During the early years of World War II, the United States maintained formal relations with Vichy France. Under the Monroe Doctrine, the US was strongly opposed to any change in control of the islands by force. However, Canada (perhaps due to pressure from Winston Churchill) expressed worries about Vichy forces near Canada. De Gaulle realized that Canada might want to capture Saint Pierre and Miquelon (thereby eliminating French territory so close to Quebec), so he secretly planned its seizure by Free France. On Christmas Eve 1941, Free French forces (three corvettes and the submarine "Surcouf", led by Rear-Admiral Émile Muselier) "invaded" the islands. The Vichy officials immediately surrendered.