The plan was devised by an American merchant Thomas Cumming who had previously visited West Africa, and extensively considered the possibilities for a British attack. The plan was built around Britain's growing dominance on the Oceans which had dramatically reduced French sea power. A British naval force under Captain Henry Marsh would sail from England and head for the coast of West Africa, where it would land an amphibious force at the Senegal River. They would then capture the French fort at Saint-Louis. Cumming planned to raise support from local African forces, who would rendezvous with the British and attack the French.