Hosho

Hosho underway shortly after completion, December 1922.

Design

First considered in the 1918 Naval shipbuilding programme, Hosho was to be built as a seaplane carrier, akin to HMS Campania. Although the keel was laid down, this plan was soon revised after Japanese naval attachés observed the desirable characteristics of HMS Furious, such as close to 30 knots of speed and more than 35 onboard aircraft. Not to be left behind, Hosho was proposed to become a full aircraft carrier with similar capabilities.

As Japan’s first purpose-built carrier, her design was based of a converted cruiser hull, which limited her tonnage to under 8,000 tonnes and no armour to speak of. For propulsion, eight boilers fed to two turbines, generating 30,000 shaft horsepower, which in speed trials pushed the vessel to 26 knots. For a ship of her size, she had an impressive range of above 8,000 nautical miles. Unique to Hosho, she carried an onboard gyrostabilizer to reduce rolling during rough seas.

As a purpose-built carrier, Hosho had a full, unobstructed flight deck that was slightly tilted down to aid aircraft acceleration. Originally built, Hosho had an island superstructure on the starboard side, which held the bridge and aircraft control center. Hosho’s two hangars were designed to house different aircraft. The smaller, forward hanger housed fighters, while the rear, larger hangar housed bombers. Originally built, Hosho’s aircraft complement was 15 aircraft, split between fighters and torpedo bombers.

For close-in defence, Hosho was armed with four 140mm naval guns, which were considered to be a heavy battery for a ship of this tonnage, at that time. Carrier doctrine was non-existent at this time, and so designers considered artillery combat a possibility with aircraft carriers. Conversely, not much was considered for anti-aircraft defense; she was originally armed with two 80mm high-angle guns, positioned near the back of the ship.

Throughout her carrier, Hosho underwent some modifications. The most significant change was in 1924, when the island was deleted and the funnels were moved to the side of the ship, in order to provide an unobstructed flight deck. Furthermore, the funnels could swivel to lie horizontally, to eject gasses away from the deck. Her AA armament, seen to be ineffective was replaced with various numbers of 25mm cannons throughout the War. Finally, in late 1944, Hosho’s flight deck was extended to make landings easier.

Aircraft Carrier Hosho was laid down in 16 December 1920 by the Asano Shipbuilding Company, and launched 13 November 1921. She was completed at the Yokosuka Naval Arsenal on 10 January 1922.

Service

Commissioned into the Imperial Japanese Navy on 27 December 1922, Hosho spent the first few years of her service life laying the foundation and groundwork for the budding Japanese carrier doctrine. This is when her first major reconstruction occurred, in order to better accommodate aircraft handling operations.

With tensions rising in China in the early 1930s, Hosho – along with the rest of the Third Fleet – was stationed near Shanghai and covered Japanese operations through February and March. She was the first IJN ship to conduct aerial operations; mainly in the way of air-superiority, bomber escort, and airfield raids.

From late 1935 to early 1936, Hosho was spending time in the dockyards after suffering damage from a typhoon while undergoing a training sortie with the Fourth Fleet. The entire first half of the flight deck had to be rebuilt and reinforced after the original one collapsed and had to be cut away. Also while in the dockyards, measures were taken to decrease her top weight; funnels permanently swiveled horizontally, aircraft crane and upper deck aviation fuel tanks were deleted.

Hosho was stationed back in China with the Third Fleet after the Second Sino-Japanese War commenced in the late 1930s. During the summer of 1937, Hosho’s air groups were tasked with bomber interdiction and close-air support to assist the Imperial Japanese Army operations near Shanghai. By autumn of 1937, Hosho, along with Ryujo, operated off the south China coast conducting further raids against Chinese airfields.

By the winter, she was relegated to reserve status and transferred her aircraft to Ryujo. Although out-dated, the Navy realized her service life could be extended as a training carrier, and as such modifications were made by late 1939.

When the Second World War commenced, Hosho was pressed into service as secondary air-defence for the Main Body of Battleships for the Combined Fleet for not only the raid on Pearl Harbor, but Midway as well. With the Japanese defeat, Hosho returned to mainland Japan to resume training duties.

In order to service the larger and more modern aircraft that were coming into service in late 1944, Hosho had her flight deck enlarged, and new aircraft handling gear installed. She dutifully trained new pilots until the end of the war.

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  Hosho’s external appearance in 1922.

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  Hosho’s external appearance in 1924.

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  Hosho’s external appearance in 1936.

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  Hosho’s external appearance in 1945.

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  Hosho stationed in Shanghai.

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  Kaga and Hosho during the Second Sino-Japanese War.