Visible Japanese hulls and an official announcement in 1939 would make the existing British and American rearmament programs politically inadequate. Newspaper comparisons of enormous ships and guns could block deployment of older US standards to Hawaii, accelerate upgrades, and compel both navies to enlarge their new capital-ship plans regardless of the Yamatos' eventual combat effectiveness.
Notable Point · 3:35:57-3:38:03
What public knowledge of Yamato could trigger
Announcing the Yamato class during construction could force Britain and the United States into larger battleship and modernization programs even before the ships fight.