Army 1st Lt. Virgil Walker, right, looks on while Army Staff Sgt. David Rivera places an American flag in front of a headstone during "Flags In" at Arlington National Cemetery in Arlington, Va., May 25, 2017. Walker is a transportation platoon leader, and Rivera is a squad leader assigned to the 3rd U.S. Infantry Regiment, known as "The Old Guard.” DoD photo by Sebastian J. Sciotti Jr.