President Barack Obama delivers remarks at a ceremony honoring Army Gen. Martin E. Dempsey, 18th chairman of the Joint Chiefs of Staff, on Joint Base Myer-Henderson Hall, Arlington, Va., Sept. 25, 2015. The Chairman of the Joint Chiefs of Staff is the senior ranking member of the Armed Forces and principal military adviser to the President, Defense Secretary, and National Security Council Staff. DoD photo by Navy Petty Officer 2nd Class Dominique A. Pineiro