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

Design A-150, popularly known as the Super Yamato class, 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 Yamato class in 1938–1939 and was mostly finished by early 1941, when the Japanese began focusing on aircraft carriers and other smaller warships in preparation for the coming conflict. No A-150 would ever be laid down, and many details of the class' design were destroyed near the end of the war.

Background and design

See also: Empire of Japan during the Later Shōwa period

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. The U.S. posed a particular problem for Japan, as it possessed significantly greater industrial power, and several leading members of the United States Congress had pledged "to outbuild Japan three to one in a naval race".

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. 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.

After the design process finished with an Improved A-140F6 variant design slated for Shinano and Warship No. 111 (see: Yamato Class) of the 4th Programme, there was a new design effort in 1938/1939 to have a new heavier Yamato-class variant that mounted 8-9 of the 510 mm (20.1 in) guns and be protected from the same weapon at a range of 20-30km. The Japanese Admiralty preferred the twin gun turret designs, in part due to the A-140F6 Kai, or the Improved variant of the 5th Programme (Starting with Warship No. 797 - never laid down), already planning to support three turrets of the type by this point; although the design had not been finalized as of yet. Also, the 20.1 inch gun had already been developed and produced in 1935 for trials involving both the 18.1 inch guns mounted to Yamato and the future 20.1 inch Naval Guns. This design (A-150) was originally part of the 6th Programme that the late designer Fujimoto conceived and the other designers followed in the Yamato Project (A-140) of the mid 1930s.

The Admiralty pushed for a 30 knot top speed initially; however this would increase displacement up to 100,000 tons. A lot of mounting options were considered including triple mount turrets of 510 mm (20.1 in) or even quadruple mounts. Although quadruple mounts were impressive on paper, it proved to be too much as the increase in displacement (way beyond the bounds of 100,000 tons) and decrease in speed (less than 27 knots) made it much more impractical. In the end, before the end of World War II, three designs were considered, one with four triple mount turrets of 510 mm (20.1 in) and a speed of 27 knots at 100,000 tons, a further variant with four dual mount 510 mm (20.1 in) guns and a speed of 27 knots at 85,000 tons and a final sub-variant of the previous that could cruise along at 30 knots at 100,000 tons. Definitely, it was a trade off to get more of these giant cannons mounted on the ship. Secondary Armament on the ships varied as to whether or not they would retain the 2 triple 155 mm (6.1 in) guns of the Improved A-140F6 Slated for Shinano and Warship No. 111. After heated debate it was rumored to be decided to either keep them on the higher tonnage designs or to do away with them on faster, lower tonnage designs. Although general characteristics were vague on how many 100 mm (3.9 in) 60 Caliber guns were mounted, many artist drawings, in reference to incomplete plans, called for 16 dual mount 100 mm (3.9 in) 60 Caliber guns with 8 per side between main tower and secondary tower. It was also possible that they would mount many dual mount 25 mm (1.0 in) AA cannons (at least 36 dual mounts) onboard in addition to the impressive suite of 100 mm (3.9 in) guns.

