Source: https://military.wikia.org/wiki/United_States_Secretary_of_Defense
Timestamp: 2019-04-20 18:19:23+00:00

Document:
The current Secretary of Defense is Patrick M. Shanahan, who assumed office on 1 January 2019 as Acting United States Secretary of Defence following the resignation of then secretary James Mattis.
The Army, Navy, and Marine Corps were established in 1775, in concurrence with the American Revolution. The War Department, headed by the Secretary of War, was created by Act of Congress in 1789 and was responsible for both the Army and Navy until the founding of a separate Department of the Navy in 1798.
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 resulting National Security Act of 1947 was largely a compromise between these divergent viewpoints. The Act split the War Department into the Department of the Army and the Department of the Air Force, each with their own Secretary, and created a sui generis National Military Establishment led by a Secretary of Defense. At first, each of the service secretaries maintained quasi-cabinet status. The first Secretary of Defense, James Forrestal, who in his previous capacity as Secretary of the Navy had opposed creation of the new position, found it difficult to exercise authority over them with the limited powers his office had at the time. To address this and other problems, the National Security Act was amended in 1949 to further consolidate the national defense structure in order to reduce interservice rivalry, directly subordinate the Secretaries of the Army, the Navy and the Air Force to the Secretary of Defense in the chain of command, and rename the National Military Establishment to the Department of Defense as one Executive Department. The position of the Deputy Secretary of Defense, the number two position in the department, was also created at this time.
The Secretary of War [now Secretary of Defense] is the regular constitutional organ of the President for the administration of the military establishment of the nation; and rules and orders publicly promulgated through him must be received as the acts of the executive, and as such, be binding upon all within the sphere of his legal and constitutional authority. Such regulations cannot be questioned or denied because they may be thought unwise or mistaken. .
The Secretary is one of few civilians — others are the President, the three "service secretaries" (the Secretary of the Army, Secretary of the Navy, and Secretary of the Air Force), and the Secretary of Homeland Security (when the United States Coast Guard is under the United States Department of Homeland Security and has not been transferred to the Department of the Navy under the Department of Defense) — authorized to act as convening authority in the military justice system for General Courts-Martial (10 U.S.C. § 822: article 22, UCMJ), Special Courts-Martial (10 U.S.C. § 823: article 23, UCMJ), and Summary Courts-Martial (10 U.S.C. § 824: article 24 UCMJ).
Secretary of Defense is a Level I position of the Executive Schedule, and thus earns a salary of $199,700 per year.
The longest-serving Secretary of Defense is the late Robert McNamara, who served for a total of 2,595 days. Combining his two non-sequential services as Secretary of Defense, the second longest serving is Donald Rumsfeld, who served merely ten days fewer than McNamara.
and the General Counsel of the Air Force.
↑ http://www.tioh.hqda.pentagon.mil/UniformedServices/Flags/Pos_Colors_DoD.aspx Archived 12 May 2013 at the Wayback Machine., accessed on 4 January 2012.
↑ "3 U.S. Code § 19 - Vacancy in offices of both President and Vice President; officers eligible to act". https://www.law.cornell.edu/uscode/text/3/19.
↑ 4.0 4.1 5 U.S.C. § 5312.
↑ Joint Publication 1: II-9, II-10 & II-11.
↑ http://www.americanprogress.org/issues/2006/10/rumsfeld.html, accessed on 2012-01-06.
↑ Obama bids farewell to defense secretary - politics - More politics | NBC News. MSNBC (2011-06-30). Retrieved on 2013-08-16.
↑ "Chuck Hagel - Barack Obama Administration". Office of the Secretary of Defense - Historical Office. http://history.defense.gov/Multimedia/Biographies/Article-View/Article/571277/chuck-hagel/.
↑ "Ashton B. Carter - Barack Obama Administration". Office of the Secretary of Defense - Historical Office. http://history.defense.gov/Multimedia/Biographies/Article-View/Article/571296/ashton-b-carter/.
