United States President Donald Trump has fired Defense Secretary Mark Esper in his first big personnel action after his defeat was announced.

"Mark Esper has been terminated," Trump said in a tweet on Monday. He said that he was replacing him with Christopher C. Miller, director of the National Counterterrorism Centre, as the acting defense secretary.

Esper's dismissal presages the chaos that will engulf the administration during the transition to Democrat Joe Biden's presidency.

Donald Trump
Donald Trump addressing the nation at the White House on Wednesday. Twitter

Reacting to the dismissal, Chris Murphy, a Democrat on the Senate Foreign Relations Committee, tweeted a warning, "Trump is creating a dangerously unstable national security environment during this transition period. Adversaries are watching."

Was Esper Preparing to Quit?

News reports last week said that Esper was preparing to quit on his own after the election results are announced, but Trump appears to have preempted it by announcing the dismissal.

Esper was the army secretary when he was tapped by Trump to become the defense secretary and was confirmed by the Senate last July.

He was Trump's second defense secretary, succeeding Jim Mattis, who resigned less than a year on the job. He resigned over opposition to Trump's plans to withdrew US troops from Syria and Trump force his out a month before the resignation was to become effective.

Trump initially nominated a former Boeing executive and deputy defense secretary Patrick Shanahan to succeed Mattis, but he withdrew after allegations of domestic abuse surfaced.

Esper had served as an army officer in Iraq and Afghanistan and later worked for think tanks and the defense manufacturer Raytheon.

Mark Esper
U.S. Defense Secretary Mark Esper Wikimedia Commons

Trump and Esper had several differences, the most important of which was about Trump's proposal to use the armed forces against protesters, which is constitutionally prohibited. Trump backed down.

Asked at a news conference in August, Trump said, "I consider firing everybody. At some point, that's what happens."

He said at an election rally this month that he would consider firing Anthony Fauci, the nation's authoritative official dealing with the COVID-19 crisis, after the doctor has been critical of how Trump deals with the pandemic.

Trump said of his plan to fire Fauci, "Don't tell anybody, but let me wait until a little bit after the election."

Biden said that he would hire him, but he is not on the panels that he announced on Monday to fight the coronavirus, because Fauci is a civil servant as the director of the National Institute of Allergy and Infectious Disease.

As that is not a political appointment and the job has civil service protection, Trump will find it difficult to fire Fauci.