Complex sentence: One achievement was that they warranted in shifting some of its cruises to European waters, using the ports of their ally, France, as a base of operation; although it did not totally hinder nor prevent the Royal Navy from going anywhere in American waters.
Split into simpler sentences: One achievement was that they warranted in shifting some of its cruises to European waters, using the ports of their ally, France, as a base of operation. Although it did not totally hinder nor prevent the Royal Navy from going anywhere in American waters.