18th Chairman of the Joint Chiefs of Staff Army Gen. Martin E. Dempsey speaks with ABC news' Martha Raddatz during an interview at the Pentagon, Sept. 2, 2015. During the wide-ranging interview, Dempsey reflected on his life in the military, his work with President Barack Obama and the challenges his successor, Marine Corps Gen. Joseph F. Dunford, will face. DoD photo by U.S. Army Staff Sgt. Sean K. Harp