Lend-Lease, an Act of the US Congress passed March 1941, providing for the transfer of American war materials to Britain and its allies in return for theoretical deferred payment. Canada's involvement in WORLD WAR II had caused serious deterioration in the BALANCE OF PAYMENTS vis-à-vis the US, and the Lend-Lease Act threatened to divert all British war orders from Canada to the US.

To avert a crisis, on April 20 Prime Minister Mackenzie King and President F.D. Roosevelt issued the Hyde Park Declaration, named for the latter's Hyde Park estate, where they met, providing for American war purchases in Canada. American-produced components of war materiel manufactured in Canada for Britain were to be included in the Lend-Lease scheme, an arrangement which alleviated Canada's trade deficit and made it easier for Canada to fill British orders and guarantee financing for them. Lend-Lease, terminated August 1945, greatly helped the war efforts of Britain, the USSR and some other Allied powers; it benefited Canada only indirectly.