Brett McGurk, the special presidential envoy for the Global Coalition to Defeat ISIS, has resigned effective Dec. 31, CBS News reports.

The big picture: McGurk was reportedly planning to leave his post in February 2019, but accelerated his resignation as a result of President Trump's decision to immediately withdraw U.S. troops from Syria. In a speech just one week before Trump's announcement, McGurk said, "It would be reckless if we were just to say, 'Well, the physical caliphate is defeated, so we can just leave now.' I think anyone who's looked at a conflict like this would agree with that."

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