↑ "James N. Mattis - Donald Trump Administration". Office of the Secretary of Defense - Historical Office. http://history.defense.gov/Multimedia/Biographies/Article-View/Article/1059855/james-n-mattis/.
↑ 3 U.S.C. § 19.
Department of Defense Directive 5100.1: Functions of the Department of Defense and Its Major Components. Department of Defense Directive. Washington, D.C.: U.S. Department of Defense. 2010-12-21. http://www.dtic.mil/whs/directives/corres/pdf/510001p.pdf.
Department of Defense Manual 1348.33, Volume 1: Manual of Military Decorations and Awards: General Information, Medal of Honor, and Defense/Joint Decorations and Awards. Department of Defense Manual. Washington, D.C.: U.S. Department of Defense. 2013-03-07. http://www.dtic.mil/whs/directives/corres/pdf/134833vol1.pdf.
Department of Defense Manual 1348.33, Volume 2: Manual of Military Decorations and Awards: General Information, Medal of Honor, and Defense/Joint Decorations and Awards. Department of Defense Manual. Washington, D.C.: U.S. Department of Defense. 2013-05-31. http://www.dtic.mil/whs/directives/corres/pdf/134833vol2.pdf.
Department of Defense Manual 1348.33, Volume 3: Manual of Military Decorations and Awards: General Information, Medal of Honor, and Defense/Joint Decorations and Awards. Department of Defense Manual. Washington, D.C.: U.S. Department of Defense. 2010-11-23. http://www.dtic.mil/whs/directives/corres/pdf/134833vol3.pdf.
Joint Publication 1 – Doctrine for the Armed Forces of the United States. Joint Publications. Washington, D.C.: U.S. Department of Defense. 2013-03-25. http://www.dtic.mil/doctrine/new_pubs/jp1.pdf.
Joint Publication 1-04 – Legal Support to Military Operations. Joint Publications. Washington, D.C.: U.S. Department of Defense. 2011-08-17. http://www.dtic.mil/doctrine/new_pubs/jp1_04.pdf.
Cole, Alice C.; Goldberg, Alfred; Tucker, Samuel A. et al., eds (1978). The Department of Defense: Documents on Establishment and Organization 1944-1978. Washington, D.C.: Historical Office, Office of the Secretary of Defense/U.S. Government Printing Office. http://history.defense.gov/resources/DODDocsEstandOrg1944-1978.pdf.
King, Archibald (1949/1960 reprint). Command of the Army. Military Affairs. Charlottesville, Virginia: The Judge Advocate General's School, U.S. Army. http://www.loc.gov/rr/frd/Military_Law/pdf/Command-Army_King.pdf.
Mahan, Erin R., and Jeffrey A. Larsen, eds. (2012) “Evolution of the Secretary of Defense in the Era of Massive Retaliation: Charles Wilson, Neil McElroy, and Thomas Gates, 1953–1961,” Cold War Foreign Policy Series: Special Study 3 (September 2012), vii–41.
Trask, Roger R.; Goldberg, Alfred (1997). The Department of Defense 1997-1947: Organization and Leaders. Washington, D.C.: Historical Office, Office of the Secretary of Defense/U.S. Government Printing Office. ISBN 0-16-049163-0. http://history.defense.gov/resources/DOD1947-1997OrgLeaders.pdf.
The Department of Defense Key Officials 1947-2013. Washington, D.C.: Historical Office, Office of the Secretary of Defense. 2013. http://history.defense.gov/resources/DODKeyOfficials1947-2012.pdf.
"Department of Defense Directive 5100.01 Functions of the Department of Defense and Its Major Components". Office of the Secretary Defense, Director of Administration and Management, Directorate for Organizational & Management Planning. http://odam.defense.gov/omp/Functions/Organizational_Portfolios/Evolution%20of%205100.1.html. Retrieved 13 June 2013.

References: sui generis
 § 822
 § 823
 § 824
 § 19
 § 5312
 § 19