Two days after the start of World War II in Europe, President Roosevelt ordered the Navy to organize a neutrality patrol to report and track any belligerent air, surface, or underwater forces approaching the United States or the West Indies.
With the fall of France in June 1940, Germany gained valuable U-boat bases to press the attack against British lifelines, and possibilities were raised of German occupation of French territories in the Western Hemisphere. Assigned additional responsibilities in defense of this hemisphere, the U.S. Navy began the escort of convoys to Iceland. U-boat attacks on the convoys brought American destroyers into combat.
The Battle of the Atlantic, on which the survival of Great Britain and the projection of the United States' power overseas depended, continued until VE-Day, almost four years later.