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.

I think it's a much more appropriate name, in light of where the world is right now, Trump said in the Oval Office on Friday, adding that it sends a message of victory.

The order states that Secretary of Defense Pete Hegseth will be known as the Secretary of War. It instructs him to recommend and include legislative and executive actions to move towards a permanent renaming of the department.

Speaking during the signing, Hegseth said, this name change is not just about renaming, it's about restoring, adding words matter.

We're going to go on offense, not just on defense. Maximum lethality, not tepid legality. Violent effect, not politically correct, he said. 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 rests with the US Congress. In August, Trump told reporters he was confident Congress would support the idea - if their support was needed.

Democratic Senator Andy Kim of New Jersey criticized the renaming as a childish idea, stating: Americans want to prevent wars, not tout them.

The Department of War was established by George Washington, but was rebranded following World War Two.

Trump had repeatedly floated the idea of the name change, arguing that the US has an unbelievable history of victory in both world wars under the previous name.

Trump and Hegseth have sought to refocus the department on warfighting and a warrior ethos while criticizing a perceived overemphasis on diversity and equity initiatives within the Pentagon.

The renaming marks Trump's 200th executive order since taking office, and the initiative comes amidst heightened global tensions, particularly attributed to China's recent military demonstrations.