Amagi-class battlescruiser

The Amagi-class battlescruiser is one of the workhorses of the Japanese Navy's Eight-Eighth Fleet program. On the basis of the hull of Nagao class battleship, a double-mounted main gun is added. The turret layout is similar to that of Kaga class battleship. It can be said that it is the Kaga class light-armored and fast type, with reduced armor. The secondary guns are all on the same deck. The Amagi class's hypothetical opponents are the U.S. Navy's six Lexington class battleships.
The Amagi class battleship cruiser is largely a version of the Kaga class battleship cruiser, with a speed of up to 30 knots as more boilers are fitted. The Amagi class is identical in firepower to the previously launched Kaga-class battleships, with five dual-mounted "40cm" turrets. The difference between the two types of battleships lies in the armor design. The armor protection of the Amagi class is significantly weaker than that of the Kaga class. Not only does the Amagi class lack the main armor belt of the Kaga class, but the maximum thickness of the horizontal armor is only 4 inches, and the protection of the gun mount and turret is much weaker than that of the Kaga class.


More importantly, the Amagi class was significantly inferior to the Kaga class in terms of the area covered by the maximum thickness of the armor belt and the total weight of the armor. However, the Japanese Navy intended the Amagi class to be a battle-cruiser, so the design neglected survivability without much criticism
. On 6 December 1920, the first and second ships of the Amagi class, the Akagi, laid their keels simultaneously at Yokosuka and Wu Harbor Naval Works. But the construction of the No. 3 Atago and No. 4 Kaohsiung was delayed until late November and early December of the following year.

Performance data for this class:

Full load displacement: 47,000 tons
Length: 251.8 m
Waterline length: 234.7 m
Maximum broadside width: 30.8 m
Maximum draft: 9.4 m

Maximum output of main engine: 131200 horsepower
Maximum design speed: 30 knots, 14 knots range 8000 nautical miles
Protection: side main armor belt 10 inches, bow and stern 1.85 inches to 3 inches, main horizontal armor 1.3 inches to 3.9 inches, main turret frontal 9 inches and surrounding 6 inches, gun base 11 inches to 9 inches, control tower 14 inches
Armament: Main guns: five dual 410 mm 45x diameter main guns
Secondary gun: 140 mm 50 diameter side gun profile type secondary gun 20
Anti-aircraft guns: four 80mm 40x diameter anti-aircraft guns
Lightning Strike: Eight 610 mm torpedo tubes

1920 Washington disarmament conference held, the United States, Britain, Japan, France, Italy five major naval countries of the warship tonnage, firepower and gross tonnage
The limit. Using the 525,000 tons of the British and American navies as the standard, the five countries built their capital ships and cruisers in a 10:10:6:3.5:3.5 ratio. Battleships must not exceed 35,000 tons in tonnage and their main guns must not exceed 14 inches (356mm) in caliber. According to this standard, the Nagato class battleships belong to the type prohibited by the treaty. The great powers demanded that Japan terminate the construction of the battleships of this class and destroy the launched but unfinished battleships of the Luo 'ao. Under the strong attitude of Japan, the United States and Britain finally agreed that the first two Amagi ships (Amagi and Akagi) which were nearly completed could be converted into aircraft carriers, but the Kaga-class battleships must be destroyed.