U.S. Department of Defense

Executive Order 14347 of 2025 recalls that on August 7, 1789, President George WashingtonGeorge WashingtonGeorge Washington (1732–1799) was the first president of the United States, serving from 1789 to 1797. Earlier he commanded the Continental Army in the American Revolutionary War and presided over the Constitutional Convention of 1787.Open the full entry signed a bill establishing the Department of War to oversee the operation and maintenance of military and naval affairs, and states that the Department of War, together with the later Department of the Navy, won the War of 1812, World War I and World War II.⁠[1]

On July 26, 1947, President Harry S. TrumanHarry S. TrumanHarry S. Truman (1884–1972) was an American politician who served as a U.S. senator from Missouri and as vice president in 1945, succeeding Franklin D. Roosevelt on his death that year and serving as the 33rd president of the United States from 1945 to 1953, a period spanning the end of World War II and the early Cold War.Open the full entry approved the compromise version of the National Security Act of 1947, which became Public Law 253 of the 80th Congress. The act reorganized the U.S. foreign policy and military establishments: the War Department and the Navy Department were merged under a Secretary of Defense, a new Department of the Air Force was created, each of the three branches kept its own service secretary, and the National Security Council and the Central Intelligence AgencyCentral Intelligence AgencyThe Central Intelligence Agency (CIA) is an independent U.S. intelligence agency established under the National Security Act of 1947 to provide national security intelligence to senior U.S. policymakers. It is headquartered in Langley, Virginia.Open the full entry were established.⁠[2][3]

James V. Forrestal, Secretary of the Navy since May 19, 1944, was sworn in on September 17, 1947, as the first Secretary of Defense, heading the National Military Establishment created under the act. The act gave the secretary only “general” responsibility for the “direction, authority, and control” of the establishment, and the heads of the military departments were “virtually autonomous,” which limited his authority. Forrestal resigned on March 28, 1949.⁠[4]

The amendments to the National Security Act of August 10, 1949 (Public Law 216, 81st Congress) replaced the National Military Establishment with the Department of Defense, an executive department, and made the Army, Navy and Air Force military departments within it; they removed the word “general” and strengthened the Secretary of Defense’s control over the services and their secretaries.⁠[4][3][2]

Following a presidential message from Dwight D. EisenhowerDwight D. EisenhowerDwight D. Eisenhower (1890–1969) was an American army general and politician who served as supreme commander of Allied forces in western Europe during World War II and as the 34th president of the United States, a Republican, from 1953 to 1961.Open the full entry to Congress in April 1953 on reorganizing the Department, Reorganization Plan No. 6 of 1953 took effect on June 30, 1953.⁠[2]

The Defense Reorganization Act of 1958 became law on August 6, 1958.⁠[2]

Robert McNamaraRobert McNamaraRobert McNamara (Robert Strange McNamara, 1916–2009) was an American business executive and government official who was president of the Ford Motor Company, served as U.S. secretary of defense under John F. Kennedy and Lyndon B. Johnson from 1961 to 1968, and was president of the World Bank from 1968 to 1981.Open the full entry (Robert S. McNamara) served as the eighth Secretary of Defense from January 21, 1961, to February 29, 1968.⁠[5]

The department’s Historical Office lists the National Security Act of 1947, its 1949 amendment, the Goldwater–Nichols Act of 1986 and the 1993 Bottom-Up Review under Secretary of Defense Les Aspin as the department’s major reforms.⁠[6]

Pete HegsethPete HegsethPete Hegseth (born 1980) is an American politician, author and former television host who has been the 29th U.S. secretary of defense since 2025, also styled Secretary of War since September 2025.Open the full entry (Peter B. Hegseth) was sworn in as the 29th Secretary of Defense on January 25, 2025.⁠[7]

The Historical Office’s biography of Hegseth states that on September 5, 2025, President Donald Trump signed an executive order authorizing the Secretary of Defense, the Department of Defense and subordinate officials to use the secondary names “Secretary of War” and “Department of War.”⁠[7]

Executive Order 14347 allows the secondary names in official correspondence, public communications, ceremonial contexts and non-statutory executive branch documents, while statutory references to the Department of Defense remain controlling until changed by law. It directed the Secretary to recommend, within 60 days, the legislative and executive actions needed to permanently change the name of the Department of Defense to the Department of War.⁠[1]

As of November 2026, the Historical Office lists Hegseth as the serving Secretary of Defense. The department’s website, which uses the name “Department of War,” lists a national defense budget of $841.4 billion, 3.4 million service members and civilians, 4,800 sites in more than 160 countries and 11 combatant commands.⁠[7][8]

The Secretaries of Defense from 1947 to 2019 were James V. Forrestal, Louis A. Johnson (1949–1950), George C. MarshallGeorge C. MarshallGeorge C. Marshall (1880–1959) was a five-star U.S. Army general and statesman. He was Army chief of staff during World War II and later served as secretary of state and secretary of defense, and he received the 1953 Nobel Peace Prize for proposing and supervising the plan for Europe’s economic recovery, the Marshall Plan.Open the full entry (September 21, 1950–September 12, 1951), Robert A. Lovett (1951–1953), Charles E. Wilson (1953–1957), Neil H. McElroy (1957–1959), Thomas S. Gates, Jr. (1959–1961), Robert S. McNamara, Clark M. Clifford (1968–1969), Melvin R. Laird (1969–1973), Elliot L. Richardson (1973), James R. Schlesinger (1973–1975), Donald H. Rumsfeld (1975–1977 and again 2001–2006), Harold Brown (1977–1981), Caspar W. Weinberger (1981–1987), Frank C. Carlucci (1987–1989), Richard B. Cheney (1989–1993), Leslie Aspin (1993–1994), William J. PerryWilliam J. PerryWilliam J. Perry is an American engineer, businessman and former secretary of defense whose tenure included acquisition reform and nuclear threat reduction.Open the full entry (1994–1997), William S. Cohen (1997–2001), Robert M. Gates (2006–2011), Leon E. Panetta (2011–2013), Charles T. Hagel (2013–2015), Ashton B. Carter (2015–2017) and James N. MattisJames MattisJames Mattis is a retired U.S. Marine Corps general and former commander of U.S. Central Command. He served as U.S. secretary of defense from January 2017 through December 2018. A former Theranos director and personal investor, he later testified at Elizabeth Holmes’s criminal trial.Open the full entry (2017–2018); Patrick M. Shanahan became Acting Secretary of Defense on January 1, 2019.⁠[5]

They were followed by Mark T. Esper, the 27th Secretary, from July 23, 2019, to November 9, 2020, and Lloyd J. Austin III, the 28th Secretary, from January 22, 2021, to January 20, 2025.⁠[9][10]

U.S. Department of Defense: Official website: https://www.war.gov/ (opens in a new window).⁠[8]