Clark McAdams Clifford was an American lawyer who served as an important political adviser to Democratic presidents Harry S. Truman, John F. Kennedy, Lyndon B. Johnson, and Jimmy Carter. His official government positions were White House Counsel (1946–1950), Chairman of the President's Intelligence Advisory Board (1963–1968), and Secretary of Defense (1968–1969); Clifford was also influential in his role as an unofficial, informal presidential adviser in various issues. A successful Washington, D.C., lawyer, he was known for his elite clientele, charming manners, and impeccable suits.

The United States secretary of defense (SecDef) is the head of the United States Department of Defense, the executive department of the U.S. Armed Forces, and is a high-ranking member of the federal cabinet. The secretary of defense's position of command and authority over the military is second only to that of the president of the United States, who is the commander-in-chief. This position corresponds to what is generally known as a defense minister in many other countries. The secretary of defense is appointed by the president with the advice and consent of the Senate, and is by custom a member of the Cabinet and by law a member of the National Security Council.