If Japan had revealed the Yamato class

What would have happened if Japan announced the Yamato class to the other major naval powers when the ships were laid down?

Disclosure around the 1937 laying-down dates could accelerate Montana planning and a British 16-inch Lion response, with possible changes to the least advanced King George V hulls; the panel leaves political decisions and industrial tradeoffs conditional.

The counterfactual depends on when Japan reveals its 18-inch battleships. Disclosure at launch in 1940 would leave much less time to reshape construction than an announcement around the 1937 laying-down dates, particularly if Japan advertised several ships. The panel considers Montana or larger American variants and a British stretched Lion with twelve 16-inch guns. Earlier suggestions include changing the King George V armament to nine 15-inch or nine 16-inch guns, but the later discussion acknowledges that all five hulls were already laid down by November 1937. Howe and Anson were still early enough in construction to enter the redesign speculation. One contributor also cautions that Churchill could still pause battleship construction. Carrier priority, cruiser capacity, and Vanguard remain competing constraints on the hypothetical response.