In September 2025, President Donald Trump signed an executive order that officially renamed the Department of Defense to the ‘Department of War.’ This change, which aims to return to the original title established during the Revolutionary War, reflects Trump’s emphasis on military strength and preparedness as vital to U.S. national security. The order states, “The name ‘Department of War,’ more than the current ‘Department of Defense,’ ensures peace through strength as it demonstrates our ability and willingness to fight and win wars on behalf of our nation at a moment’s notice, not just to defend.”
The Department of Defense underwent its initial rebranding following World War II, when President Harry Truman sought to reshape the U.S. military establishment in response to the global political landscape. In the wake of the war, which marked the most devastating armed conflict in history, Truman emphasized the need for a comprehensive national security program. In a statement made in autumn 1945, he asserted the importance of timely preparations for long-range security, stating, “I pointed out the necessity of making timely preparation for the nation’s long-range security now – while we are still mindful of what it has cost us in this war to be unprepared.”
September 18, 1947, marked a pivotal moment in U.S. military history when Truman signed legislation merging the Army, Navy, and Air Force into a single entity under the newly established Department of Defense. This significant shift aimed to enhance efficiency, coordination, and unity of command while reinforcing civilian control over the military. Truman’s proposal included unifying the War and Navy Departments into the Department of National Defense, a vital step toward strengthening national security.
The National Security Act of 1947 established the National Military Establishment (NME), which separated the Air Force from the Army and created the role of Secretary of Defense. This cabinet position was designated for a civilian or a military retiree who had been out of service for at least ten years, a requirement that was later amended to seven years. The act also established the Joint Chiefs of Staff, comprising high-ranking military officers, along with the Central Intelligence Agency and the National Security Council.
Two years later, the NME was renamed the Department of Defense. This rebranding was driven by the challenges encountered during World War II and the emerging threat of the Soviet Union during the Cold War. The change from War Department to the Department of Defense was not merely a semantic decision; it aimed to distinguish the new structure from the previous military alignment that had persisted since the 18th century. Interestingly, some sources suggest that the acronym NME was perceived negatively, as it sounded too much like “enemy.”
The original War Department was established on August 7, 1789, during the first session of Congress under President George Washington. Its purpose was to replace the Board of War and Ordnance, which had been created during the American Revolution in 1776. Initially referred to as the War Office, the War Department also encompassed the fledgling U.S. Navy, which became a separate cabinet position in 1798, including the command of the U.S. Marine Corps.
The National Security Act of 1947 effectively separated the Department of the Army from the Department of War and established the Department of the Air Force as a distinct military branch. The amended act, signed by Truman on August 10, 1949, brought the secretaries of the Army, Navy, and Air Force under the Secretary of Defense and created the position of chairman of the Joint Chiefs of Staff.
Truman characterized these revisions as a “unification… increased efficiency and economy and greater coordination of our military forces.” While the comprehensive restructuring aimed to enhance inter-service cooperation, it also sparked intense rivalry among the branches, particularly between the Air Force and Navy regarding the management of the U.S. nuclear arsenal. The effectiveness of this realignment continues to be debated as it shapes military operations to this day.
As the Department of War re-emerges in official nomenclature, the implications of this shift will likely reverberate throughout military policy and international relations, reflecting a renewed focus on the United States’ military capabilities.
