Why US exercises focused on Japan

How did the United States prioritize superiority over Japan while treating Britain differently in interwar planning?

Britain served as the demanding theoretical benchmark, but exercises and practical planning emphasized Japan as the plausible opponent; dense Anglo-American ties made an actual war far less likely.

Britain's large navy supplied a demanding opponent for theoretical wargaming, while Japan was the more plausible enemy for practical fleet exercises. Superiority over Japan therefore mattered more to US planning than parity with Britain. Hypothetical coalitions also appeared in fleet problems, including combinations involving France and Italy. Anglo-American war was considered unlikely because commercial, financial, and family connections gave disputes many routes to settlement. Intermarriage among influential families could create political resistance on both sides when governments tried to use pressure against one another. This interpretation concerns the early twentieth century and interwar period.