Tosa-class battleship

The Tosa-class battleships were ordered by the Imperial Japanese Navy in the early 1920s. The ships were larger versions of the preceding Nagato class, and carried an additional 41-centimeter twin-gun turret. 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. The hull of the second ship, Kaga, was converted into an aircraft carrier of the same name. She took part in the attack on Pearl Harbor on 7 December 1941 and the invasion of Rabaul in the Southwest Pacific in January 1942.

About Tosa-class battleship in brief

The Tosa-class battleships were two dreadnoughts ordered by the Imperial Japanese Navy in 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. 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. She took part in the attack on Pearl Harbor on 7 December 1941 and the invasion of Rabaul in the Southwest Pacific in January 1942. She was sunk during the Battle of Midway in 1942. The Tosa class became the basis for a much larger battleship, designated A-127, with nearly twice as much armor as the Nagato-class ships. It was designed to achieve the same speed as the older ships, to allow them to maneuver together as a tactical formation. This design was accepted on 27 March 1918 and became the Tosa Class battleships, which would have been 231 meters long at full load and 09,000 meters at the waterline. The first ship was scuttled in the Bungo Channel before it was completed, and was used in experiments testing the effectiveness of its armor scheme before being scrapped in 1921.

The second ship was built in lieu of Mutsu, but was scrapped before she was actually laid down. The IJN believed that a modern battle fleet of eight battleships and eight armored cruisers was necessary for the defense of Japan; the government ratified that idea in 1907. This policy was the genesis of the Eight-Eight Fleet Program, the development of a cohesive battle line of sixteen capital ships less than eight years old. In 1911, it restarted the program with orders for the Fusō-class super dreadnougts and the Kongō- class battlecruiser. By 1915, the IJn was halfway to its goal and wanted to order four more super dreadNoughts. The Diet rejected the plan and authorized only the dreadnought Nagato and two battle cruisers in the 1916 budget. In 1917, Captain Yuzuru Hiraga, superintendent of shipbuilding and the naval architect in charge of the fundamental design of the ships, presented a heavily modified version of the ship to the Navy. He proposed to angle the belt armor outwards to improve its resistance to horizontal fire, and to thicken the lower deck armor and the torpedo bulkhead. He estimated that the ship would displace about a million yen more. These changes would have considerably delayed the ship’s completion and were rejected by the Navy’s Ministry of the Navy, but were later accepted by the Japanese government as his design.

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