 The main defence priority at the time of Confederation was deterring a possible attack by the United States, with which tensions were elevated on account of perceived British and Canadian sympathy for the Confederate cause during the American Civil War.However, the vast Canada–United States border limited the level of attention that could be directed to the maritime implications of any hypothetical war with the U.S.In any event, the United States Navy was neglected in the decades following the American Civil War and relations between London and Washington improved after the Treaty of Washington was signed in 1871.