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Design A-150 battleship

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Design A-150.jpg
An impression of a A-150-class battleship by Richard Allison
Class overview
Name: A-150
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: 263.0 m (863 ft) (est.)
Beam: 38.9 m (128 ft) (est.)
Propulsion: Unknown
Armor: Possibly a 460 mm (18.1 in) side belt

Design A-150, also known as the Super Yamato class,[A 1] was a design for a class of battleships for the Imperial Japanese Navy (IJN). Begun in 1938–1939, the design was mostly complete by 1941. However, after the start of the Pacific War in December 1941, all work on Design A-150 was halted so that the demand for other types of warships could be met and no ship was ever laid down. Historians William H. Garzke and Robert O. Dulin have argued that Design A-150 would have been the "most powerful battleships in history" because of the massive size of their main battery of six 51-centimeter (20.1 in) guns as well as numerous smaller-caliber weapons.[1]

Background & design[edit]

Initial plans for the A-150 battleships called for eight or nine 510 mm guns in double or triple turrets. The successful construction of a 48-centimeter (18.9 in) gun in 1920–1921 made the Japanese confident that a 51 cm weapon could be built. In addition, a top speed of 30 knots (56 km/h; 35 mph) was desired so that the class would be faster than 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 90,000 long tons (91,000 t); it was felt that ships of this size would be "too large and too expensive".[1]

Initial design studies were undertaken after the completion of plans for the Yamato class (1938–1939), although they focused on a ship with a displacement nearer to that of the Yamatos.[2] As the Japanese expected that the Americans would be able to ascertain the true characteristics of that class (namely the principal armament of 46-centimeter (18.1 in) guns), the use of 51 cm guns was vital in keeping with Japan's policy of individual ships' superiority over their American counterparts; the A-150s were meant to counter the United States' reply to the Yamatos.[1]

Plans were "essentially completed" sometime in 1941;[2] however, much like the documents relating to the Yamato class,[3][4] most papers and all plans relating to the class were destroyed at the end of the war, meaning that the full specifications of the ships are not known.[1] It is known the ships would have had greater firepower than the Yamato class with a main battery of six 51 cm guns in three twin-turrets and a secondary armament of "many" 10-centimeter (3.9 in) dual-purpose guns.[2] The displacement was to be similar to the Yamato class, which was around 70,000 metric tons (69,000 long tons).[5] The side armor belt was probably going to be 46 cm thick.[6] This was so large that steel mills in Japan were incapable of manufacturing it; instead, two layers of armor plates" were going to be used, which would have been much less effective than just one single plate.[2]


Although details of the smaller armament planned for the ships are not given in sources, a main battery of six 45-caliber 51 cm guns in three turrets was definitely planned. These would have been the largest ever fitted to a capital ship, dwarfing the 46 cm guns mounted on the Yamato class.[7] By 1941, one—possibly two—of the 51 cm guns were being constructed at the Kure Naval Arsenal and detailed designs of their turrets were drawn up. The turrets would have weighed 2,780 tonnes (2,740 long tons) and each gun would have massed 227 metric tons (223 long tons). They would have had a total length of 23.56 meters (77 ft 4 in) and the bore length was to have been around 22.84 meters (74 ft 11 in). The armor-piercing shells would have weighed 1,950 kg (4,300 lb).[8]

A secondary battery of "many" 65-caliber 10 cm Type 98 guns was being considered, although this was not final. The guns had a maximum elevation of +90° which gave them an effective ceiling of 11,000 meters (12,030 yd) or 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 the resulting wear of the barrels reduced their life to only about 350 rounds. They were able to fire 15–19 rounds per minute.[9]


With war on the horizon in early 1941, all design work was diverted from battleships—even though the A-150s' design was virtually complete—so that a demand for "aircraft carriers, cruisers, and smaller ships"[1] could be met. Even though no work was being done on them, two ships of Design A-150, provisionally designated as Warships Number 798 and 799, were projected in a 1942 building program. 798 was to be built in the same dock as Shinano, while 799 was to be built in Kure in the same dock as Yamato after the fourth ship in the class, Warship Number 111, was launched. Both of the ships' keels were supposed to be laid in late 1941 or early 1942, launched in 1944–1945, and finished in 1946–1947. However, the war's turn against the Japanese after the Battle of Midway meant that the need for ships other than battleships never abated.[2]

See also[edit]


  1. ^ Although called the "Super Yamato class" by some, Design A-150 was an entirely new design that had little in common with the earlier Yamato-class battleships.[1]


  1. ^ a b c d e f Garzke and Dulin (1985), p. 85
  2. ^ a b c d e Garzke & Dulin (1985), pp. 85–86
  3. ^ Muir (1990), p. 485
  4. ^ Skulski (1989), p. 8
  5. ^ Breyer (1973), p. 330
  6. ^ Gardiner & Chesneau (1980), p. 178
  7. ^ Garzke & Dulin (1985), pp. 85, 88
  8. ^ Lacroix & Wells, p. 755
  9. ^ Lacroix & Wells, p. 626


  • Breyer, Siegfried (1973). Battleships and Battle Cruisers, 1905–1970. Garden City, New York: Doubleday. OCLC 702840. 
  • Garzke, William H. & Dulin, Robert O. (1985). Battleships: Axis and Neutral Battleships in World War II. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-101-3. OCLC 12613723. 
  • Gardiner, Robert & Chesneau, Robert, eds. (1980). Conway's All the World's Fighting Ships, 1922–1946. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-913-8. OCLC 18121784. 
  • Lacroix, Eric & Wells, Linton (1997). Japanese Cruisers of the Pacific War. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-311-3. 
  • Muir, Micheal (October 1990). "Rearming in a Vacuum: United States Navy Intelligence and the Japanese Capital Ship Threat, 1936–1945". The Journal of Military History. Society for Military History. 54 (4): 485. ISSN 1543-7795. JSTOR 1986067. OCLC 37032245. 
  • Skulski, Janusz (1989). The Battleship Yamato. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-019-X. OCLC 19299680.