The Nachi: First true IJN heavy cruisers
The heavy cruisers of the Nachi class laid down between 1924 and 1925 and completed in 1928-29, were at the very limits of the Washington Treaty, yet they managed to bear a five turret arrangement never seen on a ship of this type before, and imposing to the IJN new standard, not followed internationally but coherent with Japanese retirement of the league of nations.
This feat consisted of being able to stack five twin turrets for 8-in/203 mm guns and 12 torpedo tubes on a cruiser more than 200 meters long, but which ultimately displaced only the 10,000 tons required by the treaty. They could reach 35.5 knots without excessive power either. The secret laid partly in their amazing width/lenght ratio almost unchanged from the Aoba, about the same 12/1. Their protection was greatly improved however with an inner armoured citadel and a triple hull plus reinforced coss-sections and a reduced but reinforced bulkhead. In fact, the final tonnage as for 1941 was 11,000 tons.
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1930s et 1940s refit
In 1934-36, their single 120 mm single mounts gave way to new 127 mm (5 in) twin turrets, their fixed torpedo tubes replaced by quadruple rotating banks, while the AA was reinforced by four additional 13.2 mm machine guns and two catapults were installed on the sides to launch reconnaissance floatplanes. In 1940-41 there was a second overhaul concerning the masts and superstructures, the addition of 8 x 25 mm AA guns and especially two new quadruple torpedo tubes on the flanks, for a total of 16, a record for a cruiser, but in the typical trend of aggressiveness of the Japanese tactics at the time. This forced to add imposing bulges in order to safeguard their stability.
The Nachi class in action
In operations, these four ships, the IJN Nachi, Myoko, Ashigara and Haguro proved formidable combatants, very actively employed, and which defeated all their American, British and Dutch opponents until 1943. The Myoko was apparently the only one to have been camouflaged. These Nachi class cruisers participated in the battle of Leyte, where the Nachi, in the confusion and fury of the attacks, collided and seriously damaged the Mogami.
Shortly before this battle, their AA armament had reached fifty-two 25mm guns, at the cost of removing two banks of torpedo tubes. They survived the battle of Samar (Leyte), the Nachi being sunk in November 1944 off Manila by USN air attacks, while IJN Myoko, already badly damaged in Leyte, was finished off by a torpedo from USS Bergall in December 1944.
She sank in shallow waters in the Strait of Malacca, and her wreck was dynamited in 1946 to allow trade to resume. The IJN Haguro and Ashigara were sunk respectively in May and June 1945, one by the torpedoes of British destroyers off Penang during the reconquest of Malaysia, while the second was torpedoed by British submarine HMS Trenchant in the Bangka Strait.
Myoko, camouflaged in 1944.
Displacement 13,000 t. standard -14,740 t. Full Load
Dimensions 203.76 m long, 20.60 m wide, 5.66 m draft
Propulsion 4 propellers, 4 turbines, 12 boilers, 130,000 hp.
Top speed 34 knots
Armour from 100 to 25 mm
Armament 10 guns of 152 (5 × 2), 8 guns of 12, 8 of 25 AA, 12 mitt. 13.2 mm AA, 16 TLT 610 mm (4 × 4), 3 aircraft