Yamato's size and the case for big-gun deterrence

Were the Yamato-class battleships intended to look weak so an enemy would send an inadequate force into an ambush?

No. Their immense size could not plausibly conceal their power, and the class belongs to Japan's long-running big-ships, big-guns deterrent policy.

Carrier priorities in 1942 do not explain why battleships were ordered in 1938-39. Yamato's roughly 72,000-ton full-load displacement made the ship visibly unlike a treaty battleship, while British and American intelligence already understood that Japan was building exceptionally large ships. A British gun-caliber estimate is recalled as about 17.5 inches, close enough to warn of very heavy armament. A hypothetical ship of roughly 36,000-38,000 tons standard, with 40,000 as an upper limit and six 18-inch guns in two forward triple turrets, would be easier to disguise as a weaker opponent. That smaller design is an illustrative alternative, not an identified Japanese construction proposal. Yamato's much larger nine-gun design fits taikan kyohō shugi, the big-ships, big-guns policy behind Japanese capital-ship procurement and deterrence.