Japanese aircraft carrier Ryūjō

The ship was fitted with two geared steam turbine sets with a total of 65,000 shaft horsepower (48,000 kW), each driving one propeller shaft, using steam provided by six Kampon water-tube boilers. Ryūjō had a designed speed of 29 knots (54 km/h; 33 mph), but reached 29.5 knots (54.6 km/h; 33.9 mph) during her sea trials from 65,270 shp (48,670 kW). 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.[7]

Starboard and overhead diagrams of Ryūjō

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 23.5 meters (77 ft 1 in) from the ship's stem, giving Ryūjō a distinctive open bow. The 156.5-meter (513 ft 5 in) flight deck was 23 meters (75 ft 6 in) 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 6,000 kg (13,000 lb) aircraft.[5] The ship's hangars were both 102.4 meters (335 ft 11 in) long and 18.9 meters (62 ft 0 in) wide, and had an approximate area of 3,871 square metres (41,667 sq ft).[8] Between them, they gave the ship the capacity to store 48 aircraft, but only 37 could be operated at one time.[5] After the Fourth Fleet incident, Ryūjō's 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 2 meters (6 ft 7 in).[6]

Aircraft were transported between the hangars and the flight deck by two elevators; the forward platform measured 15.7 by 11.1 meters (51.5 ft × 36.4 ft) and the rear 10.8 by 8.0 meters (35.4 ft × 26.2 ft).[8] 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.[5]

As completed, Ryūjō's 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.[7] When firing at surface targets, the guns had a range of 14,700 meters (16,100 yd); they had a maximum ceiling of 9,440 meters (30,970 ft) 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.[9] Twenty-four anti-aircraft (AA) Type 93 13.2 mm Hotchkiss machine guns were also fitted, in twin[7] and quadruple mounts.[6] Their effective range against aircraft was 700–1,500 meters (770–1,640 yd). 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.[10]

During the carrier's 1934–1936 refit, two of the 12.7-centimeter (5.0 in) mountings were exchanged for two twin-gun mounts for license-built Hotchkiss 25 mm Type 96 light AA guns,[6] resulting in a reduction of approximately 60 long tons (61 t) of top-weight that improved the ship's overall stability.[5] 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."[11] These 25-millimeter (0.98 in) guns had an effective range of 1,500–3,000 meters (1,600–3,300 yd), and an effective ceiling of 5,500 meters (18,000 ft) 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.[12] The machine guns were replaced during a brief refit in April–May 1942 with six triple-mount 25-millimeter (0.98 in) AA guns.[6]

Overhead view of Ryūjō at sea around 1935

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.[Note 1] Her air group had not changed, but four of each type of aircraft were spares. Ryūjō's initial airstrike consisted of 13 B5Ns escorted by nine A5Ms with a smaller airstrike later in the day by two B5Ns and three A5Ms. They accomplished little, destroying two Consolidated PBY seaplanes on the ground for the loss of one B5N and one A5M. The ship covered the landing at Davao on 20 December and her B5Ns attacked a British oil tanker south of Davao.[16] In January 1942 her aircraft supported Japanese operations in the Malay Peninsula.[14]

In mid-February 1942, Ryūjō's aircraft attacked ships evacuating from Singapore, claiming eight ships damaged, three burnt, and four sunk. They also covered convoys carrying troops to Sumatra. The ship was unsuccessfully attacked by several Bristol Blenheim light bombers of No. 84 Squadron RAF on 14 February. 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. Follow-on attacks the same day were also unsuccessful. Two days later, B5Ns destroyed HNLMS Van Ghent, a Dutch destroyer that had run aground in the Gaspar Strait and been abandoned on 14 February.[17] The carrier sailed to Saigon, French Indochina, the next day and arrived on 20 February. A week later she was assigned to cover the convoy taking troops to Jakarta, Java.[14] 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.[18] Six other B5Ns bombed the port of Semarang, possibly setting one merchantman on fire.[14]

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.[14] On 1 April, while the 1st Air Fleet was starting its raid in the Indian Ocean, Malay Force, consisting of Ryūjō, six cruisers, and four destroyers, left Burma on a mission to destroy merchant shipping in the Bay of Bengal. B5Ns damaged one freighter on 5 April before the force split into three groups. Ryūjō's aircraft bombed the small ports of Cocanada and Vizagapatam on the southeastern coast of India the next day, doing little damage, in addition to claiming two ships sunk and six more damaged during the day. The carrier and her escorts, the light cruiser Yura and the destroyer Yūgiri, claimed to have sunk three more ships by gunfire. All together, Malay Force sank 19 ships totaling almost 100,000 gross register tons (GRT),[19] before reuniting on 7 April and arriving at Singapore on 11 April. A week later, her B5Ns were detached for torpedo training and the ship arrived at Kure on 23 April for a brief refit.[14]

