Since the 19th century, many if not all presidents were assisted by a central figure or "gatekeeper", sometimes described as the President's Private Secretary, sometimes with no official title at all. Eisenhower formalized this role, introducing the office of White House Chief of Staff – an idea he borrowed from the United States Army. Every president after Lyndon Johnson has also appointed staff to this position. Initially, Gerald Ford and Jimmy Carter tried to operate without a chief of staff, but each eventually appointed one.