The Turkish government has threatened to invade Afrin, a Kurdish-dominated enclave in northwestern Syria. What explains this impending escalation in Syria’s internationalized civil war?

The Turkish threat follows a U.S. announcement that troops in Syria would create a “Border Security Force,” culled from the ranks of its main partner on the ground, the YPG and the group’s allied Arab militias. The announcement prompted a fierce reaction in Turkey, and ultimately culminated in Ankara’s threat to use military force. Turkish President Recep Tayyip Erdogan coupled that threat with another against American forces working with the YPG. In a speech at the opening of a power plant in Ankara, Erdogan said:

take down the flags on the terrorists yourselves so that we do not have to hand over those flags to you. Remove your badges from your uniforms of the terrorists so that we are not forced to bury those who act with the terrorists.

The U.S. military walked back its Border Security Force announcement days later, no doubt to try and ease tensions with Ankara. However, it would be a mistake to assume that Ankara’s plans to invade Afrin are solely linked to the name given to repurposed U.S. supported ground forces. Instead, the Turkish threat is the culmination of years of tensions with Washington over Syria policy in general, and divergences over how best to fight the Islamic State, or ISIL. The real issue is that the Trump administration has rolled out a Syria policy that gives the Syrian Democratic Forces (SDF), the YPG dominated umbrella grouping of militias, an open-ended, de facto U.S. security guarantee. This is a problem for Turkey because the YPG is the Syrian branch of the Kurdistan Workers’ Party (PKK), an insurgent group active in Turkey since the early 1980s.

In his testimony to the Senate Foreign Relations Committee, Acting Assistant Secretary for Near Eastern Affairs David Satterfield stated that the Trump administration does not intend to “leave Syria, or to declare victory and go” and that the reasons for staying are “stabilization assistance in the north and northeast, protection of our allies, the Syrian Democratic Forces, who have fought so valiantly against ISIL in the northeast, and to try and work to transform the political structures in that area to a model for the rest of Syria, and capable of being represented in a new Syrian state” and to “counter Iran.” Secretary of State Rex Tillerson echoed these words in his Syria policy speech at the Hoover Institution.

The Turkish government used the Border Security Force announcement as a pretext to justify long-standing military plans, aimed at thwarting what Ankara sees as a serious threat on its border. However, Ankara does not have total freedom of action in Syria. Turkey is constrained by the United States and Russia, two more powerful external actors present in Syria, both of whom have forces deployed in Kurdish dominated areas.

To put all this into context, let’s review the lay of the land.

The Syrian Kurds control northeastern Syria and work with select Arab partners (not without some challenges) to govern cities and towns to the west and east of the Euphrates river. Afrin is located in northwestern Syria and is surrounded on all sides by the Turkish military. The U.S. military has no presence in Afrin. Russia has deployed military police in the enclave and controls the airspace overhead, which makes them the dominant external actor in this part of Syria.

What does all this mean? As the war against ISIL subsides, Washington is focused on securing territory in Syria and preventing a return of the Islamic State. The United States has clearly signaled that it intends to rely on the SDF to patrol and police territory taken from ISIL. The United States intends to continue training the SDF as the force that will patrol the Turkish border, a fact the made clear in a U.S. military statement. In any case, Turkish Foreign Minister Mevlu Cavusoglu dismissed the U.S. statement, signaled that military action was still imminent, and indicated that Turkey expects the United States to re-evaluate its support for the SDF.

Turkey’s escalating rhetoric has prompted pushback from the Syrian regime. Deputy Foreign Minister Faisal Meqdad, warned that “[t]he Syrian air defenses have restored their full force and they are ready to destroy Turkish aviation targets in Syrian Arab Republic skies.” The regime’s propaganda outlet, Al Masdar News, also wrote that YPG forces have traversed regime territory to reinforce positions in Afrin in preparation for the expected intervention. The regime, however, has demonstrated an inability to defend its borders and often makes threats it cannot carry out. However, the threat could help to give cover to Russia, whose permission Ankara needs to launch a cross-border intervention in a territory where Russian soldiers are present.

The Syrian regime’s threat could give Moscow room to push back against Turkey by claiming that it cannot control the whims of it client — and that the regime is within in rights to take steps to defend itself. Turkey must solve these complicated dynamics before it invades, or risk unintended escalation and a much larger conflict than it is now planning for.

The Turkish government is diligently working to secure Russian permission to conduct air operations in support of the planned cross-border offensive. Turkey’s chief of the General Staff, Hulusi Akar, and the director of its national intelligence agency, Hakan Fidan, travelled to Moscow yesterday, presumably to brief their Russian counterparts on Ankara’s battle plans. Turkey’s hesitance to bash Russia for its position on the Syrian Kurds compared to its public bashing of the United States, is typical. Gonul Tol, writing last month for War on the Rocks, noted that Erdogan is promiscuous in his verbal attacks on the United States for working with Syrian Kurdish forces, but when it comes to Russian meddling with the Kurds, “Ankara is mute.” More broadly, the power dynamics underscore how Turkey is cementing itself as Moscow’s junior partner in Syria and how its interests in the conflict have narrowed, to focus primarily on the Kurdish threat.

A Quadripartite, Anti-Kurdish Partnership or More of the Same?

The broader question is whether powers hostile to the United States — namely Iran, Russia, and the Assad regime — will try to capitalize on Ankara’s poisonous rhetoric and co-opt Turkey to join an alliance of convenience aimed at pushing the United States to withdraw from Syria. In response to the initial Border Security Force announcement, Russia, Turkey, and the Syrian regime issued similar condemnations. It is easy to see why: A prolonged U.S. presence, committed to protecting borders suggests an intent to formalize the current front lines, a process that further could limit Assad’s ambitions to once again rule the entire country.

