for the Limitation and Reduction of Naval Armament, was an agreement between the United Kingdom, Empire of Japan, Japan, French Third Republic, France, Kingdom of Italy, Italy, and the United Stat ...
imposed limitations on new construction of major capital warships for the major world powers. The Imperial Japanese Navy responded in part by the construction of auxiliary vessels, such as
fleet oiler A replenishment oiler or replenishment tanker is a naval auxiliary ship with fuel tanks and dry cargo holds which can supply both fuel and dry stores during underway replenishment (UNREP) at sea. Many countries have used replenishment oilers. T ...
s and submarine tenders, designed so that they could be converted quickly into aircraft carriers in time of conflict. ''Taigei'' was ordered as part of the
1st Naval Armaments Supplement Programme The , otherwise known as the "Circle One" plan was the first of four expansion plans of the Imperial Japanese Navy between 1930 and the start of World War II. Background The London Naval Treaty placed severe restrictions on Japan's naval capabil ...
of 1932.


Design

Although ''Taigei'' was designed from the onset for possible later conversion to an aircraft carrier, the design proved to have many shortcomings. The basic design of the hull suffered from a high
freeboard In sailing and boating, a vessel's freeboard is the distance from the waterline to the upper deck level, measured at the lowest point of sheer where water can enter the boat or ship. In commercial vessels, the latter criterion measured relativ ...
with a shallow draught, which resulted in poor stability. Although extensive use of electric
arc welding Arc welding is a welding process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals, when cool, result in a joining of the metals. It is a type of welding that uses a welding power ...
on the hull speeded construction time and was considered highly innovative for the time, lack of experience with this technique led to many weak welds, and the ship suffered from frequent cracks. Inadequate sectioning into waterproof compartments below her waterline, combined with the weak construction of her hull, also made the ship vulnerable in combat situations.Sturton, p. 181 The new vessel was also plagued by the poor performance of its
diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...
s, which gave only half the output expected. Conversion of ''Taigei'' into an aircraft carrier entailed adding a flight deck. Two elevators connected the flight deck to the hangar deck below. During the conversion, the problematic diesel engines were replaced by
Kampon The was the externally operating division of the Ministry of the Navy of Japan responsible for the administration of naval vessel construction. From 1923 onward, it took on the role of a research institution for the research and development of n ...
steam turbine A steam turbine or steam turbine engine is a machine or heat engine that extracts thermal energy from pressurized steam and uses it to do mechanical work utilising a rotating output shaft. Its modern manifestation was invented by Sir Charles Par ...
s of the same design as was used in the . While greatly improving on engine performance and reliability, the more powerful engines were not powerful enough to overcome the increased displacement and side bulges in the hull of the modified design, and speed was decreased by two knots. Her flight wing theoretically consisted of 31 aircraft, typically a mixture of
Mitsubishi A6M The Mitsubishi A6M "Zero" is a long-range carrier-capable fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries. It was operated by the Imperial Japanese Navy (IJN) from 1940 to 1945. The ...
"Zero" fighters,
Aichi D3A The Aichi D3A (Navy designation "Type 99 Carrier Bomber"; World War II Allied names for Japanese aircraft, Allied reporting name "Val") is a World War II carrier-borne dive bomber. It was the primary dive bomber of the Imperial Japanese Na ...
"Val" and
Yokosuka D4Y The is a two-seat carrier-based dive bomber developed by the Yokosuka Naval Air Technical Arsenal and operated by the Imperial Japanese Navy from 1942 to 1945 during World War II. Development of the aircraft began in 1938. The first D4Y1 was co ...
"Judy"
dive bomber A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy for the bomb it drops. Diving towards the target simplifies the bomb's trajectory and allows the pilot to keep visual contact througho ...
s, and
Nakajima B5N The Nakajima B5N (, World War II Allied names for Japanese aircraft, Allied reporting name "Kate") was the standard Carrier-based aircraft, carrier-based torpedo bomber of the Imperial Japanese Navy (IJN) for much of World War II. It also served ...
"Kate"
torpedo bomber A torpedo bomber is a military aircraft designed primarily to attack ships with aerial torpedoes. Torpedo bombers came into existence just before the World War I, First World War almost as soon as aircraft were built that were capable of carryin ...
s, but her small size limited her usefulness in combat operations. In August 1944, her flight deck was lengthened to 198.1 meters, but the number of aircraft embarked could only be increased to 36.


