Nader Uskowi is a nonresident senior fellow with the Atlantic Council’s Scowcroft Center for Strategy and Security.
Iran-led forces present arguably the greatest future threat to U.S. military personnel and overall interests in Syria, and therefore must be the centerpiece of a broader strategy addressing the conflict.
As U.S.-led coalition forces approach victory against the self-proclaimed Islamic State caliphate in Syria, a new battlespace is emerging that will involve warring factions vying for control of IS-held territories. These lands stretch from Raqqa through the Euphrates River Valley to the border with Iraq and the Syrian Desert, known as the Badiya. Shia militias, led by the Qods Force of Iran's Islamic Revolutionary Guard Corps, will be particularly aggressive in their quest to control the crossing points on the Syria-Iraq border and seize terrain on the Syrian side.
Combined with clearing Iraq's western border region, Iran-led forces will control supply lines through Iraq linking the Islamic Republic to Syria and Lebanon, lines that are vital to transporting Shia fighters, weapons, and materiel. The U.S.-backed Kurdish and Arab Sunni forces will also fight to control the IS-held terrain with the goal of securing a stake in a future Syria -- or its territories, should the country fracture. The emerging conflict between the Iran- and U.S.-backed forces in the area will be a major component of the new battlespace.
Whereas the United States first intervened militarily in Syria in 2014 to defeat the Islamic State, the realities of a post-caliphate era call for a new U.S. policy. Countering the Iran-led military campaign in Sunni-populated areas could well be the cornerstone of such a policy.
Origins of U.S. Military Intervention in Syria
In September 2014, the Islamic State attacked Kobane, one of three Kurdish cantons in northern Syria that constitute an autonomous region the Kurds call Rojava. The People's Protection Units (YPG) -- the armed wing of the Kurdish Democratic Union Party (PYD) -- led the fight. They asked for U.S. support: airstrikes against IS targets and the deployment of Special Forces to arm, train, advise, and assist YPG fighters. The Obama administration was thus finally drawn into the war in Syria, albeit defined narrowly as a "defeat IS" campaign. Indeed, IS forces had provided such an opportunity, exposing themselves to airstrikes in Kobane, an opportunity of which the United States took full advantage.
On the ground, the YPG waged a spirited battle, televised live around the globe, and by January 2015 the Kurdish fighters had liberated Kobane. In the process, the YPG became the favorite ground force of the U.S.-led anti-IS campaign in Syria. The U.S.-YPG alliance thereafter set a high goal of liberating the city of Raqqa, the de facto Islamic State capital in Syria. In June 2017, YPG fighters and their Sunni Arab allies, under the banner of the Syrian Democratic Forces -- backed by U.S. airpower and Special Forces -- breached IS defenses and entered Raqqa's outer neighborhoods.
The Southern Front
As the Islamic State faced defeat in the north, the southern front gained importance amid a shrinking battlespace. U.S. partners in the south consisted of Sunni Arab opposition groups trained to defeat IS but with their eyes on pro-regime forces set on reclaiming Sunni-majority territory in a post-caliphate Syria.
Drawing alarm in May 2017 was a mechanized column of Shia militias, operating under Iran's Qods Force and its commander, Gen. Qasem Soleimani, which penetrated the declared thirty-four-mile deconfliction zone around the Syria-Iraq border crossing of al-Tanf. The border town -- home to U.S.-backed Syrian opposition fighters who had liberated the outpost from IS last year -- is a garrison for U.S. and allied special forces who advise and assist the opposition.
On May 18, U.S. fighter jets struck the convoy as it advanced toward the base, probably with the aim of outflanking and isolating coalition forces, and destroyed Iran-supplied armored vehicles and killed militia fighters. Hindering full Qods Force access to its area supply lines is rebel control of an outpost along the main Baghdad-Damascus highway. Days later, meanwhile, U.S. forces shot down an Iranian armed unmanned aerial vehicle (UAV) attacking U.S. and opposition fighters in the al-Tanf area. The incident demonstrated the willingness of the Qods Force to directly confront U.S. assets in Syria as well as a new willingness by the United States to respond to Iranian provocations in the country. On June 19, U.S. forces were again compelled to shoot down an Iranian UAV near the al-Tanf garrison.
