|Preceded by:||Aoba class|
|Succeeded by:||Takao class|
|Displacement:||11,633 tons (standard load) 14,980 tons (full load)|
|Length:||204 m (669 ft) overall|
|Beam:||17 m (56 ft)|
|Draught:||5.8 m (19 ft)|
|Speed:||35.5 knots (40.9 mph; 65.7 km/h)|
|Range:||8,000 nmi (15,000 km) at 14 kn (16 mph; 26 km/h)|
|Aviation facilities:||1 catapult|
The ships of this class displaced 11,633 tons (standard), were 201 metres (659 ft) long, and were capable of steaming at 36 knots (67 km/h; 41 mph). 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 (10,000 ton) limit set by the Washington Naval Treaty.
The Myōkō class displaced 13,500 t (13,300 long tons), with a hull design similar to the preceding Aoba-class cruiser. The displacement was substantially more than the designed 2/3 trial displacement of 11,850 t (11,660 long tons), 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 203.8 metres (669 ft) long with a beam of 19.5 metres (64 ft), and a draft of 6.36 metres (20.9 ft). 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 35.5 knots (65.7 km/h; 40.9 mph). 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 102 mm (4 in) side belt that ran along 123 m (404 ft) of the ship's length and 35 mm (1.4 in) armored deck protected the magazine and machinery spaces and 76 mm (3 in) 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 29 mm (1.1 in) plates with a total thickness of 58 mm (2.3 in) 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 200 kg (441 lb) of TNT.
As originally constructed, the class was armed with a main battery of ten 200 mm (7.9 in) 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.
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 203 mm (8 in) 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 34 knots (63 km/h; 39 mph). 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:
|Myōkō (妙高)||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|
|Nachi (那智)||Kure Navy Yard||26 November 1924||15 June 1927||26 November 1928||Sunk 4 November 1944 in Manila Bay by aircraft from USS Lexington|
|Haguro (羽黒)||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|
|Ashigara (足柄)||Kōbe-Kawasaki Shipbuilding Yard||11 April 1925||22 April 1928||20 August 1929||Sunk 8 June 1945 in Bangka Strait by the submarine HMS Trenchant|
- Lacroix, Eric; Linton Wells (1997). Japanese Cruisers of the Pacific War. Naval Institute Press. ISBN 0-87021-311-3.
- Stille, Mark (2011). Imperial Japanese Navy Heavy Cruisers 1941-45. Osprey Publishing Ltd. ISBN 978-1-84908-148-1.
- Tamura, Toshio (2004). "Re: Japanese Cruiser Torpedoes". Warship International. XLI (4): 366–367. ISSN 0043-0374.
- Whitley, M J (1995). Cruisers of World War Two: An International Encyclopedia. London: Arms and Armour Press. ISBN 1-85409-225-1.
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