President Donald Trump said on Monday he had “terminated” Defense Secretary Mark Esper.
“Mark Esper has been terminated,” Trump wrote in a tweet, adding that Miller would be acting secretary “effective immediately.”
Trump had split with Esper over a range of issues.
U.S. defense officials said White House Chief of Staff Mark Meadows called Esper minutes ahead of time to alert him that Trump would be firing him through Twitter.
Trump said on Twitter that Christopher Miller, Director of the National Counterterrorism Center, was taking over as acting secretary of defense.