The Lend-Lease Act, officially known as the "An Act to Promote the Defense of the United States," was passed by the United States Congress in March 1941. It allowed the United States to provide military aid, including weapons and other supplies, to Britain and other Allied nations during World War II without requiring immediate cash payment upfront. Instead, the recipient countries were allowed to pay back the cost of the aid in kind or with other goods and services after the war.