After the battle, the carrier resumed her training role in Japanese home waters for the duration of the conflict and survived the war with only minor damage from air attacks.

The plan was revised after reports were received from Japanese observers with the Royal Navy in Europe about the desirability to be able to land aircraft on the ship.

The ship was to be capable of 30 knots (56 km/h; 35 mph) and fitted with a forward flight deck, island and funnels amidships, and a large hangar aft.

Shortly thereafter based on observations of landing trials on Furious and HMS Argus, the world's first flush-decked aircraft carrier, Hōshō's flight deck design was revised in April 1919.

The island was removed and the funnels were moved to one side to create an unobstructed, full-length flight deck, and the ship was reclassified as an aircraft carrier.

Eight Kampon Type B water-tube boilers with a working pressure of 18.3 kg/cm2 (1,790 kPa; 260 psi) and a temperature of 138 °C (280 °F) provided steam to the turbines, although only four were oil-fired.

[9] To reduce rolling and increase stability for aircraft operations, a gyrostabilizer produced by the American Sperry Gyroscope Company was installed.

Low landing speeds of the time meant that aircraft had little difficulty in stopping, but their light weight made them vulnerable to wind gusts that could blow them over the side of the carrier, and the longitudinal wires helped to prevent that.

Hōshō was delayed by repeated design changes and late deliveries of equipment, pushing the commissioning date from March to 27 December 1922.

The island, tripod mast, and aircraft crane were removed since they partially obstructed the flight deck and obscured pilot visibility.

[21] Another reason for removal of the island was that the IJN found that it was too small and cramped to be of effective use in controlling air operations or conning the ship.

The lessons learned influenced the design and construction of Ryūjō and the subsequent conversions of battlecruiser Akagi and battleship Kaga into aircraft carriers.

Two days later, the two carriers sent some of their aircraft to Kunda Airfield where they flew ground attack missions in support of the Imperial Japanese Army.

Caught in a typhoon on 23 September, the carrier and a number of other Japanese ships were badly damaged in what was referred to as the "Fourth Fleet incident.

[29] While the Hōshō was at the dockyard between 22 November 1935 and 31 March 1936, her stability was improved; the forward flight deck's supports were reinforced and increased in number; the ship's AA guns, aircraft crane and upper deck aviation fuel tanks were removed; the funnels were fixed in the horizontal position with their mouths angled slightly downwards; the front sides of Hōshō's forward hangar and bridge were reinforced; and the ship's hull was reinforced in the vicinity of her rear hangar to increase her longitudinal strength.

[24] During the Sino-Japanese War, Hōshō rejoined the Third Fleet and supported land operations of the army in Central China in August 1937 with Ryūjō, later joined by Kaga.

Details of the activities of Hōshō's aircraft are scarce, but three of the ship's Nakajima A2N fighters shot down a Martin B-10 bomber on 25 July.

The Japanese pilots claimed to have shot down sixteen enemy aircraft and an additional probable loss during the day's fighting.

A later investigation determined on 23 December 1940 that she could not operate the latest aircraft types like the Mitsubishi A6M Zero, the Aichi D3A "Val", or the Nakajima B5N "Kate" in combat.

[34] Hōshō began the Pacific War in the Third Carrier Division assigned to the 1st Fleet under Vice Admiral Shirō Takasu.

[35] With the Main Body, Hōshō sortied from the Inland Sea on 7 December 1941 to provide distant cover for the carrier forces under Chūichi Nagumo which were attacking Pearl Harbor.

The battleship force turned back 300 nautical miles (556 km) east of Japan, but Hōshō became separated on 10 December due to radio silence restrictions while conducting anti-submarine air operations.

In order to recover the aircraft, however, the carrier and her three escorting destroyers had to steam east and therefore lost sight of the Main Body in the darkness.

The carrier was located by scout aircraft the next day 500 nautical miles (926 km) east of the Main Body and returned to port at Kure on 12 December.

[36] On 29 May 1942, Hōshō sortied from Japan with the rest of the fleet for the operation which resulted in the Battle of Midway, providing modest air protection, scouting, and anti-submarine support for the Main Body, now consisting of the battleships Yamato, Nagato, and Mutsu.

The observer aboard the aircraft also reported seeing survivors left behind on Hiryū so the destroyer Tanikaze was sent to unsuccessfully search for the wrecked carrier.

In this role, Hōshō shuttled back and forth between Kure and the Western Inland Sea, spending equal amounts of time at each location.

[14][19][Note 4] Hōshō was slightly damaged by a single bomb or aerial rocket hit when the Allies attacked Kure again on 24 July 1945.

Information is scarce on the extent of the ship's involvement in the action, but it appears the carrier's participation was minimal, as she embarked no aircraft at the time.

[19] In December 1945, Hōshō's overhanging flight deck at the bow was cut off to improve visibility from the bridge and her hangars were modified to carry more passengers.