By the latter years of the 1930s, the Imperial Japanese Navy was becoming more ambitious, leading to the designing and building of what would become known as the world’s most powerful battleship: the Super Yamato-class or, as designated by the IJN, the A-150. The project that ignited this was the IJN’s desire to counter the rising power of the United States Navy and to ensure that its dominance in the Pacific would be uncontested.
After 1936, with the withdrawal of Japan from the Second London Naval Treaty, there came a new stage in the design of warships by the IJN, this time directly grounded in the “Doctrine of Decisive Battle”. Under this doctrine, ships faster and more powerfully gunned than their American counterparts would deal a decisive blow to the U.S. fleet. The class, part of that program, was the Yamato class, featuring battleships with 460mm guns. Intelligence reports the following year, however, indicated that the U.S. Navy was contemplating warships with 18-inch guns, which led to Japan’s desire to design a more powerful vessel.
Preliminary design work for the A-150, intended to be a ship with a displacement similar to that of the ships of the Yamato-class but armed with 510mm main battery guns, began in the fiscal years 1938-1939 in what the Japanese hoped would be the ultimate answer by one combatant nation to another. Indeed, one would expect that the number of possible configurations of the A-150 should have included those armed with six 510mm guns in three twin-gun turrets and those armed with eight 510mm guns in four twin-gun turrets.
In the six-gun version, the usual displacement was approximated to 64,000 tons. With a waterline length of 262 meters and a maximum width of 38.9 meters. Its power plant comprised 12 boilers and four Kanpon turbines producing 150,000 hp which forced a designing speed of 27knts, a cruising range that is estimated at 7,200 miles at 16knots.
THE eight-gun version had a standard displacement of 86,730 tons, a waterline length of 287.5 meters, and a maximum width of 39.9 meters. This had an anticipated speed of 30.5 knots with a cruising range of 8,000 miles at 16 knots.
Optical and Angular Defects Despite those ambitious plans, the construction of the A-150 faced several setbacks. Military trials at Kure Naval Arsenal trialed a 510mm gun in 1941, but the outbreak of the Pacific War derailed subsequent modifications. When the Pacific War broke out, the Installation of a breech only fitted to one gun, with the breech itself. The other gun was only partly constructed. Overall completion of the first turret was completed at about 40 percent, with the second turret at a 20 percent complete stage when the Pacific war broke out.
The IJN forwarded plans for these ships several times under the replacement programs of the Fifth and Sixth Naval Armaments Supplement Programs. However, while the fleet had requested three battleships under both the Fifth and Sixth Programs, by early 1941 it had succeeded in getting only one authorized as an A-140 project. Those ships that were left were to be armed with the more powerful 510mm guns.
Super battleships stopped being a consideration for the future since their very large size deviated from the necessities of modern naval warfare, where aircraft carriers are a must. The defeat in the Battle of Midway in 1942 cemented the need for aircraft carriers and their fleet support ships, and Super Yamato was finally shelved for good. The prototype guns of 510mm were later melted to scrap, and design plans for the ship were destroyed.
The Super Yamato-class battleship would have been the most powerful in history, had it been completed. However, the tragedy of war and the evolution of naval strategy meant that the giant floating fortress was never able to make it out into the real world. Such a class stands as an example indicative of Japan’s insatiable ambition in matters of the navy and reminders of the continuous evolutions both in military technology and methodologies.