WASHINGTON — President Donald Trump announced Monday on Twitter that he has "terminated" Defense Secretary Mark Esper, replaced by Christopher C. Miller, director of the National Counterterrorism Center.
The announcement came about five months after he and his Pentagon chief had a public break over how to handle civil unrest in America's cities.
"Mark Esper has been terminated," Trump tweeted. "I would like to thank him for his service."
A Defense Department spokesperson declined to comment and referred CNBC to the White House.
In another tweet, Trump said Miller will serve as acting secretary, effective immediately.
Miller, who previously spent 31 years in the U.S. Army, was sworn in as director of the National Counterterrorism Center in August. Before that, he served as Deputy Assistant Secretary of Defense for Special Operations and Combating Terrorism. In that role, he was responsible for overseeing the employment of special operations forces in counterterrorism as well as personnel recovery and hostage issues.
It is unlikely the Senate will confirm Miller or a new nominee for the role before Trump leaves office in January.
A spokesman for the Biden transition team declined to comment on Esper's dismissal.
The moves come as Trump refuses to accept the results of the presidential election and on the heels of an NBC News report that Esper had prepped his resignation letter, bracing for an inevitable termination from the Trump administration.
Esper's firing might not be all. A Trump administration official told CNBC's Eamon Javers that "I assume FBI and CIA are next," referring to FBI Director Christopher Wray and CIA Director Gina Haspel.
In an extraordinary break with Trump, Esper told reporters in June that he did not support the invoking the Insurrection Act, an 1807 law, to allow Trump to deploy active-duty U.S. troops to respond to civil unrest stemming from protests against police brutality across the country.
"I say this not only as secretary of Defense, but also as a former soldier and a former member of the National Guard, the option to use active-duty forces in a law enforcement role should only be used as a matter of last resort, and only in the most urgent and dire situations. We are not in one of those situations now," Esper said.
Hours after Esper's statement, White House press secretary Kayleigh McEnany said Trump has the "sole authority" to move forward with the measure. When asked if the president was peeved by Esper's comments at the Pentagon, McEnany gave a lukewarm response.
"I would say if he loses confidence in Secretary Esper I'm sure you all will be the first to know. As of right now, Secretary Esper is still Secretary Esper, and should the president lose faith, we will all learn about that in the future," McEnany said at the time.
Esper, who was previously the secretary of the Army, ascended to Pentagon chief in June 2019.
His tenure followed the resignations of Trump's first secretary of Defense, James Mattis, and then-acting Secretary Patrick Shanahan.
Much like Shanahan, Esper ascended to the top spot of the largest federal agency with limited experience in foreign policy.
Before becoming Defense secretary, Esper was a Raytheon executive. He left the defense giant to become secretary of the U.S. Army in 2017.
He is a graduate of the U.S. Military Academy and served in the 1990-1991 Gulf War with the Army's 101st Airborne Division. Following active duty, he served in the Army Reserve and both the Virginia and District of Columbia National Guard before retiring in 2007.
— CNBC's Kevin Breuninger contributed to this report.