Not all of the United States' coalition allies share its desire to start targeting Raqqa in the next few weeks. For the most part, their dissent stems from the city's composition: Raqqa is predominantly Arab, which means a sizable Arab force would be needed to seize and hold it. Though the Western-backed Syrian Democratic Forces include several Arab units, the Kurdish People's Protection Units (YPG) continue to make up an overwhelming share of the group.
In an effort to remedy this problem, the United States deployed 250 special operations forces to Syria in April to speed up the recruitment and training of Arab fighters ahead of the push for Raqqa. According to the congressional testimony of U.S. Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford, the Syrian Democratic Forces had about 6,000 Arab fighters (20 percent of the force) at the time. By September, Dunford had updated his statement to say that 14,000 Arab fighters had been identified, though he did not say how many had joined the Syrian Democratic Forces or had been trained. (Notably, he added that the United States has a plan to hold Raqqa once it is captured but that the plan had yet to be resourced.) Nevertheless, Turkey and several NATO member states remain unconvinced that enough Arab forces have joined the coalition.
Even the United States has had to admit that the Kurdish YPG — still the largest component of the Syrian Democratic Forces — will, by necessity, play a decisive role in the operation to retake Raqqa. Yet that will pose a significant risk in itself, raising the possibility of inflaming the country's deeply rooted sectarian tensions. This danger has alarmed several U.S. partners, including the United Kingdom, and British Defense Secretary Michael Fallon has warned that Raqqa's Arab population may not welcome a Kurdish invasion.
The ally that could most impede Washington's plans, however, is Turkey. Ankara not only shares London's concerns of rivalries emerging between Arabs and Kurds, but it also holds great hostility toward the Kurdish YPG. Turkey, anxious to avoid relying on or strengthening the Kurds, has instead proposed an alternative: Postpone the Raqqa operation until the coalition gains enough Arab fighters to replace the YPG in the offensive. Turkey has even begun to train Arab fighters on its own side of the Syrian border, and it has promised to actively participate in the operation if the Kurds are excluded from it.
But Ankara's plan would not be put into practice fast enough for Washington's liking. The United States wants to start the Raqqa operation immediately, and since the Syrian Democratic Forces are the only group ready to do so, the United States appears to be intent on placing the offensive on their shoulders. Turkey's opposition could be problematic, though. Syria's Turkish-backed rebels are already clashing with Kurdish YPG units in northern Aleppo; further conflict, or perhaps a rebel push toward Manbij, could easily distract the Kurds from the Raqqa operation down the road.
Aware of these risks, the United States has had little choice but to lower its expectations. Though a Raqqa operation will probably still begin in the coming weeks, it will open with an isolation phase instead of a direct assault on the city. This approach will restrict the Islamic State's movements while avoiding the bigger gamble of driving straight into the heart of Raqqa until more Arab fighters can be found. Meanwhile, the United States will decide whether to boost the number of U.S. special operations forces in Syria. Should Washington send hundreds of additional troops, they would likely focus their efforts on managing the coalition's shaky structure in northern Syria. The troops would essentially act as the glue holding the coalition together, facilitating communication among its participants and deconflicting operations. Their presence would become all the more critical if Turkey elects to send its own force toward Raqqa, though Ankara has adamantly refused to participate in the operation alongside the Kurdish YPG. In the end, the United States may yet come up with a compromise — as it has in the Mosul offensive — whereby the Kurds help to surround Raqqa while Turkey's allies and other Arab fighters spearhead the capture of the city itself.