Britain and the United States both maintained plans for a possible war against the other. Each was the other great naval and military power whose capabilities could not be ignored by a professional staff. A contingency plan prevented commanders from being wholly unprepared if politics changed unexpectedly. Such planning reflected routine strategic prudence, almost a form of professional courtesy, rather than an intention to fight.
Notable Point · 1:39:59-1:40:28
Why Britain and America kept contingency plans against each other
Planning for a war with the other major naval power was professional preparedness, not proof that either government intended to start one.