Operational history


As the submarine tender ''Taigei''

''Taigei'' was
laid down Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship. Keel laying is one ...
at
Yokosuka Naval Arsenal was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy, and was located at Yokosuka, Kanagawa, Yokosuka, Kanagawa Prefecture on Tokyo Bay, south of Yokohama. History In 1866, the Tokugawa shogunate govern ...
on 12 April 1933, and was launched on 16 November 1933. Construction was rushed by plans to have
Emperor Hirohito , Posthumous name, posthumously honored as , was the 124th emperor of Japan according to the traditional order of succession, from 25 December 1926 until Death and state funeral of Hirohito, his death in 1989. He remains Japan's longest-reigni ...
attend the launching ceremony and due to inexperience with the electric arc welding method, portions of the hull warped during construction. Immediately after the launching ceremony, ''Taigei'' was returned to the
dry dock A dry dock (sometimes drydock or dry-dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, ...
for repairs and modifications, which involved replacement of damaged sections by the traditional rivet construction method. Formally commissioned on 31 March 1934, ''Taigei'' was soon damaged by a
typhoon A typhoon is a tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere and which produces sustained hurricane-force winds of at least . This region is referred to as the Northwestern Pacific Basin, accounting for a ...
in what was later called the " Fourth Fleet Incident". Seawater ingression from faulty waterproof doors shorted the electric system, disabling her steering and the waves from the typhoon cracked a number of the welds in her hull. Further repairs at Yokosuka Naval Arsenal were scheduled for early 1936, but were delayed by the February 26 Incident. It was not until September 1938 that ''Taigei'' was deemed fully operational, and assigned to its design role as
flagship A flagship is a vessel used by the commanding officer of a group of navy, naval ships, characteristically a flag officer entitled by custom to fly a distinguishing flag. Used more loosely, it is the lead ship in a fleet of vessels, typically ...
of a submarine squadron. From 1938 to 1940, ''Taigei'' performed normal operations in both northern and southern waters off Japan, with her primary mission being to support submarine operations off the coast of China from her home port of
Kure is a city in the Hiroshima Prefecture, Japan. , the city had an estimated population of 208,024 in 106,616 households and a population density of 590 persons per km2. The total area of the city is . With a strong industrial and naval heritage, ...
in the
Second Sino-Japanese War The Second Sino-Japanese War was fought between the Republic of China (1912–1949), Republic of China and the Empire of Japan between 1937 and 1945, following a period of war localized to Manchuria that started in 1931. It is considered part ...
. She was reassigned from the 1st Fleet to the 6th Fleet on 15 November 1940 and was based at
Kwajalein Atoll Kwajalein Atoll (; Marshallese language, Marshallese: ) is part of the Marshall Islands, Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking re ...
from 10 April 1941. Shortly before the start of hostilities in the
Pacific War The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theatre, was the Theater (warfare), theatre of World War II fought between the Empire of Japan and the Allies of World War II, Allies in East Asia, East and Southeast As ...
, ''Taigei'' was ordered back to Japan for conversion into a light
aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and hangar facilities for supporting, arming, deploying and recovering carrier-based aircraft, shipborne aircraft. Typically it is the ...
, arriving at Kure on 4 December. The conversion work began on 20 December at Yokosuka Naval Arsenal, and was originally scheduled to be completed within three months; however, numerous problems and issues arose, and the conversion work was not completed until 30 November 1942. She gained the distinction of being the only major warship damaged in the Doolittle Raid on 18 April. She received one direct hit from a bomb on the bow, plus several small
incendiary bomb Incendiary weapons, incendiary devices, incendiary munitions, or incendiary bombs are weapons designed to start fires. They may destroy structures or sensitive equipment using fire, and sometimes operate as anti-personnel weaponry. Incendiarie ...
hits, with seven casualties among her crew. As an aircraft carrier, the vessel was renamed ''Ryūhō''.


As the aircraft carrier ''Ryūhō''

