President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE is butting heads with his military advisers as he attempts to pull back U.S. forces in Syria.



Trump’s instinct is to withdraw entirely, fulfilling his campaign promise to end nation-building and foreign entanglements.



But Pentagon officials and top generals have issued dire warnings about the possibility that terrorist groups will surge back in Syria if the United States leaves the country.



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A similar debate played out for months over Afghanistan, until Trump agreed to stay the course there indefinitely.In Syria, Trump has agreed to leave U.S. troops there for now, but gave the military a six-month deadline to finish the nebulously defined job of defeating the Islamic State in Iraq and Syria (ISIS).“One useful place to start is the different conceptions of war that Trump and his generals have,” said Stephen Biddle, adjunct senior fellow for defense policy at the Council on Foreign Relations. “Trump thinks wars should look like World War II. He’s looking for some sort of big dramatic blitzkrieg.

“He thinks that you win a war with some sort of sudden decisive violence, the enemy cries ‘uncle’ and then you have a big victory parade. That hasn’t been the way wars have worked for a long time. That’s kind of a cartoon idea of war.



“Trump’s generals at this point have lived through a generation of very hard experiments that has run this conception out of most of the American military. They think of wars as long, grinding, slow, often-indecisive struggles.”



The United States has about 2,000 troops in Syria. Pentagon officials say ISIS has lost about 90 percent of the territory it once held in Syria, but that it still needs to be routed from pockets along the Middle Euphrates River Valley and along the Syria-Iraq border.



Pentagon officials have also said that efforts to retake the last 10 percent of ISIS-held territory have stalled as the United States’s Kurdish partners have left the fight against ISIS to fight a Turkish incursion elsewhere in Syria.



Last week, Trump stunned an audience in a speech about infrastructure with a seemingly off-the-cuff remark that the United States will “be coming out of Syria, like, very soon.”



On Tuesday, he reiterated, “I want to get out. I want to bring our troops back home.”



Later on Tuesday, Trump met with his national security team. By Wednesday, White House press secretary Sarah Huckabee Sanders said in a statement that “the United States and our partners remain committed to eliminating the small ISIS presence in Syria that our forces have not already eradicated.”



Still, Sanders said the military mission “is coming to a rapid end, with ISIS being almost completely destroyed.”



The Pentagon on Thursday asserted that plans for Syria haven’t changed, denying that Trump set a six-month timeline during the meeting with his national security team.



“The president has actually been very good in not giving us a specific timeline, so that's a tool that we can use to our effect as we move forward,” Lt. Gen. Kenneth McKenzie, director of the Joint Staff, said during a briefing. “We've always thought that as we reach finality against ISIS in Syria, we're going to adjust the level of our presence there. So in that sense, nothing actually has changed.”



But before Trump’s proclamation, military and diplomatic officials had spoken for months about the need for a long-term military commitment in Syria.



At virtually the same time Trump was speaking Tuesday, his top commander in the Middle East and his top diplomat overseeing the international anti-ISIS coalition were across town delivering a different message.



“A lot of very good military progress has been made over the last couple of years, but the hard part, I think, is in front of us,” U.S. Central Command chief Gen. Joseph Votel said at a United States Institute of Peace event. “And that is stabilizing these areas, consolidating our gains, getting people back into their homes, addressing the long-term issues of reconstruction and other things that have to be done."



Before he was fired, former Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE delivered a speech, reportedly approved by Trump, that argued for a long-term military presence to ensure ISIS does not re-emerge, counter Iranian influence and keep the territory stable until a diplomatic process leads to Syrian President Bashar Assad’s removal.



“I think he’s bumping up against reality,” Danielle Pletka, senior vice president for foreign and defense policy studies at the conservative American Enterprise Institute, said of Trump. “I understand Donald Trump, like Barack Obama Barack Hussein ObamaTwitter investigating automated image previews over apparent algorithmic bias Donald Trump delivers promise for less interventions in foreign policy Rush Limbaugh encourages Senate to skip hearings for Trump's SCOTUS nominee MORE, wants to leave Syria. But under the circumstance that he has described, he can’t leave Syria. Any person who understands how counterterrorism works understands that.”



Trump’s dilemma has shades of former President Obama’s inability to end the United States’s wars.

Obama came into office pledging to end the Iraq War. When ISIS emerged, Obama pledged not to put boots on the ground in Iraq and Syria. He eventually left office with 500 ground troops in Syria and 5,000 in Iraq.



After an initial surge in Afghanistan, Obama also pledged to bring U.S. troops home from there. But on the advice of the generals, he left office with about 8,400 troops in Afghanistan.



“The reasons are very different, but the pattern is very similar,” Biddle said of the parallels between Obama and Trump, adding Obama was driven by a “psychodrama” between not wanting to wage war and following his advisers’ advice, while Trump is driven by “narcissistic, impulsive lashing out.”



Robert Ford, who was a U.S. ambassador to Syria in the Obama administration, said he thinks Obama and Trump are closer in thinking on Syria.



“Obama always viewed Syria as a kind of Shia-Sunni longtime battle in which America really didn’t have a dog in fight,” Ford said. “Obama just wanted to go pound ISIS and then leave. That’s not very different from Donald Trump.”



Trump’s advisers were able to change his mind about Afghanistan, but it remains to be seen whether they’ll successfully change his mind on Syria in the next six months.



As the deadline approaches, Trump and the military could be forced to grapple with the ill-defined nature of what it actually means to defeat ISIS.



“This is one of the problems that the national security team has had, and it predates Trump,” Ford said. “What is their definition of victory? What does defeating ISIS look like? Does it mean local security forces are able to contain ISIS? Is the definition that ISIS is so small that it can’t regenerate? If it’s local forces being able to contain them, which forces?”

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