Sean Rossman | USA TODAY

AP

Hadi Mizban, AP

President Donald Trump's decision to withdraw U.S. troops from Syria drew the Friday resignation of Brett McGurk, the top U.S. envoy fighting ISIS, reports say.

McGurk's decision came a day after Defense Secretary Jim Mattis resigned over Trump's abrupt decision to remove the special operations troops, who had been training local security forces fighting ISIS terrorists.

McGurk, who was appointed by former President Barack Obama in 2015, was expected to retire in February but instead resigned in the wake of Trump's decision, the Associated Press and CBS reported.

"The recent decision by the president came as a shock and was a complete reversal of policy that was articulated to us," he emailed colleagues, according to The New York Times. He added that the decision left partners in the fight against ISIS "confused" and "bewildered."

Trump's announcement Wednesday for a U.S. withdrawal from Syria went against the objections of his military advisers. The president based his decision on the notion that the mission against ISIS is completed, a U.S. official told USA TODAY.

Mattis resigned the next day. He told the president in a letter he was stepping down so the president could hire a defense secretary "whose views are better aligned with yours."

Evan Vucci, AP

Before Trump's announcement, McGurk said it would be “reckless” to consider ISIS defeated and argued it would be unwise to bring American forces home.

“I worked this week to help manage some of the fallout but – as many of you heard in my meetings and phone calls – I ultimately concluded that I could not carry out these new instructions and maintain my integrity,” said McGurk's email, according to the Times.

James Comey, who was fired by Trump as FBI director, weighed in on Twitter on this week's double resignations: "To a president without any external ethical framework, folks who resign on principle must be confusing."