Ryūjō ( "Prancing Dragon") was a light aircraft carrier built for the Imperial Japanese Navy (IJN) during the early 1930s. Small and lightly built to exploit a loophole in the Washington Naval Treaty of 1922, she proved to be top-heavy and only marginally stable and was back in the shipyard for modifications within a year of completion. With her stability improved, Ryūjō returned to service and was employed in operations during the Second Sino-Japanese War.
During World War II, she provided air support for operations in the Philippines, Malaya, and the Dutch East Indies, where her aircraft participated in the Second Battle of the Java Sea. During the Indian Ocean raid in April 1942, the carrier attacked British merchant shipping. Ryūjō was next in the Battle of Dutch Harbor, the opening battle of the Aleutian Islands campaign, in June 1942. She was sunk by American carrier-based aircraft in the Battle of the Eastern Solomons on 24 August 1942.
Design Ryūjō was planned as a light carrier of around standard displacement to exploit a loophole in the Washington Naval Treaty of 1922 that carriers under standard displacement were not regarded as "aircraft carriers".See: Washington Naval Treaty, Chapter II, Part 4, DefinitionsPreston, p. 132; Lengerer, p. 129 While Ryūjō was under construction, Article Three of the London Naval Treaty of 1930 closed the above-mentioned loophole; consequently, Ryūjō was the only light aircraft carrier of her type to be completed by Japan.; See Part 1, Article 3, Paragraph 1.
Ryūjō had a length of overall.Sturton, p. 180 with a beam of and a draft of . She displaced at standard load and at normal load. Her crew consisted of 600 officers and enlisted men.Jentschura, Jung & Mickel, p. 45
To keep Ryūjōs weight to 8,000 metric tons, the hull was lightly built with no armor; some protective plating was added abreast the machinery spaces and magazines. She was also designed with only a single hangar, which would have left an extremely low profile (there being just of freeboard amidships and aft). Between the time the carrier was laid down in 1929 and launched in 1931, the Navy doubled her aircraft stowage requirement to 48 in order to give her a more capable air group. This necessitated the addition of a second hangar atop the first, raising freeboard to . Coupled with the ship's narrow beam, the consequent top-heaviness made her minimally stable in rough seas, despite the fitting of Sperry active stabilizers. This was a common flaw amongst many treaty-circumventing Japanese warships of her generation.Brown 1977, p. 17
The Tomozuru Incident of 12 March 1934, in which a top-heavy torpedo boat capsized in heavy weather, caused the IJN to investigate the stability of all their ships, resulting in design changes to improve stability and increase hull strength. Ryūjō, already known to be only marginally stable, was promptly docked at the Kure Naval Arsenal for modifications that strengthened her keel and added ballast and shallow torpedo bulges to improve her stability. Her funnels were moved higher up the side of her hull and curved downward to keep the deck clear of smoke.Parshall, Tully & Casse
Shortly afterward, Ryūjō was one of many Japanese warships caught in a typhoon on 25 September 1935 while on maneuvers during the "Fourth Fleet Incident." The ship's bridge, flight deck and superstructure were damaged and the hangar was flooded. The forecastle was raised one deck and the bow was remodelled with more flare to improve the sea handling. After these modifications, the beam and draft increased to and respectively. The displacement also increased to at standard load and at normal load. The crew also grew to 924 officers and enlisted men.
Machinery The ship was fitted with two geared steam turbine sets with a total of , each driving one propeller shaft, using steam provided by six Kampon water-tube boilers. Ryūjō had a designed speed of , but reached during her sea trials from . The ship carried of fuel oil, which gave her a range of at . The boiler uptakes were trunked to the ship's starboard side amidships and exhausted horizontally below flight deck level through two small funnels.Brown 1977, p. 18
Flight deck and hangars
Ryūjō was a flush-decked carrier without an island superstructure; the navigating and control bridge was located just under the forward lip of the flight deck in a long glassed-in "greenhouse", whilst the superstructure was set back from the ship's stem, giving Ryūjō a distinctive open bow. The flight deck was wide and extended well beyond the aft end of the superstructure, supported by a pair of pillars. Six transverse arrestor wires were installed on the flight deck and were modernised in 1936 to stop a aircraft. The ship's hangars were both long and wide, and had an approximate area of .Peattie, p. 235 Between them, they gave the ship the capacity to store 48 aircraft, but only 37 could be operated at one time. After the Fourth Fleet incident, Ryūjōs bridge and the leading edge of the flight deck were rounded off to make them more streamlined. This reduced the length of the flight deck by .
Aircraft were transported between the hangars and the flight deck by two elevators; the forward platform measured and the rear . The small rear elevator became a problem as the IJN progressively fielded larger and more modern carrier aircraft. Of all the aircraft in front-line service in 1941, only the Nakajima B5N "Kate" torpedo bomber would fit, when positioned at an angle with its wings folded. This effectively made Ryūjō a single-elevator carrier and considerably hindered transfer of aircraft in and out of the hangars for rearming and refueling during combat operations.
