Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, arrives to place a wreath at the Tomb of the Unknown Soldier at Arlington National Cemetery in Arlington, Va., Sept. 25, 2015. Dempsey laid the wreath to honor unknown service members as he prepared to retire after 41 years of service. Maj. Gen. Bradley A. Becker, commanding general of the Military District of Washington, hosted the ceremony.