FILE - In this June 7, 2017 file photo, Brett McGurk, the U.S. envoy for the global coalition against IS, speaks during a news conference at the U.S. Embassy Baghdad, Iraq. McGurk has resigned in protest to President Donald Trump’s abrupt decision to withdraw U.S. troops from Syria, joining Defense Secretary Jim Mattis in an administration exodus of experienced national security officials. AP Photo/Hadi Mizban)
FILE - In this June 7, 2017 file photo, Brett McGurk, the U.S. envoy for the global coalition against IS, speaks during a news conference at the U.S. Embassy Baghdad, Iraq. McGurk has resigned in protest to President Donald Trump’s abrupt decision to withdraw U.S. troops from Syria, joining Defense Secretary Jim Mattis in an administration exodus of experienced national security officials. AP Photo/Hadi Mizban) Credit: Hadi Mizban

Washington — Brett McGurk, the U.S. envoy to the international coalition fighting the Islamic State, has resigned in protest of President Donald Trump’s decision to abruptly withdraw U.S. troops from Syria.

His resignation, confirmed by a State Department official familiar with the matter, comes on the heels of Defense Secretary Jim Mattis’s announced departure last week over differences with the White House over foreign policy, immediately following Trump’s decision. Mattis said he would stay on until February to ensure a smooth transition.

Both Mattis and McGurk objected to what they saw as shortsighted decision and a breach of faith with U.S. allies including the Syrian Kurds, who fought alongside U.S. forces in Syria and now face a dangerous and uncertain future.

For Trump, the long-serving government officials are the first high-profile departures in protest of his policy decisions.

McGurk’s departure is effective on Dec. 31, an earlier exit than his intended departure in mid-February, the official said, speaking on condition of anonymity to discuss a personnel matter. McGurk submitted his resignation letter to Secretary of State Mike Pompeo on Friday, the official said.

The resignations send a negative signal to foreign partners whose support is crucial to containing Islamic State forces, said experts and former officials.

Earlier this month, McGurk said the Islamic State was far from defeated despite its loss of territory. “Nobody working on these issues day to day is complacent. Nobody is declaring a mission accomplished,” McGurk said at a State Department briefing. “Defeating a physical caliphate is one phase of a much longer-term campaign.”

McGurk, who was appointed to the job in 2015 by President Barack Obama and retained by Trump, had long maintained that the U.S. mission in Syria should retain a disciplined focus on countering the Islamic State rather than wider regional ambitions such as the overthrow of Syrian President Bashar al-Assad, said diplomats who worked with him over the years.

In theory, his preference for a modest U.S. role was aligned with Trump’s view, but McGurk disagreed with the president’s assessment that the threat posed by Islamic State had been eliminated.

In recent months, McGurk’s preference for a limited U.S. mission was overruled by other Trump advisers, in particular, national security adviser John Bolton, who vowed in September that the United States now had new goal in Syria aimed at countering Iran’s influence. “We’re not going to leave as long as Iranian troops are outside Iranian borders, and that includes Iranian proxies and militias,” he told reporters at the United Nations General Assembly in New York.

However, Trump last week ordered the withdrawal of all 2,000 or so U.S. troops from Syria and declared the Islamic State defeated. The move blindsided senior officials and ran counter to his own top aides’ advice, including that of Mattis.

“With the departures of folks like Secretary Mattis and Brett McGurk, you see indications that the experts felt so cut out of the process and so appalled by the decision that they simply couldn’t implement whatever the president’s vision is in a way that they could stomach, and so they chose to get out instead — in Brett’s case sooner than anticipated,” said Joshua Geltzer, who was White House counterterrorism senior director under Obama and is now a visiting professor at the Georgetown University Law Center.

The United States began airstrikes in 2014 against Islamic State strongholds in Syria, a country already torn by civil war since 2011. U.S. ground troops entered the country in 2015 to provide support to local forces fighting the militant group.

In addition to the Kurds, McGurk also valued U.S. partnerships with the British and the French, opposing a rapid withdrawal that left America’s commitment to those partners in limbo, said one diplomat, who was not authorized to speak about U.S. personnel.

At the time, Bolton and the new U.S. special representative for Syria, Jim Jeffrey, said the president was committed to a mission in Syria that kept U.S. forces there to ensure that the Islamic State doesn’t reemerge, but were never able to cite any memos or meetings in which the president expressed this view.

McGurk, who negotiated the 2011 U.S. withdrawal from Iraq for Obama, sought ways to forge alliances in a region rife with sectarian and other rivalries. He was, for instance, the driving force behind the creation of the Syrian Democratic Forces as a Kurdish-led force that also included Arabs — a move that he hoped would assuage Turkish concerns. The Syrian Kurdish militia, the YPG, is closely affiliated with the PKK, which is regarded as a terrorist organization by both Turkey and the United States.

The move, though, never fully satisfied any of the parties. And with the pending U.S. withdrawal from Syria, Turkey has sent signals it will move against the Kurds.

Nonetheless it was his tenacity and his personal touch in building relationships that served the counter-ISIS effort well, colleagues said. He met face-to-face with Kurdish and Arab leaders of the SDF, and was a constant presence in Baghdad and Irbil, the capital of the autonomous Kurdish region in northern Iraq, becoming the most recognizable American official in the country at a time when an Islamic State blitz threatened both capitals.

“At the end of the day he was focused on defeating ISIS,” said one former official, speaking on condition of anonymity because of the matter’s sensitivity. “All of his engagements make this (Syria decision) untenable because there’s a betrayal to foreign partners.”

McGurk’s departure in protest of the president’s Syria decision likely will complicate the counter-ISIS effort, said former officials.

“Anybody coming into this role will have a very difficult time being credible with our foreign partners,” said Nicholas Rasmussen, former director of the National Counterterrorism Center under Presidents Obama and Trump. “Obviously our diplomats are only as credible as the willingness of their country to live up to their commitments, and that has been undermined significantly in this case.”