Armament As completed, Ryūjōs primary anti-aircraft (AA) armament comprised six twin-gun mounts equipped with 40-caliber 12.7-centimeter Type 89 dual-purpose guns mounted on projecting sponsons, three on either side of the carrier's hull. When firing at surface targets, the guns had a range of ; they had a maximum ceiling of at their maximum elevation of +90 degrees. Their maximum rate of fire was 14 rounds a minute, but their sustained rate of fire was around eight rounds per minute.Campbell, pp. 192–193 Twenty-four anti-aircraft (AA) Type 93 13.2 mm Hotchkiss machine guns were also fitted, in twin and quadruple mounts. Their effective range against aircraft was . The cyclic rate was adjustable between 425 and 475 rounds per minute, but the need to change 30-round magazines reduced the effective rate to 250 rounds per minute.Campbell, p. 202
During the carrier's 1934–1936 refit, two of the mountings were exchanged for two twin-gun mounts for Hotchkiss 25 mm Type 96 light AA guns, license-built, resulting in a reduction of approximately of top-weight that improved the ship's overall stability. This was the standard Japanese light AA gun during World War II, but it suffered from severe design shortcomings that rendered it a largely ineffective weapon. According to historian Mark Stille, the weapon had many faults including an inability to "handle high-speed targets because it could not be trained or elevated fast enough by either hand or power, its sights were inadequate for high-speed targets, [and] it possessed excessive vibration and muzzle blast."Stille, p. 51 These guns had an effective range of , and an effective ceiling of at an elevation of +85 degrees. The maximum effective rate of fire was only between 110 and 120 rounds per minute because of the need to frequently change the fifteen-round magazines.Campbell, p. 200 The machine guns were replaced during a brief refit in April–May 1942 with six triple-mount AA guns.
Construction and service
Following the Japanese ship-naming conventions for aircraft carriers, Ryūjō was named "Prancing Dragon".Silverstone, p. 335 The ship was laid down at the Mitsubishi's Yokohama shipyard on 26 November 1929. She was launched on 2 April 1931, towed to Yokosuka Naval Arsenal on 25 April for fitting out, and commissioned on 9 May 1933 with Captain Toshio Matsunaga in command. While training in mid-1933, her initial air group consisted of nine Mitsubishi B1M2 (Type 13) torpedo bombers, plus three spares, and three A1N1 (Type 3) fighters, plus two spares. Matsunaga was relieved by Captain Torao Kuwabara on 20 October. After the Tomozuru Incident, the ship was reconstructed from 26 May to 20 August 1934.Tully & Casse
Captain Ichiro Ono assumed command on 15 November 1934 and Ryūjō became the flagship of Rear Admiral Hideho Wada's First Carrier Division. The following month the ship was chosen to evaluate dive-bombing tactics using six Nakajima E4N2-C Type 90 reconnaissance aircraft, six Yokosuka B3Y1 Type 92 torpedo bombers, and a dozen A2N1 Type 90 fighters. The reconnaissance aircraft proved to be unsuitable after several months' testing. Ryūjō participated in the Combined Fleet Maneuvers of 1935 where she was attached to the IJN Fourth Fleet. The fleet was caught in a typhoon on 25 September and the ship was moderately damaged. Ryūjō arrived at Kure on 11 October 1935 for repairs, modifications, and a refit that lasted until 31 May 1936. On 31 October Ono was relieved by Captain Shun'ichi Kira.
In mid-1936, the ship was used to evaluate a dozen Aichi D1A dive bombers and dive-bombing tactics. She also embarked at that time 24 A4N1 fighters, plus four and eight spare aircraft respectively. In September, Ryūjō resumed her role as flagship of First Carrier Division, now commanded by Rear Admiral Saburō Satō. Her air group now consisted of a mixture of B3Y1 torpedo bombers, D1A1 dive bombers and A2N fighters, but her torpedo bombers were transferred after fleet maneuvers in October demonstrated effective dive bombing tactics. Captain Katsuo Abe assumed command of the ship on 16 November.
The First Carrier Division arrived off Shanghai on 13 August 1937 to support operations of the Japanese Army in China. Her aircraft complement consisted of 12 A4N fighters (plus four spares) and 15 D1A dive bombers. The dive bombers attacked targets in and near Shanghai. The Japanese fighters had their first aerial engagement on 22 August when four A4Ns surprised 18 Curtiss Hawk III fighters from the Nationalist Chinese Air Force and claimed to have shot down six without loss. The following day, four A4Ns claimed to have shot down nine Chinese fighters without loss to themselves.Hata, Izawa & Shores, p. 144 The carriers returned to Sasebo at the beginning of September to resupply before arriving off the South China coast on 21 September to attack Chinese forces near Canton. Nine fighters from Ryūjō escorted a raid on the city and claimed six of the defending fighters. While escorting another raid later that day, the Japanese pilots claimed five aircraft shot down and one probably shot down. The dive bombers attacked targets near Canton until the ship sailed to the Shanghai area on 3 October. Her air group was flown ashore on 6 October to support Japanese forces near Shanghai and Nanking. Ryūjō returned home in November and briefly became a training ship before she was assigned to Rear Admiral Tomoshige Samejima's Second Carrier Division.
In February 1938 the ship replaced her A4N biplanes with nine Mitsubishi A5M "Claude" monoplane fighters. The division supported Japanese operations in Southern China in March–April and again in October. Captain Kiichi Hasegawa assumed command on 15 November 1939. Ryūjō was given a refit that lasted from December 1939 through January 1940 and became a training ship until November when she became the flagship of Rear Admiral Kakuji Kakuta's Third Carrier Division. Hasegawa was relieved by Captain Ushie Sugimoto on 21 June. The ship's air group then consisted of 18 Nakajima B5N torpedo bombers and 16 A5M4 fighters. When the First Air Fleet was formed on 10 April 1941, Ryūjō became flagship of the Fourth Carrier Division.
World War II