Japan's withdrawal from the international treaties limiting the size of warships at the end of 1936 enabled her constructors at last to design carriers that suited requirements. Under the 1937 Reinforcement Programme two more carriers were to be built, basically similar to the Hiryu but large enough to accommodate all that was required.
In the 'Shokaku' class all the earlier faults were remedied. Two catapults were provided, and a much larger hangar enabled aircraft capacity to be increased from 63 to 75. Even with a considerable increase in power (the most powerful machinery ever fitted in a Japanese warship) the two ships could achieve a range of nearly 10,000 miles (16000 km) as they carried 5,000 tons of fuel. Equally important, they were well armoured and carried a much heavier anti-aircraft armament than their predecessors. In most respects they were the best carriers in the world, being surpassed only by the later 'Essex' class, but like all Japanese carriers they suffered from vulnerable fuel systems. Not only were the fuel lines to the hangars and flight deck liable to be ruptured by explosions some distance away, but the fuel storage tanks were inadequately protected against shock.
Shokaku was begun at the end of 1937 and went to sea in August 1941, just two months before Pearl Harbor. Although she took part in the attack her aircrews were too inexperienced to do more than bomb the airfields on Oahu. With her sister Zuikaku she formed Carrier Division 5, and after their work-up early in 1942 they operated off Ceylon and New Guinea.
During the Battle of the Coral Sea Shokaku was damaged by a strike from the Yorktown; although she caught fire she was saved with some difficulty, and had to return to Japan for repairs. The worst casualties were, however, the loss of 86 aircraft and most of their aircrews, so that neither carrier could take part in the Battle of Midway. On 14 July they joined the new Carrier Division 1, with the light carrier Zuiho. In the Battle of the Eastern Solomons they damaged the Enterprise but again lost precious aircrew and aircraft. On 26 October the Shokaku was severely damaged by a divebomber strike from the Hornet.
During the Battle of the Philippine Sea on 19 June 1944 she was hit by three torpedoes from the submarine USS Cavalla, and an explosion from ruptured aviation fuel tanks subsequently sank her.
Specification Shokaku Displacement: 25,675 tons standard, 32,000 tons full load Dimensions: length 257.5 m (844 ft 9 in) overall; beam 26,0 m (85 ft 4 in); draught 8.9 m (29 ft 2 in) Machinery: 4-shaft geared steam turbines delivering 160,000 shp (119310kW) Speed: 34.2 knots Armour: belt 215 mm (8 Vä in); deck 170mm(63/4in) Armament: eight twin 127-mm (5-in) dual-purpose and 12 triple 25-mm AA guns Aircraft: 27 fighters, 27 dive-bombers and 18 torpedo-bombers Complement: 1,660 officers and men