On 30 November 1942, with conversion and repairs complete, ''Ryūhō'' was officially assigned to the 3rd Fleet. On her first mission on 11 December, under the command of Captain Yoshio Kamei, she was sent to the Japanese naval base at Truk escorted by the destroyer . Her normal aircraft complement consisted of 15
Mitsubishi A6M The Mitsubishi A6M "Zero" is a long-range carrier-capable fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries. It was operated by the Imperial Japanese Navy (IJN) from 1940 to 1945. The ...
"Zero" fighters and 16
Aichi D3A The Aichi D3A (Navy designation "Type 99 Carrier Bomber"; World War II Allied names for Japanese aircraft, Allied reporting name "Val") is a World War II carrier-borne dive bomber. It was the primary dive bomber of the Imperial Japanese Na ...
"Val" dive bombers, but for this mission, she was carrying 20 light bombers with their pilots and crews on a ferry mission. At 09:10 on 12 December, she was hit by a single torpedo on the starboard side from the American submarine near Hachijojima, and was immediately forced to return to Yokosuka for emergency repairs, and remained out of operation until early 1943. On 19 March ''Ryūhō'' began a series of uneventful aircraft ferry missions to occupied islands in the South Pacific. On 11 June, ''Ryūhō'' embarked the marooned survivors of the air group of , which had been damaged by an American submarine. She was subsequently assigned to the
Second Carrier Division was an aircraft carrier unit of the Imperial Japanese Navy's First Air Fleet. At the beginning of the Pacific War, Pacific Campaign of World War II, the Second Carrier Division consisted of the fleet carriers ''Japanese aircraft carrier Sōryū, ...
of the 3rd Fleet, accompanying the
escort carrier The escort carrier or escort aircraft carrier (U.S. hull classification symbol CVE), also called a "jeep carrier" or "baby flattop" in the United States Navy (USN) or "Woolworth Carrier" by the Royal Navy, was a small and slower type of aircraf ...
s and to Truk and back, and remaining based in the
Seto Inland Sea The , sometimes shortened to the Inland Sea, is the body of water separating Honshu, Shikoku, and Kyushu, three of the four main islands of Japan. It serves as a waterway connecting the Pacific Ocean to the Sea of Japan. It connects to Osaka Ba ...
for training missions. In October, ''Ryūhō'' was sent on another aircraft ferry mission to
Singapore Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...
, returning to Kure on 5 November. On 25 November, she departed with ''Hiyō'' and escorts on a long circular patrol and training mission, sailing to
Manila Manila, officially the City of Manila, is the Capital of the Philippines, capital and second-most populous city of the Philippines after Quezon City, with a population of 1,846,513 people in 2020. Located on the eastern shore of Manila Bay on ...
, then to Singapore, then to
Tarakan Tarakan is an island and co-extensively the sole city within the Indonesian province of North Kalimantan. The island city is the largest urban area in North Kalimantan population-wise and is located in northern Borneo, midway along the coast of ...
, then
Palau Palau, officially the Republic of Palau, is an island country in the Micronesia subregion of Oceania in the western Pacific Ocean. The Republic of Palau consists of approximately 340 islands and is the western part of the Caroline Islands ...
, then Truk, then
Saipan Saipan () is the largest island and capital of the Northern Mariana Islands, an unincorporated Territories of the United States, territory of the United States in the western Pacific Ocean. According to 2020 estimates by the United States Cens ...
, and finally returning to Kure on 2 January 1944. After two more uneventful patrol and training missions between Japan and the
Marianas Islands The Mariana Islands ( ; ), also simply the Marianas, are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, between the 12th and 21st pa ...
, ''Ryūhō'' was sent to the Japanese anchorage at Tawi Tawi in May 1944 to join the
Combined Fleet The was the main sea-going component of the Imperial Japanese Navy. Until 1933, the Combined Fleet was not a permanent organization, but a temporary force formed for the duration of a conflict or major naval maneuvers from various units norm ...
. From there, she sailed with the Combined Fleet to participate in the
Battle of the Philippine Sea The Battle of the Philippine Sea was a major naval battle of World War II on 19–20 June 1944 that eliminated the Imperial Japanese Navy's ability to conduct large-scale carrier actions. It took place during the United States' amphibious r ...
as part of "Force B" (with the carriers ''Hiyō'', , the battleship , the cruiser , and eight destroyers). On 19 June, she launched an air strike against
Task Force 58 The Fast Carrier Task Force (TF 38 when assigned to Third Fleet, TF 58 when assigned to Fifth Fleet) was a group of ships in World War II. It was the main striking force of the United States Navy in the Pacific War from January 1944 through th ...
, but scored no hits; nearly all of ''Ryūhōs aircraft were shot down by the swarms of American
F6F Hellcat The Grumman F6F Hellcat is an American carrier-based fighter aircraft of World War II. Designed to replace the earlier F4F Wildcat and to counter the Japanese Mitsubishi A6M Zero, it was the United States Navy's dominant fighter in the second ...
fighters and the anti-aircraft guns of the American fleet. On 20 June, ''Ryūhō'' was attacked by four
Grumman TBF Avenger The Grumman TBF Avenger (designated TBM for aircraft manufactured by General Motors) is an American World War II-era torpedo bomber developed initially for the United States Navy and Marine Corps, and eventually used by several air and naval a ...
torpedo bomber A torpedo bomber is a military aircraft designed primarily to attack ships with aerial torpedoes. Torpedo bombers came into existence just before the World War I, First World War almost as soon as aircraft were built that were capable of carryin ...
s from the aircraft carrier . She suffered only slight damage from near misses. ''Ryūhō'' engaged in several more patrol and training missions near Japan. On 25 October, with the escort carrier , ''Ryūhō'' set sail from
Sasebo Naval District was the third of five main administrative districts of the pre-war Imperial Japanese Navy. Its territory included the western and southern coastline of Kyūshū, the Ryukyu Islands, Taiwan and Korea, as well as patrols in the East China Sea and t ...
on another aircraft ferry mission to
Keelung Keelung ( ; zh, p=Jīlóng, c=基隆, poj=Ke-lâng), Chilung or Jilong ( ; ), officially known as Keelung City, is a major port city in northeastern Taiwan. The city is part of the Taipei–Keelung metropolitan area with neighboring New Ta ...
,
Formosa Taiwan, officially the Republic of China (ROC), is a country in East Asia. The island of Taiwan, formerly known to Westerners as Formosa, has an area of and makes up 99% of the land under ROC control. It lies about across the Taiwan Strait f ...
. They were escorted by the destroyers , and . They returned to Kure on 2 November. From 7 to 15 November, ''Ryūhō'' briefly flew the flag of the Commander of the
Mobile Fleet Mobile may refer to: Places * Mobile, Alabama, a U.S. port city * Mobile County, Alabama * Mobile, Arizona, a small town near Phoenix, U.S. * Mobile, Newfoundland and Labrador Arts, entertainment, and media Music Groups and labels * Mobile (b ...
, Admiral
Jisaburō Ozawa was an admiral in the Imperial Japanese Navy during World War II. Ozawa held several important commands at sea throughout the duration of the conflict ( Southern Expeditionary Fleet, 3rd Fleet, 1st Mobile Fleet, and the Combined Fleet). Ozawa ...
.


