What Anglo-American war plans did - and did not - mean

British and American interwar contingency plans do not by themselves prove that either government expected war. Each navy used the other first-rate power as the hardest planning and exercise problem, because preparing against a lesser opponent would test less of the staff and fleet. An informal diplomatic anecdote in which Halifax's shared importance was discussed almost humorously illustrates how closely the two states communicated while their staffs examined conflict. A real war would have been mutually ruinous: Britain could threaten both American coasts, while U.S. concentration would expose long logistics lines and dispersion would dilute the fleet's central strength. Senior review comments also focused more on planning method in the Anglo-American case, whereas plans involving Japan, Italy, or France drew greater attention to operational content, so the documents must be interpreted in their institutional context.