Washington has ample reason to maintain a long-term military presence in eastern Syria, but it will need to overcome a host of political, legal, and logistical problems along the way.
The U.S. military recently announced that it has 2,000 troops in Syria, most of them working with the Syrian Democratic Forces (SDF), the Kurdish-dominated umbrella group that has liberated a large swath of the country's eastern provinces from the Islamic State. Now that conventional military operations against IS are essentially finished and international concerns about Iran are mounting, more attention is being paid to the future of the U.S. contingent and the estimated 40,000-50,000 SDF fighters associated with it. American forces could play an important role in reaching a Syria solution that curbs Iran's Russian-enabled power projection against Arab states, Israel, Turkey, and U.S. regional interests. Yet doing so requires that Washington deal with assorted challenges, from articulating the deployment's mission to clarifying its legal basis and mapping the diplomatic geography required to physically sustain it.
WHAT IS THE MISSION?
The best solution would be for the United States to continue justifying its presence in Syria (and Iraq) by emphasizing the need to prevent an IS resurgence—a goal that also requires restraining Iran's malignant actions in the region, which foster problems like IS in the first place. This means convincing both Congress and the international community that the threat is significant, as well as accommodating Turkish and Iraqi interests sufficiently to avoid dependency on either, thereby preventing a sudden shutdown of the deployment. Any such shutdown would be a bitter blow to the U.S. effort against Iran, increasing the chances of Israel or Saudi Arabia confronting Tehran and its proxies in their own uncontrollable ways.
Thus far, the Trump administration has sent mixed messages about its Iran policy. The most important element in the president's October 13 policy statement on Iran was not the much-hyped but largely symbolic decision to withhold certification of the nuclear deal, but rather the declaration that Washington would focus on containing Iran's "destabilizing activity" in the region. Since then, however, the White House has provided few details on the "how" of this policy.
On November 11, months after ending the U.S. military support program to Syrian rebels, President Trump signed a joint statement with Vladimir Putin that looked like a continuation of President Obama's failed policy of relying on deconfliction with Russia to contain Iranian efforts in Syria. While Moscow's interests are not completely aligned with Tehran's, they both aim to hijack the UN-sponsored Geneva process aimed at ending the war and undermine the U.S.-led regional security order.
On November 13, however, Defense Secretary James Mattis told reporters that U.S. troops in Syria are "not just going to walk away right now before the Geneva process has cracked...We're going to make sure we set the conditions for a diplomatic solution." To be sure, he was also careful to emphasize that the main mission is to keep IS from bouncing back, and this limited goal makes sense given that wider-scale U.S. policy missteps have contributed to the Syrian tragedy, facilitated Iranian expansionism, and allowed Russia to gain cheap reentry into the Middle East security realm. These missteps include failing to act on the U.S. chemical weapons "redline" in 2013, and failing to support relatively moderate rebel forces.
Yet the anti-IS mission can and should be interpreted more broadly as a mandate to restrain Iran and its client regime in Damascus, since their behavior largely provoked the rise of IS in 2013. While Russia seeks to undermine the entire Geneva process with its own military and diplomatic moves (e.g., the Astana and Sochi talks), UN Security Council Resolution 2254 makes clear that Syria's political future is a security concern for the entire international community. The criminality of the Assad regime's prosecution of the war -- from repeated use of barrel bombs and chemical weapons to mass population displacements -- cement the case for a robust U.S. and allied role.
Moreover, Washington and its partners still have potent assets in the Syrian arena and should leverage them fully. In military terms, the United States holds a strong position in the northeast via the SDF, while Turkey has a troop presence in the north and Israel frequently operates against Iranian and Hezbollah targets inside Syria. In economic terms, the SDF holds many of the country's oil fields, and wide-ranging postwar reconstruction is unthinkable without massive Western assistance, which Washington is wisely withholding until progress is evident in the peace talks.
Of course, having sufficient cause and assets does not mean that the mission will be easy. If Washington decides to maintain a military presence in Syria, it will face several pitfalls.
First, any such endeavor will necessarily be long term, messy, and uncertain, with no clear end state beyond containing Iran. As the military defeat of IS became imminent, Russia echoed Bashar al-Assad's calls for the United States to withdraw fully, while Iranian proxies launched pinprick attacks on U.S. and allied troops. Such complications are inherent to, and should be tolerable for, a limited-cost "light footprint" operation like the U.S. presence in Syria. As seen with Benghazi and Niger, however, public and congressional outcry can become deafening when these kinds of operations go awry, so the White House should be prepared to weather the storm.
A second pitfall is the issue of legal authority. Washington's deployment of forces in Syria and its support to the SDF rest on several mechanisms: the 2001 Authorization for Use of Military Force (AUMF) against al-Qaeda (given the Islamic State's genealogy as an al-Qaeda offshoot); Iraq's request for U.S. assistance under the bilateral 2008 Strategic Framework Agreement; Iraq's right of self-defense under Article 51 of the UN Charter; and various Pentagon train-and-equip authorities relating to counterterrorism. Thus, Secretary Mattis has framed a continued military presence in terms of defeating IS remnants, building up local forces to deal with an IS resurgence, and facilitating the Geneva process in order to prevent such a resurgence. Yet Congress has already questioned the 2001 AUMF's role in perpetuating "endless war," so it could oppose using that authorization to justify an open-ended military presence in Syria or specific operations targeting the Assad regime and Iran (e.g., the low-intensity clashes seen in May and June). On the international level, Assad could reinforce his increasingly strident calls for U.S. withdrawal by opening the matter up to UN debate.
Third, any U.S. contingent would face numerous logistical pitfalls. While American forces have established a handful of small Syrian enclaves abutting Jordan, the main U.S. presence is in the northeast, where access can only be obtained through Iraq, the Kurdistan Regional Government (KRG), or Turkey. For now, flying long distances over Assad-controlled territory is not a reasonable option because it would involve directly defying the regime, its Iranian proxy allies, and Russian air defenses. Convoying through regime territory would face similar problems. Yet the Iraqi and Turkish routes pose problems of their own. The current primary route, through the KRG, is shaky given Baghdad's demands to control or monitor Kurdish border posts, airports, and airspace following the disastrous KRG independence referendum in September. Prime Minister Haider al-Abadi is generally pro-American, but he will need to continue treading carefully given Iran's deep influence in Baghdad. It is unclear how long he would permit the United States to sustain a Syria presence that increases Iranian pressure on him without benefitting him directly.
For its part, Turkey shares Washington's interest in containing Iran but considers the U.S. alliance with the SDF to be anathema. The SDF is led by the Syrian Kurdish Democratic Union Party (PYD), which Ankara correctly regards as a wing of the Kurdistan Workers Party (PKK), the designated terrorist group that has waged a bloody thirty-year struggle against the Turkish government. Ankara adamantly opposes a strong PYD presence on its southern border, especially if the group is armed by the United States. U.S. relations with the SDF are further complicated by the group's occasional outreach to Russia.
Although Washington's apparent decision to halt arms transfers to the SDF has helped appease Ankara somewhat, Washington has generally done a poor job of managing Turkish cooperation in Syria. The Trump administration will therefore need to clarify its goals with the SDF and its broader plans for Syria if it hopes to gain active Turkish support for a continued U.S. military presence.
James F. Jeffrey is the Philip Solondz Distinguished Fellow at The Washington Institute and former U.S. ambassador to Iraq and Turkey.