President Trump’s bid to knock four letters off the “Department of Defense” in a rebrand to the “Department of War” could cost upwards of $100 million, the Congressional Budget Office (CBO) has estimated.

On September 5, the president signed an executive order to restore the George Washington-era names of the Department of War and the Office of the Secretary of War as secondary titles for the Department of Defense and the Office of the Secretary of Defense.

Within that order was a stipulation that the Secretary of War would later submit a presidential application to permanently change the name of the department.

However, rebranding the nation’s biggest employer is no small task. The Pentagon oversees 1.32 million people in active duty and 750,000 civilian personnel.

According to the CBO, which responded to a request for information from senators Jeff Merkley and Chuck Schumer, the shift would cost about $10 million for a “modest implementation” of the change, primarily within the department itself. This sum could be absorbed as an opportunity cost, the CBO added, paid out of existing budgets.