▶ Watch Video: Trump fires Secretary of Defense Mark Esper

The upheaval in the Pentagon in President Trump’s final weeks in office began with the firing of Defense Secretary Mark Esper on Twitter, but it didn’t end there.

In the hours after, the Under Secretary of Defense for Policy James Anderson, Under Secretary for Intelligence Joseph Kernan, and Esper chief of staff Jen Stewart all resigned. 

Anderson’s release was sudden — he resigned before he could be fired — but Kernan’s had been planned. Stewart is being replaced by Kash Patel, a controversial former aide to Republican Representative Devin Nunes. 

Kernan is one of the most important intelligence officials in U.S. government, since the Pentagon has authority over both the National Security Agency and the National Geospatial Agency. 

Anthony Tata will assume the responsibilities of the Under Secretary for Policy. Tata had been nominated for that job, but the White House withdrew his nomination after the Senate Armed Services Committee made it clear it would not confirm him because of some previous tweets promoting a conspiracy theory.

The swift changes come at a critical time for the country, as President Trump refuses to concede and the general services administrator refuses to acknowledge Biden is the winner, rendering coordination between the incoming administration and the current administration non-existent.

Esper fell out of favor with the president months ago, and there have bee reports for several weeks that Mr. Trump was preparing to fire him after the election. An NBC News report last week that Esper had prepared a letter of resignation prompted a denial by the Pentagon, with a spokesperson saying he had no plans to step down. 

David Martin and Kathryn Watson contributed to this report.