By the summer of 1940, the American government had reached the conclusion that the war in Europe had the potential to involve the United States. Consequently, President Franklin D. Roosevelt met with the Canadian prime minister, William Lyon Mackenzie King, in August to discuss the defence of North America.
As a result of their discussions, the two leaders concluded the Ogdensburg Agreement. Signed on 17 August 1940, the agreement called for the establishment of a joint American-Canadian board to coordinate the defence of North America. The meetings at Ogdensburg also led to negotiations between the British and American governments that would be extremely helpful to the Allied war effort. Eventually, the American navy agreed to send 50 American destroyers to the Royal Navy and Royal Canadian Navy in exchange for leases to several British bases in North America. This arrangement was finalized in the Destroyers-for-Bases Agreement of 5 September 1940.