Takao class and the intelligence gap over displacement

How did foreign navies estimate the real size of secretive Japanese cruisers such as the Takao class?

American estimates were low, while British officers used China Station photographs of Japanese and known British hulls to support better engineering estimates.

American intelligence placed the Takao class just below the nominal 10,000-ton treaty ceiling. Its actual as-built standard displacement was roughly 2,000 tons higher, with a full-load figure approaching 15,000 tons. British estimates tended to be closer because officers on the China Station photographed Japanese ships beside British hulls of known dimensions. Naval engineers could scale the images and produce more realistic calculations without relying only on human reports. The case connects treaty evasion to the practical craft of peacetime naval intelligence.