Monster Battleship That Never Was

At the height of World War II, Japan quietly drew up plans for a 91,000‑ton battleship with 20‑inch guns so huge its own industry probably could never have built it.

Story Snapshot

Japan’s navy finished paper designs for the A-150 “Super Yamato” by early 1941, aiming for six 20‑inch guns.
Displacement studies pushed the ship toward roughly 85,000–91,000 tons, far beyond practical limits.
No hull was ever laid down; resources shifted to carriers and smaller warships as the Pacific war turned against Japan.
Most original plans were destroyed, leaving historians to piece the story together from scattered secondary sources.

Japan’s “Super Yamato” and the race to build bigger guns

Japanese naval planners started work around 1938–1939 on a battleship that would outclass the already massive Yamato class. The new design, called A‑150 or “Super Yamato,” was meant to carry six 51‑centimeter, or about 20‑inch, main guns in three twin turrets, the largest guns ever planned for a frontline warship. Designers also wanted heavy armor and many smaller guns for defense. On paper, this ship would have been the peak of traditional battleship power, built to outrange and outgun any American or British rival.

Early versions of the plan were even more extreme, with proposals for eight or nine 20‑inch guns and speeds near 30 knots, which pushed displacement toward or above 100,000 tons. As engineers ran the numbers, they had to scale back those dreams to something closer to 27 knots, similar to Yamato, while still adding more armor to survive hits from its own giant shells. Even in this toned‑down form, the baseline design was calculated at about 85,000 tons standard displacement, with later estimates and tests reaching around 91,000 metric tons.

Why the “Super Yamato” never left the drawing board

By early 1941, most design work on the A‑150 was complete, and planners even penciled in ship numbers and a timetable, with a keel planned for 1942 at Yokosuka Naval Shipyard. But turning drawings into steel raised hard questions. Japan’s gun industry still had to prove it could build reliable 20‑inch guns, and its steel industry struggled to make and heat‑treat armor plates thick enough for the huge turrets and belt protection the design required. The navy also realized new dry docks and port facilities would be needed, adding more cost and strain to an already stressed wartime economy.

As the Pacific war unfolded, those practical limits became impossible to ignore. Tests and calculations showed that a 91,000‑ton battleship would be “too large and too expensive” for Japan to build and support. After 1941, Japan shifted shipbuilding resources toward aircraft carriers and cruisers, which offered more flexible power for a war now defined by air combat. The A‑150 was never laid down, and the Yamato class, already huge and costly, remained the peak of Japan’s battleship program. For all its ambition, the “Super Yamato” stayed a paper giant.

Lost blueprints, mixed numbers, and the problem of “paper ships”

Much of what we know about A‑150 comes from scattered postwar accounts, naval studies, and hobby forums, not from full original Japanese blueprints. Near the end of the war, Japanese officials destroyed many plans for fear they might fall into enemy hands, including the completed A‑150 designs from early 1941. That destruction protects secrets but also leaves today’s researchers with gaps. For example, no detailed armor scheme survives, so experts must estimate protection levels from a few turret plate thickness figures and general design goals.

Because of those gaps, key numbers like displacement are debated. Some sources suggest about 64,000 tons standard, others around 72,000 tons, while design studies cite 85,000 tons and tests near 91,000 metric tons. Model kits and online art labeled “Super Yamato” often mix facts with guesswork, and even fans admit the basis for many visual reconstructions is “anyone’s guess.” This makes A‑150 a classic World War II “paper ship,” like German or American never‑built mega battleships, where grand plans met hard limits in industry, strategy, and cost.

What this forgotten giant says about power and limits

The A‑150 story shows how far great powers will go, on paper, to chase military dominance, even when home industry cannot keep up. Japanese planners dreamed of a ship that could outgun any rival, but the steel mills, shipyards, and fuel supplies that made real ships possible had clear limits. That tension between huge promises and real capacity feels familiar today, when governments of all stripes announce big projects while letting basics like infrastructure, household costs, and fair opportunity slide. People on the left and right both see leaders who chase prestige but ignore everyday needs.

These “too big to build” war plans also echo a deeper worry many Americans now share about the modern state. During World War II, Japan burned resources on designs it would never launch, while regular citizens faced shortages and, eventually, ruin. Today, many feel our own leaders pour billions into favored programs and global games while the middle class sinks and trust breaks down. The fate of the “Super Yamato” is a reminder that when elites chase grand symbols of power instead of practical strength and fairness, the country they lead can lose far more than a battleship on paper.