The hum of aircraft overhead signaled to American fighters on the ground that another herbicide spraying was on its way. But that wasn’t the only place where troops in the Vietnam War were exposed to Agent Orange, a chemical defoliant the U.S. military used to kill vegetation and give the enemy fewer places to hide. To boost morale, soldiers in the field were treated to steaks, but grills weren’t available, “so they made some makeshift grills out of Agent Orange barrels,” Army veteran Larry Martin said.