However, some nations, such as the United States, resisted British coercion. The US believed strongly in freedom of the seas and, on several occasions, refused to allow the Royal Navy right of search. Knowing that many slavers would fly false US flags to avoid being boarded, some slavers were even registered in southern US states. This caused several diplomatic incidents as frustrated officers would often board ships with US flags, directly contravening their orders, to capture slavers. In the US Congress there was fierce opposition to this, with John Forsyth stating in 1841 that “the persistence” of British cruisers was “unwarranted,” “destructive to private interests” and “inevitably destroy the harmony of the two countries.” In 1842 there was a thaw in diplomatic relations and the US allowed visitation to US vessels, but only if a US officer was also present.