[5][6][7] 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.

[9] To ensure civilian control of the military, U.S. law provides that the secretary of defense cannot have served as an active-duty commissioned officer in the military in the preceding seven years except for generals and admirals, who cannot have served on active duty within the previous ten years.

Congress can legislatively waive this restriction[10] and has done so three times, for George C. Marshall, James N. Mattis, and Lloyd J. Austin III.

[11] Because the secretary of defense is vested with legal powers that exceed those of any commissioned officer, and is second only to the president in the military hierarchy, its incumbent has sometimes unofficially been referred to as "deputy commander-in-chief".

[20] The current secretary of defense is Pete Hegseth, who was nominated by President-elect Donald Trump and was confirmed by the Senate on January 25, 2025.

Based on the experiences of World War II, proposals were soon made on how to more effectively manage the large combined military establishment.

The Army generally favored centralization while the Navy had institutional preferences for decentralization and the status quo.

The last major revision of the statutory framework concerning the position was done in the Goldwater–Nichols Department of Defense Reorganization Act of 1986.

[22][23] The secretary of defense, appointed by the president with the advice and consent of the Senate, is by federal law (10 U.S.C.

The latest version, signed by former secretary of defense Robert Gates in December 2010, is the first major re-write since 1987.

While the approval authority for DSSM, DMSM, JSCM, JSAM and JMUA is delegated to inferior DoD officials: the DDSM can be awarded only by the secretary of defense.

The shortest-serving secretary of defense is Elliot Richardson, who served 114 days and then was appointed U.S. attorney general amid the resignations of the Watergate Scandal.

It is hereby expressed as the sense of the Congress that after General Marshall leaves the office of Secretary of Defense, no additional appointments of military men to that office shall be approved.Defenselink bio Archived November 18, 2008, at the Wayback Machine, Retrieved February 8, 2010; and Marshall Foundation bio Archived September 27, 2011, at the Wayback Machine, Retrieved February 8, 2010.