In a stunning turn in a four-day drama that has defined his young presidency, President Trump, at 9:16 p.m. Monday, announced the firing of the acting attorney general who had defied him on his migrant-travel ban, saying she "has betrayed the Department of Justice."

Until the confirmation of Jeff Sessions as attorney general, Trump named Dana J. Boente, a 31-year Justice Department veteran, as acting A.G.

Boente was sworn in within an hour of the announcement, AP reported.

Why Trump acted : Sally Yates, an Obama holdover, late Monday had ordered the Justice Department not to defend his controversial executive order imposing a 90-day ban on entry to the US. by citizens of seven predominantly Muslim countries.

: Sally Yates, an Obama holdover, late Monday had ordered the Justice Department not to defend his controversial executive order imposing a 90-day ban on entry to the US. by citizens of seven predominantly Muslim countries. What Yates wrote in a letter to department lawyers: "I am not convinced that the defense of the Executive Order is consistent with these responsibilities nor am I convinced that the Executive Order is lawful."

"I am not convinced that the defense of the Executive Order is consistent with these responsibilities nor am I convinced that the Executive Order is lawful." The backdrop: The speed and severity of Trump's measure, which he calls the simple enactment of a signature campaign promise, has been criticized by some CEOs, Republican lawmakers and crucial allies, and prompted massive weekend demonstrations at airports around the country.

The speed and severity of Trump's measure, which he calls the simple enactment of a signature campaign promise, has been criticized by some CEOs, Republican lawmakers and crucial allies, and prompted massive weekend demonstrations at airports around the country. The successor: Boente was nominated by President Obama in 2015 to be U.S. Attorney for the Eastern District of Virginia, based in Alexandria. Boente is a graduate of St. Louis University and its law school, and has lived in Northern Virginia for 29 years, according to his official bio.

Here is the text of the White House announcement, emailed to reporters:

Statement on the Appointment of Dana Boente as Acting Attorney General

The acting Attorney General, Sally Yates, has betrayed the Department of Justice by refusing to enforce a legal order designed to protect the citizens of the United States. This order was approved as to form and legality by the Department of Justice Office of Legal Counsel.

Ms. Yates is an Obama Administration appointee who is weak on borders and very weak on illegal immigration.

It is time to get serious about protecting our country. Calling for tougher vetting for individuals travelling from seven dangerous places is not extreme. It is reasonable and necessary to protect our country.

Tonight, President Trump relieved Ms. Yates of her duties and subsequently named Dana Boente, U.S. Attorney for the Eastern District of Virginia, to serve as Acting Attorney General until Senator Jeff Sessions is finally confirmed by the Senate, where he is being wrongly held up by Democrat senators for strictly political reasons.

"I am honored to serve President Trump in this role until Senator Sessions is confirmed. I will defend and enforce the laws of our country to ensure that our people and our nation are protected," said Dana Boente, Acting Attorney General.

Earlier story: The Trump bulldozer

We can't stress this enough: Watch closely the specific, substantive moves of the Trump White House. Try to block out the white noise of outlandish statements and unforced errors, and the hyperventilating they provoke. This is more a bulldozer than a runaway train.

Update: Boente canceled Yates' earlier order.