It was 1968 and Robert Hartley was on his first combat mission in Vietnam as copilot of a helicopter gunship. As he and his platoon leader flew over the A Shau Valley, a Chinook helicopter engulfed in flames suddenly came into view. Hartley noticed tiny black smoking objects exiting the tail ramp of the aircraft. Seconds later, he realized those objects were men escaping the flames and plunging to their deaths. It was in that moment that he silently...