On the surface, Turkey does share some interests with Russia, Assad, and Iran vis-à-vis the U.S.-SDF partnership, but there is enough to divide them that could limit the formation of an anti-American alliance of convenience.

Turkey and Iran, for example, have an interest in weakening the PKK. The group’s Iranian branch, PJAK, is a minor threat to the Islamic Republic and the two countries have previously worked together on border security. In Syria, the twin threats posed by an empowered SDF and the potential for the Syrian state to break up could theoretically catalyze deeper Iranian-Turkish cooperation to undermine SDF territorial control. The Turkish government, however, often accuses Iran of enabling the PKK when it has an interest in punishing Turkey, so there are natural limits to a broader Turkish-Iranian consensus, built around a joint effort to oust the United States from Syria.

Russia also has an interest in an American withdrawal from Syria to shore up its ally in Damascus while undermining the United States in the Middle East. Further, Moscow would like to weaken NATO by driving a deeper wedge between the United States and Turkey. However, Moscow has also maintained relations with the YPG and may seek to broker a regime —Kurdish rapprochement as part of a broader effort to stabilize the country in the near future. Turkey may be silent about this cooperation, but it is still a reality. Washington has a similar interest in managing regime-SDF tensions and preventing the expansion of the war to new areas, but, of course, Washington differs with Russia on the Assad question.

Russian ties to the YPG may explain Moscow’s hesitation to fully support a Turkish invasion. Moscow’s geopolitical benefits in an open-ended conflict involving a NATO member are easy to understand: Turkey risks getting bogged down in an insurgent conflict it cannot win against a U.S.-backed group, while also assuming responsibility for administering and financing territory in a war-torn state for the foreseeable future. Tempting as this may be, a Turkish presence also risks widening a war Russia is trying to wind down and will certainly complicate future efforts to convince a hostile Assad regime to make concessions to different parties to the conflict. Moscow is a party to the civil war and, presumably wants to wind down its own military operation at some point in the future.

There are also more immediate reasons to doubt the formation of a quadripartite anti-American group in Syria. The Syrian regime’s relationship with Ankara is awful and Damascus has a more immediate interest: defeating the Turkish backed insurgency. Iran shares this goal and both have made clear that they intend expand the war to break the sieges of Fua and Kafrya, two Shiite majority villages. This would further strain previous Russian, Turkish, and Iranian efforts to reach a de-escalation agreement in the area, although the Idlib de-escalation arrangement was rife with contradictions and is likely to collapse all on its own. The Turkish government supported the effort, so it should be expected to react negatively to an Iranian-backed offensive that runs counter to the agreement.The regime should then be expected to want to take back control over its borders with Turkey to prevent the overt supply of weapons to proxy groups committed to toppling Assad. The trajectory of the war signals that it is headed for Turkey’s border with Idlib, whether Ankara invades Afrin or not.

Russia is being pulled in both directions. It operates as part of a coalition that is fighting groups committed to toppling the regime. Moscow is unlikely to be able to convince its partners to make positions that could result in Assad’s death. Washington too, gets a vote and should be expected to resist any effort to marginalize its role in diplomatic talks and to double-down on its presence in Syria to protect its partner on the grounds and, theoretically, to increase U.S. leverage over the other external actors.

The Bigger Picture: A Geopolitical Mess and Turkey’s Place in It

An open-ended military presence in SDF-controlled Syria is a recipe for U.S.-Turkish tensions. Moscow benefits from U.S.-Turkish tensions and has deftly managed to use the broader policy disagreement about Syria to its advantage. However, Russia is also having to balance relations with Turkey and the YPG. If one zooms out, Russia remains in alliance with Damascus, while Turkey continues to pump money and guns to an opposition that is hostile to the Assad regime. Turkey has narrowed the focus of its Syria policy in recent months and is now primarily focused on challenging the YPG. This policy change has de-emphasized Ankara’s previous policy of regime change.

However, there are limits to Turkish actions that prevent Ankara from completely giving up on the anti-Assad opposition. Turkey controls a swathe of territory in Northern Aleppo and is propping up parallel, opposition-run institutions. Turkey’s state building efforts are dependent on the regime’s enemies — and the regime is allied with Iran and Russia. The YPG, too, has deftly managed relations with the various external actors in Syria and now has an American security guarantee east of the Euphrates.

And this is the bigger issue for the U.S.-Turkish relations. Washington has two main military goals, now that ISIL has been territorially defeated: First, hunt down and kill ISIL leaders and hold the territory taken, and second, use the SDF as a bulwark against Iranian expansionism. This approach requires working through local partners — namely the SDF. As long as this is the U.S. policy, tensions with Turkey will remain. In parallel, Ankara’s anti-American rhetoric and authoritarian turn have only deepened American hostility towards its NATO ally. The same is true in Turkey, which views the U.S. support for SDF as a direct security threat.

The “Border Security Force” kerfuffle is a manifestation of U.S. – Turkish disagreement. The two sides will not be able to repair relations in the near term. A Turkish invasion of Afrin may only harden U.S. resolve to stay in Syria. If a quadripartite anti-American collation does take shape, the instinct, again, will be to protect military gains. A U.S. presence will irritate Turkey, exacerbating the current drivers of tension.

Aaron Stein is resident senior fellow at the Atlantic Council’s Rafik Hariri Center for the Middle East.

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