page_title: Tosa-class battleship
section_title: Cancellation and fates
hierarchical_section_title: Tosa-class battleship / Cancellation and fates
caption_attribution_description: 日本語: 加賀　日本海軍航空母艦。大改装後の写真。煙突から噴出しているのは航空機の運用への影響をさけるため煤煙を冷却するための海水。English: Imperial Japanese Navy Carrier Kaga: photo taken after her massive refitting. Its smokestack is directed downwards to extinguish the smoke with seawater.
context_page_description: The Tosa-class battleships were two dreadnoughts ordered as part of the "Eight-Eight" fleet for the Imperial Japanese Navy during the early 1920s. The ships were larger versions of the preceding Nagato class, and carried an additional 41-centimeter twin-gun turret. The design for the class served as a basis for the Amagi-class battlecruisers.
  Both ships were launched in late 1921, but the first ship, Tosa, was cancelled in accordance with the terms of the Washington Naval Treaty before it could be completed, and was used in experiments testing the effectiveness of its armor scheme before being scuttled in the Bungo Channel. The hull of the second ship, Kaga, was converted into an aircraft carrier of the same name. The carrier supported Japanese troops in China during the Second Sino-Japanese War of the late 1930s, and took part in the attack on Pearl Harbor on 7 December 1941 and the invasion of Rabaul in the Southwest Pacific in January 1942. The following month her aircraft participated in a combined carrier airstrike on Darwin, Australia, during the Dutch East Indies campaign. She was sunk during the Battle of Midway in 1942.
context_section_description: Construction of both ships began in 1920, but the 1922 Washington Naval Treaty intervened, mandating the cancellation of all capital ships being built. Work stopped on the two Tosa-class battleships on 5 February 1922. After being stricken on 1 April 1924, Her guns were turned over to the Imperial Japanese Army for use as coastal artillery; two of her main-gun turrets were installed on Tsushima Island and near Busan, Korea. The rest of her guns were placed in reserve and ultimately scrapped in 1943. Tosa's incomplete hull was used to test her armor scheme against long-range naval gunfire, aerial bombs, mines, and torpedoes. Two of the shells fired at her fell short, but deeply penetrated her hull through the thin armor of the torpedo bulge below the waterline armor belt. This sparked an interest in optimizing underwater performance of Japanese shells that culminated in production of the Type 91 armor-piercing shell. Conversely, the IJN took measures to defend against shells of this type when reconstructing its existing battleships during the 1930s, as well as in the designs of the Yamato-class battleships and the heavy cruisers of the Mogami and Tone classes. Tosa's torpedo defense system proved able to defeat 200 kg (440 lb) torpedo warheads, but not larger 350 kg (770 lb) ones. After the conclusion of the tests, the ship was scuttled by opening her Kingston valves on 9 February 1925 in 650 m (2,130 ft) of water in the Bungo Channel after the demolition charges failed to detonate.
  The battlecruiser Amagi, which was being converted to an aircraft carrier under the terms of the treaty, was wrecked in the Great Kantō earthquake in 1923 and rendered unusable. As a result, Kaga, which was originally slated to be scrapped under the terms of the Washington Naval Treaty (Chapter I, Article IX), was converted in Amagi's stead. No work took place until 1925 as new plans were drafted and earthquake damage to the Yokosuka Naval Arsenal was repaired. Although the ship was commissioned on 31 March 1928, she did not join the Combined Fleet (Rengō Kantai) until 30 November 1929.
  Much like the converted Amagi-class battlecruiser Akagi, Kaga was fitted with two flying-off decks "stepped down" from a flight deck that extended two-thirds of the ship; in theory, this allowed planes to take off directly from the hangars while other planes landed on the top. As aircraft became heavier during the 1930s, they required longer distances to get airborne and the lower flight decks became useless. Kaga's 1935 reconstruction removed the lower two decks and extended the top flight deck to the bow. As completed, the ship had two main hangar decks and a third auxiliary hangar with a total capacity of 60 aircraft.
  Kaga was provided with a heavy gun armament in case she was surprised by enemy cruisers and forced to give battle, but her large and vulnerable flight deck, hangars, and other features made her more of a target in any surface action than a fighting warship. Carrier doctrine was still evolving at this time and the impracticability of carriers engaging in gun duels had not yet been realized. The ship was armed with ten 20 cm/50 3rd Year Type guns: one twin-gun turret on each side of the middle flight deck and six in casemates aft. Kaga's waterline armored belt was reduced from 280 to 152 mm (11.0 to 6.0 in) during her reconstruction and her deck armor was also reduced from 102 to 38 mm (4.0 to 1.5 in). The carrier displaced 26,900 long tons (27,300 t) at standard load, and 33,693 long tons (34,234 t) at full load, nearly 6,000 long tons (6,100 t) less than her designed displacement as a battleship. This reduction in her displacement increased her speed to 27.5 knots (50.9 km/h; 31.6 mph) and gave her a range of 8,000 nautical miles (15,000 km; 9,200 mi) at 14 knots (26 km/h; 16 mph).
  In 1933–35 Kaga was rebuilt to increase her top speed, improve her exhaust systems, and adapt her flight decks to more modern, heavier aircraft. After the reconstruction, the ship displaced 38,200 long tons (38,800 t) at standard load, better boilers gave her a top s
caption: Kaga after her 1930s reconstruction
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