US President Donald Trump signed an executive order on Friday that directs the Department of Defense to be known as the Department of War.
The move restores a name the agency last held in the 1940s and, according to the text of the order seen by the BBC, the aim is to project strength and resolve.
The department will initially use the new name as a secondary title while the administration seeks congressional approval to make the change permanent.
The White House is yet to say how much a rebrand would cost, but US media expect a billion-dollar price tag for the overhaul of hundreds of agencies, emblems, email addresses and uniforms.
The Department of Defense (DoD) - which oversees the US armed services - is the successor to the War Department, which was first established as a cabinet-level agency in 1789 and existed until 1947.
The executive order says: The name 'Department of War' conveys a stronger message of readiness and resolve compared to 'Department of Defense,' which emphasizes only defensive capabilities.
Trump stated, I think it's a much more appropriate name, in light of where the world is right now, adding that it sends a message of victory.
The order states that Secretary of Defense Pete Hegseth will now be known as the secretary of war, instructing him to recommend legislative and executive actions to move towards a permanent renaming of the department.
During the signing, Hegseth remarked, This name change is not just about renaming, it's about restoring. Words matter. He further stated, We're going to go on offense, not just on defense. Maximum lethality, not tepid legality. Violent effect, not politically correct. We're going to raise up warriors, not just defenders.
The Pentagon's website changed to war.gov late on Friday, along with the headline 'U.S. Department of War'.
The responsibility of creating executive departments lies with the US Congress. In August, Trump expressed confidence that Congress would support the idea.
Critics, including Democratic Senator Andy Kim of New Jersey, have dismissed the renaming as a childish idea, asserting that Americans prefer efforts to prevent wars rather than promote them.
Historically, the Department of War was established by George Washington but was rebranded following World War II. Trump has long argued that the US has an unbelievable history of victory under the prior name.
The renaming of the department marks the president's 200th executive order signed since he took office, coinciding with China's display of new military capabilities in recent parades.
