Passed on March 11, 1941, the Lend-Lease Act set up a system that would allow the United States to lend or lease war supplies to any nation deemed "vital to the defense of the United States."

In July 1940, after Britain had sustained the loss of 11 destroyers to the German Navy over a 10-day period, newly elected British Prime Minister Winston Churchill requested help from President Roosevelt. Roosevelt responded by exchanging 50 destroyers for 99-year leases on British bases in the Caribbean and Newfoundland. As a result, a major foreign policy debate erupted over whether the United States should aid Great Britain or maintain strict neutrality.

In the 1940 Presidential election campaign, Roosevelt promised to keep America out of the war. He stated, "I have said this before, but I shall say it again and again and again; your boys are not going to be sent into any foreign wars." Nevertheless, FDR wanted to support Britain and believed the United States should serve as a "great arsenal of democracy." Churchill pleaded, "Give us the tools and we'll finish the job." In January 1941, following up on his campaign pledge and the prime minister's appeal for arms, Roosevelt proposed to Congress a new military aid bill.

The plan proposed by FDR was to "lend-lease or otherwise dispose of arms" and other supplies needed by any country whose security was vital to the defense of the United States. In support of the bill, Secretary of War Henry L. Stimson told the Senate Foreign Relations Committee during the debate over lend-lease, "We are buying . . . not lending. We are buying our own security while we prepare. By our delay during the past six years, while Germany was preparing, we find ourselves unprepared and unarmed, facing a thoroughly prepared and armed potential enemy." Following two months of debate, Congress passed the Lend-Lease Act, meeting Great Britain’s deep need for supplies and allowing the United States to prepare for war while remaining officially neutral.