Caspar Willard Weinberger was an American politician and businessman. As a Republican, he served in a variety of state and federal positions for three decades, most notably as Secretary of Defense under President Ronald Reagan from January 1981 to November 1987. He was indicted on charges of lying to Congress and obstructing government investigations as part of the Iran–Contra investigation, but was pardoned by President George H. W. Bush before facing trial.

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.