ARLINGTON, VA - MAY 21:  Members of the 3rd U.S. Infantry Regiment place American flags at the graves of U.S. soldiers buried at Arlington National Cemetery, in preparation for Memorial Day May 21, 2015 in Arlington, Virginia. 'Flags-In' has become an annual ceremony since the 3rd U.S. Infantry Regiment (The Old Guard) was designated to be an Army's official ceremonial unit in 1948  (Photo by Win McNamee/Getty Images)