Who quit?
"Top US official in fight against Islamic State group quits over President Trump's decision to pull troops from Syria"
https://www.bbc.com/news/world-us-canada-46661384
"Brett H. McGurk is an American diplomat who was appointed by President Barack Obama on 23 October 2015 as Special Presidential Envoy for the Global Coalition to Counter ISIL. He replaced General John R. Allen to whom he had been a deputy since 16 September 2014."
-wiki