Fifty-one years ago today, April 30, 1975, the last American helicopter lifted off the Saigon embassy roof. We had won. Nixon and Kissinger’s Paris Peace Accords forced the North to recognize South Vietnam’s sovereignty. America promised air power and supplies if they violated it. The ARVN was finally ready to defend itself. Then Watergate. Democrats won huge majorities in 1974. They slashed aid by over 75%, banned any U.S. response to Soviet rearmament of the North, and watched as the Communists violated every agreement. No bullets. No gas. No tires for their Jeeps. South Vietnam collapsed—not from lack of courage,...