Brett McGurk, U.S. special presidential envoy for the global coalition to defeat the militant group, submitted his resignation effective Dec. 31 to Secretary of State Mike Pompeo on Friday, a State Department official said. In an abrupt policy shift, Trump announced on Wednesday that Washington would withdraw the roughly 2,000 U.S. troops in Syria, upending a pillar of American policy in the Middle East and alarming U.S. allies. The decision was followed on Thursday by the surprise departure of U.S. Secretary of Defense Jim Mattis, who in a resignation letter to Trump laid bare the growing divide between the two over foreign policy. McGurk, who was slated to leave his post in February 2019, objected to Trump's decision to withdraw U.S. troops from Syria, a person familiar with the matter said, and added that Mattis' departure had a "significant impact" on McGurk's resignation. Trump, for his part, tweeted late Saturday that McGurk had simply moved up the date...