When U.S. President-elect Donald Trump is inaugurated on January 20, 2017, his most complicated foreign policy challenge will be what to do about Syria. Under President Barack Obama, Washington’s Syria policy has focused on fighting the Islamic State of Iraq and Syria (ISIS). But with ISIS teetering, the government of Bashar al-Assad gaining ground, and outside powers such as Iran and Russia becoming ever more involved, simply fighting the caliphate may not be enough for the next leader of the United States.
In order to destroy ISIS and uproot the extremism that has been generated by the Syrian war, the United States will need to help stabilize opposition-controlled areas of the country while pressuring Iran and Russia to move toward a viable political settlement. To get there, President Trump will need to be more willing to put pressure on Moscow and Tehran than he has so far indicated. That means he should be ready to impose penalties on both if they do not fulfill any commitments they make.
A FRAGILE EQUILIBRIUM
Today, ISIS and the Assad regime each control roughly one-third of Syria. Thanks to help from Russia and Iranian-backed Shiite militias, the Syrian government has established control over what it calls “essential Syria”: the urbanized, north–south spine of the country that connects Damascus to the country’s largest city, Aleppo, which Assad is now on the verge of reconquering. But if he is successful, what happens next is unclear. Assad claims he will reassert control over the entire country, but he lacks the manpower to take and hold Sunni-dominated territory in northwestern, eastern, and southern Syria. He could only do so by importing more Shiite militiamen from abroad, which could provoke Syria’s neighbors to increase their involvement and fuel the local Sunni insurgency.
Eastern Syria has, for the last two years, been split between ISIS and the Kurdish People’s Protection Units (YPG), part of the Syrian wing of the Turkish Kurdistan Workers’ Party (PKK), which Ankara considers