President Donald Trump announces via Twitter on Monday that he has replaced Defense Secretary Mark Esper with a new acting secretary, Christopher Miller, who had been confirmed by the Senate as the director of the National Counterterrorism Center.

President Donald Trump announces via Twitter on Monday that he has replaced Defense Secretary Mark Esper with a new acting secretary, Christopher Miller, who had been confirmed by the Senate as the director of the National Counterterrorism Center.
I am pleased to announce that Christopher C. Miller, the highly respected Director of the National Counterterrorism Center (unanimously confirmed by the Senate), will be Acting Secretary of Defense, effective immediately..
— Donald J. Trump (@realDonaldTrump) November 9, 2020
…Chris will do a GREAT job! Mark Esper has been terminated. I would like to thank him for his service.
— Donald J. Trump (@realDonaldTrump) November 9, 2020