Design A-150 battleship

	Artist's impression of an A-150-class battleship
Class overview
Name	A-150
Builders	Yokosuka Naval Arsenal; Kure Naval Arsenal;
Operators	Imperial Japanese Navy
Preceded by	Yamato class
Succeeded by	None
Planned	2
Completed	0
Cancelled	2
General characteristics
Type	Battleship
Displacement	Approximately 70,000 long tons (71,000 t)
Length	263 m (862 ft 10 in) (est.)
Beam	38.9 m (127 ft 7 in) (est.)
Propulsion	Unknown
Armament	3 × twin 51 cm (20.1 in) guns; "Many" 10 cm (3.9 in) dual-purpose guns;
Armor	Possibly a 45.7 cm (18 in) side belt; Turret: 80 cm (31 in) (face); 29.5 cm (11.6 in) (roof);

Design A-150,^[A] popularly known as the Super Yamato class,^[B] was a planned class of battleships for the Imperial Japanese Navy. In keeping with longstanding Japanese naval strategy, the A-150s would have carried six 51-centimeter (20.1 in) guns to ensure their qualitative superiority over any other battleship they might face. These would have been the largest guns ever carried aboard a capital ship.

Design work on the A-150s began after the preceding

laid down

, and many details of the class' design were destroyed near the end of the war.

Background and design

In the 1930s, the Japanese government began a shift towards an

ultranationalist militancy. Planners envisioned an empire stretching from Japan to the resource-rich European colonies in Southeast Asia, and defensible islands in the Pacific Ocean (the Greater East Asia Co-Prosperity Sphere). The extensive distances involved, and the likelihood of this expansion leading to a confrontation with the United States, led the Japanese to build and maintain a large fleet that could seize and hold onto these territories.^[2]^[3] The U.S. posed a particular problem for Japan, as it possessed significantly greater industrial power,^[4] and several leading members of the United States Congress had pledged "to outbuild Japan three to one in a naval race".^[5]

The Imperial Japanese Navy had recognized since at least 1896 that the country could not outproduce its potential opponents, and therefore insisted that its ships had to be more powerful than foreign equivalents. It established this qualitative lead at various times over the next 40 years, with the

Kongo-class battlecruisers just before World War I, the Nagato-class battleships at the end of that war, and the Yamato-class battleships in the 1930s.^[6] The A-150s were designed according to that doctrine to continue their qualitative superiority in battleships over their most likely opponents, the United States and Great Britain.^[1]

Early conceptions for what would become the A-150 battleships called for eight or nine 51-centimeter guns in double or triple turrets, as the successful construction of a 48-centimeter (18.9 in) gun in 1920–1921 made the Japanese confident that such a large weapon could be built. The designers hoped to give the ships a top speed of 30 knots (56 km/h; 35 mph), which would give them a comfortable margin over the American 27-knot (50 km/h; 31 mph) North Carolina-class battleships. However, these grand specifications were curtailed when tests culminated in a ship that had a displacement of some 91,000 metric tons (90,000 long tons); it was felt that ships of this size would be "too large and too expensive".^[1]

Formal design studies began in 1938–1939. They initially focused on a ship closer to the displacement of the preceding Yamato class, on which plans had just been completed, albeit one mounting six 51-centimeter guns.^[7] As the Japanese expected that the Americans would ascertain the true characteristics of the Yamato class—especially its primary armament of 46-centimeter (18.1 in) guns, which would become the largest naval weapons in use in the world—they hoped that the 51-centimeter guns would outperform any American response to the Yamato's smaller guns.^[1]

Specifications

Plans for the A-150s were finished in early 1941, for most intents and purposes. However, these were destroyed at the end of the war, along with most of the other documentation relating to the class.^[7] The general destruction of records and Japan's extensive efforts (before and during the war) to keep any information about the ships out of the hands of foreign nations severely limited the amount of information on the ships available to historians.^[8]^[9] For these reasons the A-150's exact specifications are uncertain.^[1] The displacement was to be similar to the Yamato class, which was around 70,000 metric tons (69,000 long tons),^[10] and the belt armor was probably going to be 45.7 centimeters (18 in) thick.^[11] This was so large that steel mills in Japan were incapable of manufacturing it. Instead, two layers of armor plates would have been used, despite its reduced effectiveness as compared to a single plate of the same total thickness.^[7] Similarly, the turret-face armor would have been 80 centimeters (31 in) thick in two layers. The roof armor would have consisted of a single plate 29.5 centimeters (11.6 in) thick.^[12]

Armament

The design of the A-150s called for a

armor-piercing shells would have weighed 1,950 kg (4,300 lb).^[14]

The composition of the A-150's secondary armament is not fully known. Historians Eric Lacroix and Linton Wells have written that Japanese designers were considering mounting a large number of 65-caliber 10-centimeter (3.9 in) Type 98 dual-purpose guns, though this was not final. These guns had a maximum elevation of +90°, which gave them an effective ceiling of 11,000 meters (12,030 yd) and a horizontal range of 14,000 meters (15,311 yd). They fired 13-kilogram (29 lb) projectiles at a muzzle velocity of 1,030 m/s (3,400 ft/s), although resulting wear on the barrels reduced their designed lifespan to only about 350 rounds. They were able to fire 15–19 rounds per minute.^[15]

Construction

As war with the United States became increasingly likely over the

launched. The ships would then have been finished in 1946–1947, but the war's turn against the Japanese after the Battle of Midway meant that the need for ships other than battleships never abated.^[7]

Notes

^ In Japanese, the name for this planned ship class is Chō Yamato-gata senkan (超大和型戦艦). These ships were never given formal names.
^ Although called the "Super Yamato class" by some historians, Design A-150 was entirely new, having little in common with the earlier Yamato-class battleships.^[1]

References

^ ^a ^b ^c ^d ^e ^f ^g Garzke & Dulin (1985), p. 85
^ Willmott (1999), p. 32
^ Schmo (2004), pp. 42–43
^ Willmott (1999), p. 22
^ Thurston, Elliott (2 January 1935). "Fear is the Real Cause of Navy Treaty End". The Washington Post. p. 7.
^ Evans & Peattie (1997), p. 59
^ ^a ^b ^c ^d Garzke & Dulin (1985), pp. 85–86
^ Muir (1990), p. 485
^ Skulski (1989), p. 8
^ Breyer (1973), p. 330
^ Sturton (1980), p. 178
^ Lengerer & Ahlberg (2019), p. 398
^ Garzke & Dulin (1985), pp. 85, 88
^ Lengerer & Ahlberg (2019), p. 396
^ Lacroix & Wells (1997), p. 626