Colin Powell served in a body of the United States Department of Defense.
The Chairman of the Joint Chiefs of Staff ( CJCS ) is , by U.S. law , the highest-ranking and senior-most military officer in the United States Armed Forces and is the principal military advisor to the President , the National Security Council , the Homeland Security Council , and the Secretary of Defense . The Chairman convenes the meetings and coordinates the efforts of the Joint Chiefs of Staff ( JCS ) , an advisory body within the Department of Defense comprising the Chairman , the Vice Chairman of the Joint Chiefs of Staff , the Chief of Staff of the Army , the Chief of Naval Operations , the Chief of Staff of the Air Force , the Commandant of the Marine Corps , and the Chief of the National Guard Bureau . Colin Powell . During his military career , Powell also served as National Security Advisor ( 1987 -- 1989 ) , as Commander of the U.S. Army Forces Command ( 1989 ) and as Chairman of the Joint Chiefs of Staff ( 1989 -- 1993 ) , holding the latter position during the Persian Gulf War . The Joint Chiefs of Staff ( JCS ) is a body of senior uniformed leaders in the United States Department of Defense who advise the President of the United States , the Secretary of Defense , the Homeland Security Council and the National Security Council on military matters .