KARKAMIS, Turkey — Turkey’s incursion into Syria is deepening tensions between two major U.S.-backed groups, potentially setting up a conflict that could undermine Washington’s efforts to eradicate the Islamic State’s presence in Syria.
A focal point of those animosities is the strategic Syrian town of Manbij, nestled on the western side of the Euphrates River. The Kurds wrested it from the Islamic State this month. Turkey and the Syrian rebels it supports fear that the takeover is a prelude to the Kurds expanding their reach further in Syria. On Thursday, under U.S. pressure, the Kurdish forces, known by the acronym YPG, declared that they had pulled out of the predominantly Arab town.
The announcement came hours after Turkish tanks and special forces units, backed by U.S. and Turkish fighter jets, crossed the border and helped Syrian rebels to seize the city of Jarabulus from the Islamic State.
But in interviews Friday, Syrian Arab and ethnic Turkmen rebels backed by the United States and Turkey said the Kurds were still in control of Manbij, and they vowed to liberate it. The Turkish military has bombed targets around the town, 25 miles south of Jarabulus, apparently convinced that the Kurds have not followed through on their promise to leave or that they seek to return.
"Our concern has been the fact that the YPG has a proven track record of forcibly displacing non-Kurds," a senior Turkish official said, speaking on the condition of anonymity as per protocol.
On Saturday, Turkey said it launched more airstrikes against Kurdish forces north of Manbij, while U.S. and Turkey-backed Syrian rebels battled fighters aligned with the Kurds near Jarabulus. By nightfall, tensions had ratcheted up. Turkey's state-run Anadolu Agency reported that a Kurdish rocket struck two Turkish tanks, killing a soldier and injuring three others south of Jarabulus, marking Turkey’s first casualties in the offensive and, potentially, a widening of the war.
The animosities threaten to pit two groups of U.S.-aided forces — the CIA- and Pentagon-backed Syrian Arab and Turkmen rebels and the Pentagon-backed Kurdish forces — against one another, potentially taking their attention away from fighting the Islamic State, also known as ISIS or ISIL. It also illustrates the challenges the United States faces in coordinating this array of armed groups, beset by ethnic and territorial rivalries as well as different agendas, on an increasingly complex, multisided battlefield.
To be sure, Syrian rebels and Kurdish forces have regularly fought one another elsewhere in Syria. But they have both been battling the Islamic State, albeit on separate fronts. Now their conflict could expand into new areas, as Turkey’s incursion transforms Syria’s military landscape.
The Syrian Observatory for Human Rights, a well-known Britain-based activist group, said that Kurdish forces and Syrian rebels engaged in skirmishes Wednesday night around several villages between Jarabulus and Manbij. On Saturday, Turkish warplanes struck the Kurdish targets near the village of Al-Amarna, five miles south of Jarabulus, as Syrian rebels clashed with fighters of the Jarabulus Military Council, which was recently set up by the Kurdish forces.
Many observers say Manbij could once again become a front line.
“We are still waiting to see if they are going to retreat back to east of the Euphrates,” said Ahmed Othman, the commander of an ethnic Turkmen force within the U.S.-supported Free Syrian Army, referring to the Kurds. “If not, we will have to push them back by force.”
The Kurds say they handed over their positions to a local military council in Manbij made up largely of Arabs. But the body is perceived by the Syrian rebels to be controlled by the Kurdish forces. On Friday, the Kurdish spokesman for the council said it would confront any Turkish-backed rebels entering their town.
“We will defend ourselves,” said Shervan Derwish, who has also served as the spokesman for Kurdish forces who fought off Islamic State combatants in a famous battle in the Syrian town of Kobane last year. “Those guys are here to serve Turkey’s agenda, not the Syrian revolution’s goals.”
Nizar Mehdi, a journalist and activist from Manbij, said relatives and friends in the town told him that Kurdish forces were still in the area and operating from bases.
A U.S. defense official, speaking on the condition of anonymity because he was not authorized to comment on the record, said that while Kurdish commanders and most of their fighters had withdrawn to the east of the Euphrates, a smaller number of Kurdish forces remain within Manbij. They are combing the city, he said, for explosives left by the Islamic State and seeking to ensure that militants do not return.
“They fought very long and hard to take the city, and we want to make sure there’s a ‘hold force’ in place to make sure that ISIL doesn’t reinfiltrate,” the official said.
The official acknowledged that there had been tension between Kurdish and Arab fighters in the area but played down its significance. “This is a pretty standard feature of coalition warfare,” he said. He said the United States was working to defuse friction in part by “reminding everyone of who the real problem is here, which is ISIL.”
This year the Pentagon added about 250 Special Operations forces to bolster a smaller force already in northeastern Syria. U.S. officials said their principal mission was to oversee the recruitment and training of more Arabs for the fight against the Islamic State, apparently to help make the Kurds not appear as an invading force. But U.S. Special Forces have also been accompanying Kurdish fighters on some of the front lines, including during the battle for Manbij.
The Pentagon’s backing of these forces — collectively called the Syrian Democratic Forces and dominated by the YPG, which in Kurdish stands for People’s Protection Units — has irritated Turkey. Tensions have increased as Kurdish forces expanded their areas of control in Syria in recent months, moving closer to zones controlled by rebels backed by the United States and Ankara, Turkey’s capital.
Many observers say one of Turkey’s main objectives in the offensive, code-named “Euphrates Shield,” is to stop the Kurds from gaining territory in Syria. The Turkish government has long confronted a restive Kurdish minority within its borders, and it sees efforts by Kurds in nearby countries to increase their reach as a security threat. The Syrian Kurdish rebels have ties to the Kurdistan Workers’ Party, or PKK, which fought a bloody war against the Turkish military for decades.
In the past, Turkey has considered creating a buffer zone that would allow the Syrian opposition to better fight Syrian President Bashar al-Assad’s regime as well as the Islamic State. Such a zone would also lead to the creation of a safe area that could allow more than 2 million Syrian refugees in Turkey to return home. Whether this is a goal of the current offensive remains unknown.
What is clear, though, is that Ankara seeks to block Kurdish aspirations to unify two Kurdish-controlled enclaves along Turkey’s border in northern Syria, which Turkey fears could also embolden the PKK inside its soil.
On Friday, Turkish Prime Minister Binali Yildirim told reporters in Istanbul that Turkey “will continue operations [in Syria] until we fully guarantee security of life and property of our citizens and the security of our border.”
“We will continue until the Islamic State and other terrorist elements are taken out,” he said.
Other top officials have openly noted that Turkey’s objectives include curbing Kurdish territorial expansion in Syria.
Turkey’s defense minister, Fikri Isik, said the operation has two main goals, including securing the border and preventing Kurdish forces from reaching the area west of the Euphrates. “Our strategic priority is preventing [the Kurds] from joining their east and west cantons in Syria,” Isik said in an interview Thursday with Turkey’s NTV network.
Syrian rebels are continuing to secure Jarabulus as more Turkish tanks have rumbled over the border to assist them. Teams have been scouring neighborhoods for land mines and improvised explosive devices left behind by the Islamic State.
Others have been digging trenches, fortifying the city for any future attacks.
“We want to prevent any enemy advances, and by enemies we mean ISIS and the YPG,” said Abu Ibrahim, another Free Syrian Army commander, referring to the Kurds. “Everyone knows what ISIS is, but the YPG is trying to divide Syria, and that is also not acceptable.”
Missy Ryan in Washington, Zakaria Zakaria in Gaziantep, Turkey, and Liz Sly in Beirut contributed to this report.