From M16 rifles to Huey helicopters, the Vietnam War launched weapons that went on to become legendary. This is the untold story of one such weapon built not by the Pentagon, but by teenage soldiers trying to keep themselves alive: the gun truck. Through interviews and home movies, meet the U.S. Army's unsung heroes: the self-made, five-ton, moving monsters that defended convoys from enemy attack and went on to influence today's combat tactics.