The U.S.-led coalition's fight against ISIS in Syria is in jeopardy as Turkey threatens an offensive against the U.S.'s primary partner force on the ground, the Syrian Democratic Forces. Turkey has stated its intent to shift its focus from ISIS to the Syrian Kurds after the seizure of the ISIS-held town of al Bab in Northern Aleppo Province, which ISW forecasts is likely in the coming weeks. If the U.S. fails to protect its partner force, the Syrian Kurdish-led de facto government of Northern Syria may pursue closer cooperation with Russia, which could hinder the U.S.'s ability to influence the outcome of the Syrian Civil War and continue its operations in the country. Conflict between the U.S.'s allies in Northern Syria will also relieve pressure on ISIS in Raqqa Province and thereby allow ISIS to seize territory from the Syrian regime or reinforce its core terrain in Iraq.
Turkey's threat to launch an offensive against the Syrian Democratic Forces (SDF) after the impending seizure of al Bab endangers the U.S.-led coalition's fight against ISIS in Syria. Turkish Armed Forces (TSK) and Turkish-backed opposition groups entered the ISIS-held town of al Bab in Northern Aleppo Province on February 9 following a two and a half month offensive on the town. Pro-regime forces severed ISIS's last remaining ground line of communication south of al Bab on February 6, and ISW forecasts that the city will likely fall in the coming weeks. Turkish President Recep Erdogan stated on January 27 that the Turkish Armed Forces and Turkish-backed opposition groups will not advance further south following the seizure of al Bab, but rather will launch an offensive against the SDF in Manbij City to push the SDF east of the Euphrates. The U.S. is relying on the SDF as the only U.S.-led coalition partner force currently capable of isolating ISIS's de-facto capital in Syria - ar-Raqqah City. A Turkish offensive that both distracts and weakens the U.S.'s partner force in Syria will diminish the U.S.'s ability to combat ISIS in Syria.
Turkish officials have consistently announced their hostility towards the dominant group in the political alliance behind the SDF, the Syrian-Kurdish Democratic Union Party (PYD), due to its links to the Kurdistan Workers' Party (PKK), a U.S.-designated terrorist organization. Turkey launched Operation Euphrates Shield, currently a TSK and Turkish-backed opposition offensive against ISIS in Northern Aleppo Province, in large part to prevent the formation of a contiguous zone of control along the Syrian-Turkish border de facto governed by the PYD. In addition, TSK and Turkish-backed forces recently increased attacks against the SDF in Northern Aleppo Province, indicating that Turkey is preparing to escalate its currently low-scale conflict with the SDF. Turkey is also using arrests of alleged 'PYD militants' in Turkish-held Northern Aleppo Province and Turkey to reinforce Turkey's designation of the PYD as a terrorist organization and legitimize their potential offensive.
Turkish President Recep Erdogan is likely timing its assault on the SDF in Northern Aleppo Province in conjunction with preparations to hold a referendum on a constitutional amendment package that would increase his executive powers. A Turkish offensive on the SDF will demonstrate Erdogan's commitment to Turkey's ongoing anti-PKK campaign, which is likely to increase popular support for the proposed constitutional amendments. Turkish officials likely also see U.S. President Donald Trump's reported rejection of previous plans to increase support for the SDF as well as his recent phone conversation with Erdogan as indicators that the new administration is open to sacrificing support for the SDF in exchange for a closer partnership with Turkey in Syria.
A Turkish offensive to drive the SDF east could divert Turkish and SDF resources from combatting ISIS for months. The U.S. will likely attempt to hedge this effect by offering Turkey a leading role in operations to seize ar-Raqqah City. A Turkish offensive would require SDF approval to traverse Kurdish-held terrain, however, otherwise Turkish forces would have to advance approximately 100 miles through ISIS-held territory before attacking ar-Raqqah City. The PYD is opposed to allowing Turkey to establish a governing structure in ar-Raqqah City that is hostile to its goal of establishing a federal system in post-war Syria. The PYD is currently creating local governance structures for the city and the surrounding region with the support of local Arab tribal leaders in order to demonstrate the viability of its proposed governance structure and establish allied control over the region. Moreover, the extended Turkish assault on the ISIS-held town of al Bab demonstrates that Turkish-backed opposition forces are not independently combat capable of seizing ISIS-held urban terrain. A successful Turkish assault on ar-Raqqah City would require an increased commitment of TSK troops or the use of prominent Salafi-jihadi group Ahrar al Sham in addition to the full support of the U.S.-led coalition. Most dangerously, a halt to the SDF's operations against ISIS could allow the group to retake territory in Northern Syria, divert forces to its assault on pro-regime held Deir ez-Zour City, or send reinforcements to defend Mosul City in Iraq.
The PYD may turn to Russia as an alternate patron if the U.S. fails to prevent an offensive against the SDF or attempt to allow Turkey a greater role in the ar-Raqqah offensive. Russia has attempted to reconcile the PYD with its rival Syrian-Kurdish political parties in the Kurdish National Council and the Syrian regime in the past. Russia is also hosting a pan-Kurdistan meeting in Moscow on February 15 to reportedly discuss ways to foster Kurdish unity and PYD requirements for a post-war Syrian constitution. The PYD has already allowed Russian military police to patrol its controlled districts within Aleppo City and currently shares territory with pro-regime forces in Northern Aleppo Province west of the town of al Bab. The regime also reportedly delivered twenty-five tons of ammunition to the SDF on October 13 before the SDF launched operations against ISIS in ar-Raqqah City. Russian mediated reconciliation between the regime and the PYD would be a major political coup against U.S. influence in Syria, effectively pushing the U.S. further out into the fringes of being able to affect both the Syrian Civil War and the fight against ISIS in Syria.
Turkey may indicate an upcoming offensive by deploying further TSK reinforcements to the towns of Jarablus and Azaz in Northern Aleppo Province. An escalation in clashes between Turkish-backed opposition groups and the SDF in Northern Aleppo Province will also indicate that Turkey is shifting the focus of its operations in Syria from ISIS to the SDF. Syrian Kurds could show signs of drifting to Russia's sphere of influence by accepting Russia's offered concessions in a potential post-war Syrian constitution or taking increasingly frequent meetings with Russian officials.