It was proposed that 4 ships would be built in this class, however in the meantime, during World War II; multiple things happened that closed the door on this design project forever. Not only would the fourth hull of the Yamato class be broken up and reused for other construction projects as well as Shinano (the third ship of the Yamato class) was converted into an Aircraft Carrier, but also the 4 ships of this class were never ordered. The sobering truth was that the Yamato class as built and in her 1945 configuration after her refit were pushing the limits of Japanese Industry and drydock capacity as the Super Yamato designs would need a new slipway even larger and longer than Yamato and her sisters. In fact, the sheer size of the A-150 design would be impossible to construct very quickly with the quality of steel the Japanese had that would be required for a ship of the A-150’s size and weight. It was also rumored that armor plates would have to be attached in layers in order to achieve the desired thickness on some surfaces. As such, the Design Department and Admiralty refocused their efforts on improving the existing A-140F6 design (Yamato), and the Improved upgraded variant intended for Shinano and Warship No. 111 of the 4th Programme, culminating into the A-140F6 “Kai” (This designation is not official. it is only used as a way to differentiate from the Improved design with 18.1 inch guns that was slated for Shinano and Warship No. 111 from the one armed with 20.1 Inch guns slated for Warship No. 797 and 798 of the 5th Programme), keeping to the existing dimensions of Yamato, Musashi and Shinano instead of bigger designs. As such, in a way, the A-150 plan was, in its final form, the A-140 Kai or Improved design of the 5th Programme with 6 510 mm (20.1 in) guns in dual mounts and 12 dual turrets of 100 mm (3.9 in) guns; retaining the triple 155 mm (6.1 in) guns forward and aft of the superstructure. The loss of Yamato and Musashi, along with the Admiralty’s switching of priorities to Aircraft Carrier Production (as evidenced by Shinano's Conversion into an Aircraft Carrier) instead of Battleship Construction halted all progress on any further Yamato Class Battleships and their future variants including the A-140F6 Kai and the A-150 Project in General.

Specifications and Armor

Plans for the A-150 design were finished in early 1941 (Post Project shift to the A-140 Kai), 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. 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. For these reasons the A-150's exact specifications are mostly uncertain. The displacement in some sources was rumored to be similar to the Yamato class, which was around 70,000 metric tons (69,000 long tons),. In reality it might have been propaganda to throw allied intelligence off about the new ships like they did for the Yamato Class (Project A-140), or otherwise in reference to the new focus for an improvement to the existing Yamato class battleships being built or already in service. More modern sources compiled from the designers' accounts of the project put the tonnage (before the switch to the A-140 Kai as a focus of the A-150 Project) to a range between 85,000 metric tons (84,000 long tons) and 100,000 metric tons (98,000 long tons). As these are theoretical numbers from never built designs, the actual tonnage may have been close to 150,000 metric tons (150,000 long tons) had they been built. The belt armor was rumored to be 45.7 centimetres (18 in) thick, however this was never verified due to lack of information and the designers' accounts of the project not specifying the thickness. What is known from these accounts, of the designers that worked on the project, is that the Turret Faces were to be 800 mm (31.5 in) thick while their roofs 295 mm (11.6 in) thick. The displacement and the high armor thickness was so much of a problem for Japanese industry at the time that steel mills in Japan were incapable of manufacturing it in one piece. 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. Speed rumors range between 27 knots of the original Yamato Class to over 30 knots, however this confusion is mainly due to the priority shift in the project midway through development and the realized impracticality of such a large design. Although no powerplant is known for certain, it is probably safe to assume the A-150 Variants would be powered by Steam Geared Turbines like Yamato and her sisters. Although hybrid Turbine/Diesel or full diesel arrangements were explored in the A-140 Yamato Project, it was discovered that the Marine Diesel Engines produced domestically were less powerful and less reliable than initially thought. This spurred the push to have the Yamato be powered fully by a Steam Geared Turbine Powerplant which would have most likely not changed by the time of the A-150 design's construction.

Armament

The design of the A-150s called for a main battery of between eight and nine 45-caliber 51-centimeter (20.1 inch) guns in four twin or triple turrets. These would have been the largest ever fitted to a capital ship, dwarfing the 46-centimeter guns mounted on the Yamato class, and were a key factor in historians William H. Garzke and Robert O. Dulin's argument that the A-150s would have been the "most powerful battleships in history". At least one 20.1 inch gun was already built and tested, at least as early as 1935; though priority was given to the 18.1 inch guns as the Yamato class was given priority. More likely the prototype 20.1 inch gun was tested by 1940 or early 1941. The turrets would have weighed 2,780 metric tons (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). After Priority shifted to the A-140F6 Kai slated for the 5th Programme after discovering the impracticality of the higher tonnage designs, the new design called for a 1 to 1 replacement of the Yamato Class Main Armament from 9 18.1 inch guns in 3 triple mount turrets to 6 45-caliber 51-centimeter (20.1 Inch) guns in three twin mount turrets. This replacement was to be carried out as a refit on all Yamato Class ships currently in service and all future ships starting with Warship Number 797 or 798 (the two ships slated to have their keels laid after Shinano and Warship No. 111).