The newly commissioned carrier Jun'yō joined Carrier Division 4, under the command of Kakuta, with Ryūjō on 3 May 1942. They formed the core of the 2nd Carrier Strike Force, part of the Northern Force, tasked to attack the Aleutian Islands, an operation planned to seize several of the islands to provide advance warning in case of an American attack from the Aleutians down the Kurile Islands while the main body of the American fleet was occupied defending Midway. Ryūjō's air group now consisted of 12 A6M2 Zeros and 18 B5Ns,[20] plus two spares of each type. The ship transferred to Mutsu Bay on 25 May and then to Paramushiro on 1 June before departing the same day for the Aleutians.[14]

At dawn on 3 June, she launched 9 B5Ns, escorted by 6 Zeros, to attack Dutch Harbor on Unalaska Island. 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. A second airstrike was launched later in the day to attack a group of destroyers discovered by aircraft from the first attack, but they failed to find the targets. One Zero from Ryūjō from the second strike was damaged by a Curtiss P-40 and crash landed on the island of Akutan. The aircraft, later dubbed the Akutan Zero, remained largely intact and was later salvaged by the U.S. Navy and test flown. On the following day, the two carriers launched another airstrike, consisting of 15 Zeros, 11 D3As, and 6 B5Ns, which successfully bombed Dutch Harbor. Shortly after the aircraft were launched, the Americans attacked the carriers, but failed to inflict any damage. A Martin B-26 Marauder bomber and a PBY were shot down by Zeros, and a Boeing B-17 Flying Fortress bomber was shot down by flak during the attack.[21]

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. She arrived at Kure on 13 July for a refit and was transferred to Carrier Division 2 a day later.[14]

The disabled Ryūjō (top center) under attack from high altitude by B-17 bombers on 24 August 1942. The destroyer Amatsukaze (lower left) is moving away from Ryūjō at full speed and the destroyer Tokitsukaze (faintly visible, upper right) is backing away from the bow of Ryūjō in order to evade the B-17s' falling bombs.

The American landings on Guadalcanal and Tulagi on 7 August caught the Japanese by surprise. The next day, Ryūjō was transferred to Carrier Division 1 and departed for Truk on 16 August together with the other two carriers of the division, Shōkaku and Zuikaku. Her air group consisted of 24 Zeros and nine B5N2s.[22] Admiral Isoroku Yamamoto, commander-in-chief of the Combined Fleet, ordered Truk to be bypassed and the fleet refueled at sea after an American carrier was spotted near the Solomon Islands on 21 August.[23] 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. This Detached Force was commanded by Rear Admiral Chūichi Hara in Tone.[24]

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. Four Grumman F4F Wildcat fighters from Marine Fighter Squadron VMF-223 on combat air patrol (CAP) near Henderson Field spotted the incoming Japanese aircraft around 14:20 and alerted the defenders. 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. Nine of the Zeros strafed the airfield while the B5Ns bombed it with 60-kilogram (132 lb) bombs to little effect. The Americans claimed to have shot down 19 aircraft, but only three Zeros and three B5Ns were lost, with another B5N forced to crash-land. Only three Wildcats were shot down in turn.[25]

Around 14:40, the Detached Force was spotted again by several search aircraft from the carrier USS Enterprise; the Japanese ships did not immediately spot the Americans. 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. Two more Zeros reinforced the patrol shortly after 15:00, just in time to intercept two more searching Avengers, shooting down one. 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. They found the carrier shortly afterward and attacked. They hit Ryūjō three times with 1,000-pound (454 kg) bombs and one torpedo; the torpedo hit flooded the starboard engine and boiler rooms. No aircraft from either Ryūjō or Saratoga were shot down in the attack.[26]

The bomb hits set the carrier on fire and she took on a list from the flooding caused by the torpedo hit. Ryūjō turned north at 14:08, but her list continued to increase even after the fires were put out. The progressive flooding disabled her machinery and caused her to stop at 14:20. The order to abandon ship was given at 15:15 and the destroyer Amatsukaze moved alongside to rescue the crew. 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 with the loss of seven officers and 113 crewmen.[14] Fourteen aircraft that she had dispatched on raids returned shortly after Ryūjō sank and circled over the force until they were forced to ditch. Seven pilots were rescued.[27]