Small and lightly built in an attempt 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 to address those issues within a year of completion.

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.

[5] To keep Ryūjō's 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.

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.

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.

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.

[7] 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 carried 2,490 long tons (2,530 t) of fuel oil, which gave her a range of 10,000 nautical miles (19,000 km; 12,000 mi) at 14 knots (26 km/h; 16 mph).

The boiler uptakes were trunked to the ship's starboard side amidships and exhausted horizontally below flight deck level through two small funnels.

[6] After the Fourth Fleet incident, Ryūjō's bridge and the leading edge of the flight deck were rounded off to make them more streamlined.

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.

[10] Twenty-four anti-aircraft (AA) Type 93 13.2 mm Hotchkiss machine guns were also fitted, in twin[8] and quadruple mounts.

[6] 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.

[15] Captain Ichiro Ono assumed command on 15 November 1934 and Ryūjō became the flagship of Rear Admiral Hideho Wada's First Carrier Division.

In September, Ryūjō resumed her role as flagship of First Carrier Division, now commanded by Rear Admiral Saburō Satō.

Ryūjō returned home in November and briefly became a training ship before she was assigned to Rear Admiral Tomoshige Samejima's Second Carrier Division.

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.

[15] The ship's assignment at the beginning of the Pacific War was to support the invasion of the Philippines, initially by attacking the American naval base at Davao, Mindanao, on the morning of 8 December.

The following day two waves of B5Ns, totaling 13 aircraft, attacked the British heavy cruiser Exeter, but managed only to damage the ship's Supermarine Walrus seaplane.

[15] Her aircraft participated in the Second Battle of the Java Sea on 1 March and six B5Ns sank the American destroyer Pope after it had been abandoned by its crew.

[15] Ryūjō arrived in Singapore on 5 March and the ship supported operations in Sumatra and escorted convoys to Burma and the Andaman Islands for the rest of the month.

One B5N crashed on takeoff but 6 of the B5Ns and all of the Zeros were able to make it through the bad weather, destroying two PBYs and inflicting significant damage on the oil storage tanks and barracks.

[22] Ryūjō arrived back at Mutsu Bay on 24 June, and departed for the Aleutians four days later to cover the second reinforcement convoy to Attu and Kiska Islands and remained in the area until 7 July in case of an American counterattack.

[24] At 01:45 on 24 August, Vice Admiral Chūichi Nagumo, commander of the Mobile Force, ordered Ryūjō and the heavy cruiser Tone, escorted by two destroyers, detached to move in advance of the troop convoy bound for Guadalcanal and to attack the Allied air base at Henderson Field if no carriers were spotted.

[25] Ryūjō launched two small airstrikes, totaling 6 B5Ns and 15 Zeros, beginning at 12:20 once the Diversionary Force was 200 nautical miles (370 km; 230 mi) north of Lunga Point.

Ten more Wildcats from VMF-223 and VMF-212 scrambled, as well as 2 United States Army Air Corps Bell P-400s from the 67th Fighter Squadron in response.

They launched three Zeros for a combat air patrol at 14:55, three minutes before two of the searching Grumman TBF Avenger torpedo bombers narrowly missed Ryūjō 150 meters (164 yd) astern with four 500-pound (227 kg) bombs.

In the meantime, the carrier USS Saratoga had launched an airstrike against the Detached Force in the early afternoon that consisted of 31 Douglas SBD Dauntlesses and eight Avengers; the long range precluded fighter escort.

The ships were bombed several times by multiple B-17s without effect before Ryūjō capsized about 17:55 at coordinates 06°10′S 160°50′E / 6.167°S 160.833°E / -6.167; 160.833 with the loss of seven officers and 113 crewmen.