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. Many artist interpretations show 12-16 of these guns mounted as part of either the original large tonnage designs before the shift to the A-140 Kai or the Kai upgrade program for the Yamato Class when priority shifted. This particular improvement was slated for the Improved A-140F6 design which was intended for Shinano when she was built. This switch was a 1 to 1 switch from 12 of the 127mm or 5 inch twin mounts of the Yamato and Musashi 1944/1945 design respectively to 12 65-caliber 10-centimeter (3.9 in) Type 98 dual-purpose guns. Although the Kai Program and the previous improved variant for Shinano and Warship No. 111 did keep the remaining 2 triple 155 mm (6.1 in) guns, commonly available on Japanese light cruisers, whether they would have ended up being mounted to the A-150 designs is in heavy speculation. Some artist interpretations have them, specifically to high tonnage designs, while most others omit these turrets. The reason was that these guns were poorly armored and only capable of protecting the crew from shell splinters due to being 25mm or around 1 inch thick all around. In fact, the Improved A-140F6 variant design, intended for Shinano and Warship No. 111 during their initial construction, called for an extra 25mm to be added to increase the protection to around 2 inches or 50mm as these turrets were plucked directly off of former Japanese Light Cruisers that were rearmed as Heavy Cruisers. Some artist interpretations have the 25mm AA turrets from Yamato in dual mounts represented (at least 36 of those turrets), while others have them removed completely. In reality, many nations, including Japan studied and found out that the 20mm variants of anti-aircraft weapons were too short range and generally insufficient to shoot down aircraft as the war progressed. As such, many nations explored adding more weapons closer to 40mm that could blow most planes out of the sky in only a few hits.

Construction

As war with the United States became increasingly likely over the Second Sino-Japanese War, and particularly after the Japanese seizure of French Indochina in mid-1940, all design work on battleships was diverted in early 1941—even though the A-150's design was nearly complete—in order to focus on higher-priority warships like aircraft carriers and cruisers. None of the A-150s were ordered, however two ships of the 5th Programme (After the A-140 Kai design was finished for this program), provisionally designated as Warships Number 797 and 798, were projected in a 1942 building program. Under this plan, 797 would have been built in the same dock as Shinano, while 798 would be built in Kure in the same dock as Yamato after a fourth Yamato-class ship was launched (Warship No. 111). The ships would have 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.

Bibliography

• Breyer, Siegfried (1973). Battleships and Battle Cruisers, 1905–1970. Garden City, New York: Doubleday. OCLC 702840.
• Evans, David & Peattie, Mark R. (1997). Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887–1941. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-192-7.
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• 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.
• Lacroix, Eric & Wells, Linton (1997). Japanese Cruisers of the Pacific War. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-311-3.
• Muir, Malcolm (October 1990). "Rearming in a Vacuum: United States Navy Intelligence and the Japanese Capital Ship Threat, 1936–1945". The Journal of Military History. 54 (4). Society for Military History: 485. doi:10.2307/1986067. ISSN 1543-7795. JSTOR 1986067. OCLC 37032245.
• Schom, Alan (2004). The Eagle and the Rising Sun: The Japanese-American War, 1941–1943, Pearl Harbor through Guadalcanal. New York: W. W. Norton. ISBN 0-393-04924-8. OCLC 50737498.
• Skulski, Janusz (1989). The Battleship Yamato. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-019-X. OCLC 19299680.
• Willmott, H.P. (1999). The Second World War in the Far East. London: Cassell. ISBN 0-3043-5247-0. OCLC 59378558.

Further reading

• Lengerer, Hans & Ahlberg, Lars (2019). Battleship Tosa Demolition Tests to the Modified Yamato Class. Capital Ships of the Imperial Japanese Navy, 1868–1945. Vol. 3. Zagreb: Despot Infinitus. ISBN 978-953-8218-57-6.