Like the trio of 'Taiyo' class ships that preceded them, the Junyo and her sister Hiyo of the 'Junyo' class were useful conversions from Nippon Yusen Kaisha liners that had been designed from the outset with this procedure in mind. Where the earlier ships had undergone rebuilding at a late stage, the larger Taiyo' class ships were taken in hand before launching, both being in the water by June 1941, over five months before the Pacific War began, and completed in mid-1942.
As they had been designed as passenger liners, they had considerable freeboard and could accommodate two hangars, albeit of restricted headroom. They also had respectably-sized flight decks, measuring 210.2m by 27.3 m (689.6 ft by 89.6 ft), and two centreline elevators, but suffered badly from the combination of their low mercantile speed and lack of catapults.
The two ships were the first Japanese carriers to incorporate a funnel as part of the island, though it was of strange aspect, canted outward at a sharp angle. Except for the nevercompleted Italian Aquila, this pair of carriers were the largest ever converted from mercantile hulls.
Junyo's 53 aircraft could have had a decisive effect at Midway but the ship was engaged in the rather fruitless Aleutians diversion. At Santa Cruz in October 1942 her aircraft damaged the battleship USS South Dakota and a cruiser, playing also a significant role in the sinking of the carrier USS Hornet. The two sisters operated together as Kakuta's Carrier Division Two but, at the battle of the Philippine Sea, where Ozawa took on the vastly superior force of Mitscher's TF 58, the partnership was broken, the Junyo being heavily damaged by bombing and Hiyo sunk after blowing up. The Hiyo had been struck by two torpedoes and was probably lost from the detonation of a build-up of vapour from leaking Avgas tanks.
The Junyo, newly repaired, was torpedoed in December 1944 and, though she was not sunk, she never re-entered service, surviving to be one of the very few Japanese naval ships of any size to fall eventually into American hands.
Specification 'Junyo' class Displacement: 24,500 tons standard and 26,950 tons full load Dimensions: length 219,2 m (719 ft 2 in); beam 26.7 m (87 ft 7 in); draught 8.2 m (26 ft 11 in) Propulsion: geared steam turbines delivering 56,000 shp (41760 kW) to two shafts Speed: 25 knots Armament: 12 127-mm (5-in) DP and 24 25-mm AA guns Aircraft: 53 Armour: none Complement: about 1,220