Alongside the immediate border region, another entrant to the new battlespace is the Euphrates River Valley. On June 18, a Syrian fighter jet attacked U.S.-backed forces south of Raqqa -- an area in which Syrian forces back Qods Force-led operations -- prompting U.S. forces to shoot down the plane. Iran also launched ballistic missile attacks on IS targets in the valley, including in the city of Deir al-Zour, ostensibly avenging recent terrorist attacks in Tehran but undoubtedly signaling to all its opponents, including the United States and its allies, its intention to compete in the area after the Islamic State falls.
The Changing Battlespace
With the dramatic rise of IS in 2014, the Syrian battlespace soon consumed the entire country, drawing in major powers and regional actors at unprecedented levels. The U.S. anti-Islamic State campaign began in Kobane during that period. Three years later, IS's looming defeat in Raqqa moves the spotlight to the Badiya, the Syria-Iraq border region, and the Euphrates River Valley. In these areas, rivalry and conflict will play out among the many actors operating in the shrinking battlespace that previously constituted IS territory.
Iran-led forces, under Soleimani's command, will present arguably the greatest future threat to U.S. military personnel and interests in Syria. In the Iraq-Syria border region, Iran is executing a strategy centered on establishing a land bridge to Syria through Iraqi territory. Such a plan will inevitably cause direct conflict with U.S.-backed Sunni opposition forces that must control the Badiya and Euphrates River Valley to play a role in a future Syria. The U.S.-backed Arab Sunni opposition's big battles will thus be fought against the Qods Force-led Shia militias in the desert. For the time being, Iran-led units will continue targeting the isolated garrison in al-Tanf in a bid to persuade the United States that holding it would be impractical. Soleimani would consider U.S. withdrawal from al-Tanf to be a strategic as well as a moral victory for Iran. Meanwhile, on the Iraqi side, the Qods Force-led Shia Popular Mobilization Units are clearing areas west of Mosul to establish direct links from territory around Sinjar north to Hasaka, constituting the northern land bridge, and south toward al-Qaim and Abu Kamal to stage operations in the Euphrates River Valley.
Need for a New U.S. Policy
The initial U.S. policy aimed narrowly at defeating the Islamic State is now largely being accomplished. The new battlespace in formerly IS-held territories, however, calls for a new U.S. policy, the chief component of which should be a strategy targeting Iran's Qods Force and its Shia militias. For their part, U.S. officials appear to understand clearly the threat posed in the coming weeks and months by the Iran-led campaign, and have the military capability to respond. To be sure, continuing under the confines of a mere anti-IS campaign would work against broader U.S. interests. In particular, any aggressive moves by the Iran-backed pro-regime forces in the area could be interpreted as dovetailing with the U.S. opposition to IS, even though the Iranian strategy unmistakably focuses on defeating U.S.-supported opposition forces and pushing the United States out of Syria. Absent a new strategy that addresses Iran's involvement in Syria, U.S. and allied forces could, at best, resort to self-defense tactics when under attack. In the process, such relative passivity could embolden Iran to raise the temperature in hopes of booting U.S. forces from the country.
A complicating factor is Russian support for the Iran-sponsored Shia militia campaign in the area. Thus, a well-defined U.S. strategy to counter Qods Force activities in the majority-Sunni region is a prerequisite for enticing Russia to help constrain Iran's actions in the area, or at least not support them. Iran-led forces are, with strong backing from Russia, already in control of Alawite-led western Syria. Their expansion into the Sunni-majority east and south could prolong the civil war and risk widening it further, more overtly pitting major powers against each other. Such an outcome should please Moscow no more than it would Washington. The United States must therefore firmly uphold the premise that once the IS caliphate falls, the majority-Sunni east and south are for the Sunnis to manage. Any attempt by Iran to extend the Sunni-Shia conflict into those regions should be stopped in its tracks.
Nader Uskowi is a visiting fellow at The Washington Institute and the senior policy advisor to U.S. Central Command.