Final mission

On 31 December 1944, ''Ryūhō'' sailed for Formosa with a load of 58 ''
Ohka The Yokosuka MXY-7 is a purpose-built, rocket-powered human-guided ''kamikaze'' attack-aircraft deployed by Japan against Allied ships in the Pacific Ocean theater toward the end of World War II. Although extremely fast, the ''Ohka'' had a ...
''
kamikaze , officially , were a part of the Japanese Special Attack Units of military aviators who flew suicide attacks for the Empire of Japan against Allied naval vessels in the closing stages of the Pacific campaign of World War II, intending to d ...
planes. Accompanying her were nine empty oil tankers bound for Singapore, and the destroyers , , , and . Upon reaching Formosa and unloading her cargo, ''Ryūhō'' was among the targets of a major series of American carrier-based air raids all over the island. Twelve TBF Avengers attacked her, but none scored a hit, and ''Ryūhō''s gunners shot down one of them. ''Ryūhō'' departed for Japan on 2 January 1945 escorted by ''Isokaze''; when she arrived at Kure on 18 January, ''Ryūhō'' also gained the distinction of being the last Japanese aircraft carrier to venture outside the home waters of Japan. ''Ryūhō'' was attacked by
Task Force 58 The Fast Carrier Task Force (TF 38 when assigned to Third Fleet, TF 58 when assigned to Fifth Fleet) was a group of ships in World War II. It was the main striking force of the United States Navy in the Pacific War from January 1944 through th ...
aircraft on 19 March near Kure, suffering hits by three 500 lb bombs and two 5.5-inch rockets. The damage was severe: the flight deck bulged upward between the two elevators, the No. 1 boiler was punctured by a bomb fragment, the stern settled two meters into the water, and a raging fire broke out. Twenty crewmen were killed and thirty were wounded. Upon returning to Kure on 1 April, ''Ryūhō'' was considered to be a total loss. Moored as an abandoned hulk off of
Etajima , also called , ''Nomijima'', ''Nomi Island'', or is an island in Hiroshima Bay located in southwestern Hiroshima Prefecture, Japan. The mess with island name originates from the ancient (and possibly legendary) strait at now town . Geography T ...
, she was attacked by American aircraft again on 24 July and 28 July. She was struck from the
navy list A Navy Directory, Navy List or Naval Register is an official list of naval officers, their ranks and seniority, the ships which they command or to which they are appointed, etc., that is published by the government or naval authorities of a co ...
on 30 November 1945 and scrapped in 1946.


Notes


References

* * * * * * * * * * *


External links

* https://catalog.archives.gov/id/64490 – a film from around April to May 1946 showing damage to the ship {{DEFAULTSORT:Ryuho Ships built by Yokosuka Naval Arsenal 1933 ships Submarine tenders of the Imperial Japanese Navy Auxiliary depot ship classes Aircraft carriers of the Imperial Japanese Navy Second Sino-Japanese War naval ships of Japan World War II aircraft carriers of Japan Bombing of Kure Maritime incidents in March 1945