US anti-ISIS envoy Brett McGurk has decided to step down at the end of December, following Secretary of Defense Mattis resigning. In a decision that moved up his expected leaving McGurk, who had served under Obama since 2015, has decided to leave early. This is an important symbolic decision. McGurk helped craft the Syria policy and his last pinned tweet was about stabilization in Syria.
He helped bring together the 74 nation Coalition. He was critiqued for his policy in October 2017 as Iranian-backed allies of Baghdad and Baghdad retook Kirkuk from the KRG, and he was accused of meddling in Iraqi politics and coalition building.