Tosa-class battleship

Tosa-class battleship. The Tosa class was a pair of planned fast battleships for the Imperial Japanese Navy during the early 1920s. Intended as successors to the preceding Nagato-class battleship, they were designed to compete with new American and British capital ships like the Colorado-class battleship and the G3 battlecruiser. Both vessels were cancelled and scrapped incomplete under the terms of the Washington Naval Treaty, though one hull was used extensively for testing.

Design and description

The design, developed under the leadership of naval constructor Yuzuru Hiraga, represented a significant evolution from the Nagato-class battleship. Primary armament consisted of ten 41 cm (16.1 in) guns mounted in five twin turrets, a layout that increased firepower over the Nagato-class battleship's four twin turrets. Protection was formidable, with a main armored belt 280 mm thick and deck armor up to 100 mm, designed to withstand fire from contemporary battleships like the American Colorado-class battleship. Propulsion from twelve Kampon boilers driving Brown-Curtis turbines was intended to produce a top speed of 26.5 knots, blending the firepower and protection of a dreadnought with the speed approaching a battlecruiser. The design directly influenced subsequent Japanese capital ship projects, including the never-built Kii-class battleship and the Number 13-class battleship.

Construction and cancellation

Construction of both ships began in early 1920; *Tosa* was laid down at the Mitsubishi Shipyard in Nagasaki on 16 February, while *Kaga* was started at the Kawasaki Shipyard in Kobe on 19 July. Work progressed steadily until the signing of the Washington Naval Treaty in February 1922, which imposed strict limits on capital ship tonnage for signatories including Japan, the United Kingdom, and the United States. Under Article II of the treaty, both incomplete hulls were designated for scrapping. *Tosa* was used as a target for shelling and torpedo tests in 1924 before being scuttled in the Bungo Channel in 1925. The hull of *Kaga* was saved from immediate destruction and was later converted into the aircraft carrier *Kaga*, which would see extensive service in the Second Sino-Japanese War and the early stages of the Pacific War before its sinking at the Battle of Midway.

Planned ships

Only two vessels of the class were planned. The lead ship was to be named *Tosa*, after the historical Tosa Province on Shikoku. The second was named *Kaga*, after the former Kaga Province on Honshu. In the Imperial Japanese Navy's naming convention, battleships were traditionally named after ancient provinces. Had they been completed as battleships, they would have formed a powerful new division within the Combined Fleet, likely assigned to the First Fleet alongside the Nagato-class battleship and the older Ise-class battleship. Their cancellation freed resources and slipways that were eventually used for other major warships, most notably the construction of the aircraft carrier *Akagi*.

In popular culture

The Tosa class, as unbuilt "what-if" capital ships, occasionally appears in historical alternate history literature and discussions. They feature in several naval simulation and strategy video games, such as the *Warship Gunner* series and the globally popular online game *World of Warships*, where they are represented as high-tier vessels. The class is also a subject of interest in detailed technical books on the Imperial Japanese Navy, including volumes by historians like Hans Lengerer and Lars Ahlberg, and is frequently analyzed in comparative studies of treaty-era naval architecture alongside designs like the American South Dakota-class battleship (1920) and the British N3-class battleship. Category:Battleship classes Category:Cancelled battleships of Japan Category:Washington Naval Treaty