Brett McGurk, the top US official leading a 79-nation coalition fighting ISIS, resigned from his post on Friday in protest of the president's sudden decision to withdraw all US troops from Syria.

the president's sudden decision to withdraw all US troops from Syria. McGurk said in an email to staff that President Donald Trump's decision on Syria came as a "shock," was a "complete reversal" of US policy, and "left our coalition partners confused and our fighting partners bewildered."

said in an email to staff that President Donald Trump's decision on Syria came "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," he wrote.

Brett McGurk, the top US official leading a 79-nation coalition fighting ISIS, resigned from his post on Friday in protest of President Donald Trump's sudden decision to withdraw all US troops from Syria, telling staff in an email that Trump's move came as a "shock" and a "complete reversal" of US policy.

"It left our coalition partners confused and our fighting partners bewildered," McGurk wrote in the email, which the New York Times' Rukmini Callimachi reported brought some staffers to tears.

McGurk, the special presidential envoy in the long-fought battle, was planning to retire in February, but sped up his departure as a result of the president's controversial and unexpected decision to pull all 2,000 US troops out of the war-torn Middle Eastern nation, CBS News reported on Saturday.

He wrote in the email, which was first reported by the Times, that he could not abide the dramatic change in policy, which Trump announced by tweet without consulting Congress or US allies. "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," he said. Read more: 13 intense images of the rise and fall of ISIS, the feared terror group that has re-surged from previous defeats McGurk's resignation comes just one day after Secretary of Defense James Mattis announced he is quitting over Trump's withdrawal from Syria, treatment of US allies, and the handling of American adversaries.

Just days ago, McGurk, a rare Obama administration holdover who has served three presidential administrations, said US forces would remain in Syria until "we have the pieces in place to ensure that that defeat is enduring."

"It would be reckless if we were just to say, well, the physical caliphate is defeated, so we can just leave now," he said at the State Department podium. "I think anyone who's looked at a conflict like this would agree with that."

On Saturday, Trump called news reports concerning Syria "mostly FAKE" and insisted that the terrorist group is "largely defeated" and can be contained by neighboring countries, including Turkey, despite the fact that the group retains as many as 30,000 loyal fighters.

"When I became President, ISIS was going wild. Now ISIS is largely defeated and other local countries, including Turkey, should be able to easily take care of whatever remains," Trump wrote. "We're coming home!"

—Face The Nation (@FaceTheNation) December 22, 2018