Colin Powell worked in a body of the United States Department of Defense.
His last assignment , from October 1 , 1989 to September 30 , 1993 , was as the 12th Chairman of the Joint Chiefs of Staff , the highest military position in the Department of Defense.
The Chairman convenes the meetings and coordinates the efforts of the Joint Chiefs of Staff -LRB- JCS -RRB- , 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.
