"An Act to Promote the Defense of the United States," informally known as the "Lend-Lease Act," is a law (or Act) written, believe it or not, with the intent to promote the safety (or Defense) of the U.S. by lending (in reality pretty much giving) arms and war supplies to whichever nation the President decided needed them, in exchange for the lease of military bases around the world or whatever the President thought was fair (really).

The "Lend-Lease Act" is easier to remember and more to the point, as the lending and leasing was how the defense of the United States was to be "promoted."