American Military History, Volume 2 by Richard W. Stewart

On the eve of France's defeat in June 1940, President Roosevelt had directed the transfer or diversion of large stocks of World War I weapons, ammunition, and aircraft to both France and Great Britain. After France fell, these munitions helped to replace Britain's losses from the evacua- tion of its expeditionary force at Dunkerque. Additional aid to Britain materialized in September, when the United States agreed to exchange fifty over-age destroyers for offshore Atlantic bases and the President an- nounced that future U.S. production of heavy bombers would be shared equally with the British. Open collaboration with Canada from August 1940 provided strong support for the Canadian war effort (Canada had followed Great Britain to war in September 1939). These foreign aid ac- tivities culminated in the Lend-Lease Act of March 1941 that swept away the pretense of American neutrality by openly avowing the intention of the United States to become an "arsenal of democracy" against aggression. Prewar foreign aid was largely a self-defense measure; its fundamental purpose was to help contain the military might of the Axis powers until the United States could complete its own protective mobilization.

Thus by early 1941 the focus of American policy had shifted from hemispheric defense to limited participation in the war. Indeed, by then it appeared to Army and Navy leaders and to President Roosevelt that the United States might be drawn into full participation in the not-too-distant future. Assuming the probability of simultaneous operations in the Pacific and the Atlantic, they agreed that Germany was the greater menace and that if the United States did enter the war it ought to con- centrate first on the defeat of Germany. This principle was established as shared policy in staff conversations between American and British military representatives in Washington ending on March 29.