Amagi-class battlecruiser

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The Amagi class was a planned group of four Japanese battlecruisers from the early 1920s, named Amagi, Akagi, Atago, and Takao. They were basically longer versions of the Tosa class, with lighter armor but more powerfully engineered for high speed. They would have carried ten 41 cm guns in five turrets and could reach about 30 knots, with a cruising range of around 8,000 nautical miles at 14 knots.

Displacement would have been about 41,217 tonnes standard and up to 47,000 tonnes full load. The ships were designed to be about 252 meters long, with a beam of 30.8 meters and a draft of 9.5 meters, powered by four shafts and a large set of boilers to drive their turbines. Their main armor belt was planned around 250 mm thick, with deck armor of about 95 mm and conning towers up to 360 mm in places.

Armament would have included a strong secondary battery of sixteen 14 cm guns, anti-aircraft guns, and eight 61 cm torpedo tubes in addition to the main battery. The class was intended to be a balanced mix of firepower, speed, and range.

However, the 1922 Washington Naval Treaty limited new capital ships and allowed existing hulls under construction to be converted into aircraft carriers, up to a 27,000-ton limit. Amagi and Akagi were chosen for conversion. The Great Kantō earthquake in 1923 damaged Amagi so badly that it could not be repaired, and Amagi was scrapped in 1924. Atago and Takao were canceled in 1924 and broken up.

Instead, the incomplete Tosa-class battleship Kaga was converted into a carrier to replace Amagi. Akagi was rebuilt as an aircraft carrier, completed in 1927, and later served with distinction as part of the Kido Butai. Akagi took part in the attack on Pearl Harbor and fought at Midway, where it was sunk.