The White House later confirmed that the US would move quickly to withdraw all its forces from Syria. "They're all coming back, and they're coming back now," Trump said in a video message.
Trump framed his decision to pull US troops out as the fulfillment of a campaign promise. The President was a longtime critic of the Obama Administration's policy on fighting Isis in Syria, writing in 2013 that the US "should stay the hell out of Syria".
2) Is that still the policy?
It's hard to say. After his announcement sparked a loud backlash, Trump extended his initial 30-day deadline for the pullout to four months - and then said publicly that he didn't approve of a four-month deadline, either. "I never said fast or slow," Trump insisted at a January 2 Cabinet meeting.
Trump's allies have also suggested that the pullout plans are up in the air. After a meeting with the President on December 30, Senator Lindsey Graham, R, told reporters that it was a "pause situation" rather than a pullout.
At the moment, it seems that no one really knows when a pullout might occur. During a visit to Israel yesterday, national security adviser John Bolton said that a number of objectives would have to be met before a withdrawal takes place. "The timetable flows from the policy decisions that we need to implement," he said.
And Trump appeared to contradict his own prior statements about the timing of any pullout. "I never said we're doing it that quickly," he told reporters.
3) Why was there so much resistance to withdrawing the troops?
Many of Trump's foreign-policy advisers and allies support a strong line against Iran and view the US presence in Syria as key to checking Tehran.
As recently as September, the State Department's special representative for Syria engagement, James Jeffrey, told reporters that the US mission in Syria included the departure of all Iranian military and proxy forces and the installation of a stable new government. "That means we are not in a hurry," Jeffrey said.
Among the Iran hawks was Defence Secretary Jim Mattis, who resigned the day after Trump announced his Syria move. In his resignation letter, Mattis said the President deserved a Pentagon chief who was "better aligned" with his views.
4) How many US troops are in Syria at the moment?
About 2200 US service members are in Syria at this time. Though the Pentagon has released little information about the deployment, some details have spilled out: During the push to retake the city of Raqqa, Isis' self-declared capital, in 2017, Special Operations forces and artillerymen were deployed there. Army Rangers also were sent to Syria to keep the peace between Syrian Kurdish fighters and forces loyal to Turkey.
There are also roughly 5200 US troops in neighbouring Iraq, where they assist the government in the fight against Isis. When Trump visited those troops on December 26, he suggested that "we could use this as the base if we wanted to do something in Syria".
5) Has Isis really been defeated?
The organisation has lost almost all of the territory it held at its peak in 2014 and 2015. The US-led military intervention that began during the Obama Administration has certainly helped with this, particularly the use of American air power.
But estimates released over the summer suggested that the group may still have more than 30,000 fighters in Syria and Iraq. Isis has shifted to insurgency tactics, carrying out kidnappings and assassinations in Iraq and defeating US-backed fighters in Syria. Some US military leaders have suggested that the group is well-positioned to re-emerge.
6) What effect could a pullout have on Syria's warring parties?
Turkey has emerged as a potential winner. The prospect of a pullout has deeply alarmed the Syrian Kurdish forces allied with the US. Turkey considers them terrorists and has vowed to drive them out of northeastern Syria. Bolton said that an agreement would be reached to keep the Kurds out of "jeopardy," but Kurdish officials have told reporters that they are seeking a deal with President Bashar al-Assad's Government just in case.
Any agreement with the Kurds would be a boon for Assad, who has retaken control of much of the country. It would also be a win for Assad's allies in Russia and Iran. The Trump Administration had earlier made countering Iran one of its key goals in the Middle East, but at a recent Cabinet meeting, Trump suggested that he wasn't worried about Iranian influence in Syria.
"They can do what they want," Trump said of Iran in Syria on January 3.
