These ships were really conversions of passenger liners. Commishioned in 1940, Hiyo and Junyo could hold 53 aircraft each and were kept in reserve for most of the early part of the war, as auxillary carriers, in the event that they were needed to augment the main fleet, or if the big ships were incapible of accomplishing their mission, these would be used. Such an event happened on June 6, 1942, when all carriers in Nagumo's 1st air fleet were destroyed. At the time the sister ships were busy raiding Attu and Dutch Harbor. Hiyo was sunk in 1944, and Junyo was heavially damaged on the way home from Leyte. She survived the war and was scrapped in 1947.

Displacement: 28,300 tons full load

Dimensions: 706 x 87.5 x 26.5 feet/215 x 26.7 x 8 meters

Extreme Dimensions: 719.5 x ?? x 26.5 feet/219 x ?? x 8 meters

Propulsion: Steam turbines, 6 boilers, 2 shafts, 56,250 shp, 25.5 knots

Crew: 1187-1224

Armor: 1 inch over machinery

Armament: 6 dual 5/40 DP, 24 25 mm AA

Aircraft: 53

Concept/Program: Large liners built under the "Shadow Program" and intended for easy conversion to carriers. They were an intermediate type between heavy and light fleet carriers: as large as the heavies, but too slow for effective fleet operations. These vessels were classed as auxiliaries until 31 July 1942, when they were reclassified as warships.

Design/Conversion: Taken over prior to completion. Reworked from the main deck up with dual hangars (restricted in height to reduce topweight), full length flight deck, large island, bulged hull, etc. Sea speed was 22-23 knots and the low hangar clearances were a serious hindrance.

Modifications: Both received an additional 26 25 mm AA in 1943; Junyo carried up to 76 25 mm by 1944. Operational: Both saw varied service through 1944. Departure from Service/Disposal: Hiyo sunk 1944; Junyo rendered inoperable in 1944.

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