Myōkō-class cruiser
The Myōkō-class cruisers were a series of four heavy cruisers built for the Imperial Japanese Navy in the late 1920s. Three were lost during World War II.
The ships of this class displaced 11,633 tons, were long, and were capable of steaming at. Their main armament were ten 20 cm/50 3rd Year Type naval guns in five twin turrets which were complemented by a heavy torpedo armament; at the time, this was the heaviest armament of any cruiser class in the world. They were also the first cruisers the Japanese Navy constructed that exceeded the limit set by the Washington Naval Treaty.
Design
The Myōkō class displaced, with a hull design similar to the preceding. The displacement was substantially more than the designed 2/3 trial displacement of, a consequence of the demand to put as much as possible on a hull limited by the Washington Naval Treaty, and were likely unintentional as it adversely affected the seekeeping qualities and endurance of the class. They were long with a beam of, and a draft of. Propulsion was by 12 Kampon boilers driving four sets of single-impulse geared turbine engines, with four shafts turning three-bladed propellers propelling the ship to. Design endurance was 8,000 nautical miles however the increased weight issues reduced it to 7,000.Protection was superior to the preceding Aoba-class and accounted for about 16 percent of trial displacement. A side belt that ran along of the ship's length and armored deck protected the magazine and machinery spaces and protected the turret barbettes; however, the turrets only had 25mm splinter protection and the bridge was unarmored. Following innovations pioneered in Yubari, the armor belt was made an integral part of the hull structure to reduce weight. A torpedo bulkhead consisting of two plates with a total thickness of extended inwards from the bottom of the armor belt and curved to meet the bottom of the double hull. It was calculated that it was sufficient to withstand an explosion of of TNT.
As originally constructed, the class was armed with a main battery of ten 20 cm/50 3rd Year Type naval guns mounted in 5 twin turrets, the heaviest armament of any heavy cruiser in the world at the time. Secondary armament initially were 12 cm/45 10th Year Type dual purpose guns in six single mounts. Short-range Anti-aircraft defense was provided by two 7.7mm machine guns. Torpedo armament was unusually heavy compared to the cruisers of other nations at the time, with 12 carried in fixed single launchers inside the hull. They were also equipped with a single aircraft catapult and aircraft for scouting purposes.
Modernizations
The class was modernized twice before the outbreak of the Pacific War. The first modernization program, carried out between 1934–36, was the most extensive. The main armament was upgraded to the 2 GÔ versions and the 120mm guns replaced with eight 12.7 cm/40 Type 89 dual purpose guns in twin mounts. The single catapult was replaced with an aircraft deck that could accommodate three aircraft and two catapults. The fixed torpedo tubes in the hull were removed and two quadruple launchers carrying the Type 93 Long Lance torpedo were installed under the aircraft deck. The torpedo bulges were extended to increase stability. The modifications added 680 tons of displacement and reduced speed to. Anti-aircraft protection was increased to eight 13mm machine guns in two quadruple mounts.The second modernization in 1939 added an additional two quadruple torpedo launchers and enhanced light anti-aircraft armament with the introduction of the Type 96 25mm gun. The aircraft catapults were upgraded to handle heavier floatplanes and the torpedo bulges were enlarged to increase stability.
The class would receive upgrades during the Second World War to reflect the growing threat of aircraft in the form of numerous Type 96 25mm gun and air and surface search radar, Myōkō eventually receiving 52 25mm autocannons in various single, double, and triple mounts. The two aft quadruple torpedo mounts were removed in 1944 to allow for the growing number of anti-aircraft armament.
Ships in class
The ships in the class were:| Name | Builder | Laid | Launched | Commissioned | Fate |
| Yokosuka Navy Yard | 25 October 1924 | 16 April 1927 | 31 July 1929 | Captured 21 September 1945 at Singapore. Scuttled in the Strait of Malacca, 8 July 1946 | |
| Kure Navy Yard | 26 November 1924 | 15 June 1927 | 26 November 1928 | Sunk 4 November 1944 in Manila Bay by aircraft from | |
| :ja:三菱重工業長崎造船所|Mitsubishi Nagasaki Shipyard | 16 March 1925 | 24 March 1928 | 25 April 1929 | Sunk 16 May 1945 in the Strait of Malacca by the Royal Navy 26th Destroyer Flotilla | |
| :ja:川崎造船所|Kōbe-Kawasaki Shipbuilding Yard | 11 April 1925 | 22 April 1928 | 20 August 1929 | Sunk 8 June 1945 in Bangka Strait by the submarine |