The reason Erdogan cites for a potential new operation is to prevent “a terror corridor” in the area — a justification that has never changed since the YPG, which Ankara considers a terrorist group, seized Tell Abyad to secure a link between Kobani and Jazeera in 2015. In his remarks in New York , Erdogan reiterated the argument, saying that Turkey took control of Jarablus, al-Bab and Afrin to “not let [the region] become a terror corridor.” Referring to US support for the Kurds, he added, “Unfortunately, our strategic partners are taking different steps. Unfortunately, 18,000 trucks full of weapons and ammunition have been sent to this region, in addition to 3,000 cargo planes.”

Later, when Ankara sought to dissuade Washington from collaborating with the YPG in the liberation of Raqqa, its alternative plan involved 10,000 fighters from the Free Syrian Army marching on Raqqa with Turkish military support on a route from Tell Abyad via Ayn Issa to Raqqa. The plan was meant to halt US support for the Kurds, but also to allow the Turkish military to cut the connection between the Kobani and Jazeera cantons.

In Tell Abyad, the Arab population is relatively larger than the Kurds, while in Ras al-Ayn the two ethnic groups are roughly equal. In September 2012, Tell Abyad was seized by Jabhat al-Nusra, Ahrar al-Sham, the Tawhid Brigade and al-Furqan Brigades, but following a rift between the al-Qaeda-linked groups, it fell into the hands of the Islamic State in January 2014. When the YPG and its Arab allies ousted IS from Tell Abyad the following year, Turkey accused the Kurds of ethnic cleansing in Arab and Turkmen villages. A disputed report by Amnesty International included similar claims.

The first area in Turkish crosshairs appears to be Tell Abyad, which lies between the Kurdish-dominated Jazeera and Kobani cantons. Another relatively easy target for Turkey is Ras al-Ayn, a region to the east of Tell Abyad that was the scene of clashes between the Kurdish People’s Protection Units (YPG) and Syrian rebels sneaking via Turkey’s border town of Ceylanpinar after the Kurds took control of the area in July 2012.

Having struck a deal with Russia that deferred a regime offensive on Idlib, Turkish President Recep Tayyip Erdogan has again set his sights on Kurdish-controlled areas in northern Syria. In Sept. 23 speeches at gatherings organized by Turkish-American groups in New York, where he is attending the UN General Assembly summit, Erdogan raised the specter of a Turkish military intervention on the eastern side of the Euphrates River, where US-backed Kurds hold sway. “We will increase the number of secure zones inside Syria in the coming period, encompassing the east of the Euphrates,” he said in one speech. Then, referring to earlier Turkish operations in the region, he told another gathering that Turkey “will take steps similar to the Euphrates Shield and Olive Branch operations in the east of the Euphrates as well."

An intervention in Tell Abyad could be relatively easy to sell to the Turkish public, using the arguments of thwarting the terror corridor and securing the return of Arabs and Turkmens who have been subjected to ethnic cleansing.

Beyond the rhetoric, there is some military movement on the ground. Both Syrian Kurdish sources and Turkish media outlets close to the government have reported a military buildup in the Turkish border town of Akcakale, which is facing Tell Abyad. In its coverage of Erdogan’s remarks in New York, the Turkish daily Takvim reported, “Now that the Idlib issue is on a settlement course, Ankara’s attention has shifted back to the east of the Euphrates. The button has been pressed in this regard. Military units along the border have been reinforced. The initial intervention, we have learned, will target Tell Abyad, Kobani, Qamishli and Ras al-Ayn.” The Hawar news agency, meanwhile, reported the presence of hundreds of military vehicles and heavy weapons on the Turkish side of the border.

Salih Muslim, a prominent Syrian Kurd who until recently headed the political arm of the YPG, did not rule out a Turkish offensive. “Turkey is making a [military] buildup on the border. It wants to make some move, but the conjuncture is not favorable. Of course, it needs to get rid of [the issue of] Idlib first,” he told Al-Monitor. “We cannot say whether the United States will deter [Turkey]; you have to ask them. We rely on our own strength; no one has given us assurances of protection.”

How Erdogan’s pressure plays out will depend largely on Russia and the United States. Though Russia had greenlit Turkey’s march on Afrin, it is too early to speculate how it will view a Turkish move east of the Euphrates. Having said that, Russia’s two key reasons to facilitate things for Turkey in Afrin are still valid. The first is to ensure Turkey’s continued cooperation in the Astana framework. Second, the Turkish threat comes in handy for Russia in efforts to draw the Kurds away from the United States and force them into a compromise with Damascus. The only caveat for Russia here is that Turkey might become too involved in the equation, to an extent that would allow it to impose its demands. This is a reason for alarm in Damascus as well.

The lack of tangible progress in two rounds of talks between the Kurdish-led Syrian Democratic Council (SDC) and Damascus, coupled with Kurdish moves to extend the self-rule project to northeastern Syria, seems to be pushing Russia to take a more explicit position on the issue. In an important signal to that effect, Russian Foreign Minister Sergey Lavrov said Sept. 21, “The main threat to Syria’s territorial integrity comes from the eastern bank of the Euphrates, where independent and autonomous entities are being created under US control. We will insist this unlawful activity should be brought to an end.”

The Turkish service of Russia’s Sputnik network, meanwhile, reported that the American military presence in Syria had reached 25 bases and 5,000 troops. In remarks backing up the report, Gelo Isa, a senior SDC member, told Sputnik, “The United States is increasing its military presence in Syria. It is setting up new bases and expanding [existing ones]. The United States will stay long in Syria.”

The Americans are also present in the corridor that Turkey wants to dismantle, including in Deriq, Rmeilan, Kobani, Ayn Issa and Tell Abyad. In 2016, after seizing the area from Jarablus to al-Bab, Turkey had to put on the brakes at Manbij, its next target, under US pressure. After protracted negotiations, the United States acquiesced only to joint patrols with Turkey around Manbij and leaving the city to local forces.

Now Turkey is eyeing an even larger intervention. How the United States might agree to such a move remains a mystery, for it would require a major shift in its Syria policy. Without such a shift, Turkey’s intervention would amount to an intervention against the American presence as well. In a sharp message that Washington is not yet done in Syria, National Security Adviser John Bolton vowed Sept. 24 that US troops would not leave the country “as long as Iranian troops are outside Iranian borders.”

Still, it would be fair to predict that Erdogan will continue to insist on an intervention, looking to take advantage of US-Russian rifts and seize any opportunity that comes along by using vacuum-filling tactics. Keeping up the threat appears aimed at launching a new bargaining process with Washington at least. A Turkish move on Tell Abyad is unlikely without some sort of understanding or rapprochement with Washington, even if a tacit one. At present, the purpose of military reinforcement at the border appears unlikely to go beyond applying psychological pressure on the YPG, compelling Kurdish-friendly Arabs and Turkmens to change stance, promoting Turkish positions before the international public and demonstrating a general resolve.