The Turkish military announced Monday that Turkish soldiers, accompanied by American counterparts, began “independent patrols” in Manbij, Syrian Kurdistan, where Ankara spent months threatening an invasion against local Kurdish forces.

The Syrian Kurdish People’s Protection Units (YPG), the main militia within the Syrian Defense Forces (SDF) umbrella group, reportedly left Manbij after coming to an agreement with their American allies in early June. The YPG is considered one of America’s closest allies in the war against the Islamic State. Turkey considers the YPG a terrorist group, indistinguishable from the U.S.-designated Marxist terrorist group Kurdistan Workers’ Party (PKK).

Independent human rights groups and Kurdish activists have accused Turkish-backed Arab Syrian groups of confiscating and stealing Kurdish land and property in northern Syria, which Kurds call Rojava. Turkey’s presence in the region has also infuriated Damascus, where Bashar al-Assad’s regime has called for a full withdrawal of Turkish “invading” troops from Syrian land.

The Turks insist that they have legitimate security interests in eliminating the YPG. The Pentagon has defended their claims against the Kurds despite YPG contributions to multiple Islamic State defeats, including in their former capital, Raqqa.

The Turkish military announced the operation in conjunction with U.S. troops on Twitter, stating, “As per the Manbij Roadmap and Safety Principles previously agreed upon, independent patrol activities by soldiers of Turkish Armed Forces and U.S. Armed Forces have begun on the line between (the Turkish-controlled) area and Manbij.”

Turkish government spokesman Bekir Bozdag told reporters Tuesday that Washington and Ankara agreed to a three-month timetable for removing Kurdish elements from Manbij.

“While a joint work is carried out to liberate the area from the terrorists, simultaneous efforts for the administration and the security of the region are being addressed and solved,” Bozdag said. He emphasized that Turkey would hand over Manbij to “the local people,” though the YPG Kurds are indigenous to that area.

The Manbij Military Council (MMC), a local militia, denied that the Turkish joint patrols had begun within Manbij city limits on Monday.

“Turkish Army has not entered Manbij, they are only inside Sajur border line and they have begun mobilization inside Euphrates Shield borders,” Mohammed Abu Adil, an MMC commander, told the Kurdish outlet Rudaw. “We will say it clearly: No Turkish forces have entered Manbij, neither its villages nor the town itself.”

Last week, Human Rights Watch (HRW) accused Turkish-allied Free Syrian Army (FSA) fighters of stealing Kurdish property throughout Afrin, a Kurdish region west of Manbij, “install[ing] fighters and their families in residents’ homes and destroy[ing] and loot[ing] civilian properties without compensating the owners.”

An earlier report in the Guardian made similar accusations that “conquering Turks and their Arab proxies [have] swept in [formerly Kurdish-held Afrin], exiling nearly all its residents” and engaging in an ethnic cleansing of the region from Kurdish to Arabic.

The Afrin invasion has triggered similar concerns in Manbij. Unlike Afrin, however, Manbij has long been a U.S. base and American troops are reportedly involved in the transition handing the region over to Turkey. Early this month, the U.S. said that it had reached an agreement to “reduce tensions” in Manbij by removing the YPG. A YPG statement confirmed the deal, saying that YPG fighters had not been in Manbij since November 2016 but that it would withdraw advisers working with the local Manbij Military Council militia.

Shortly after that announcement, several reports indicated that the SDF group had begun reaching out to the Assad regime, as well as its Iranian and Russian allies, to strike a deal to curb Turkish influence in the country.

“We don’t have any other option. So, this is our land, it’s our right, and it’s our duty to liberate it, and the Americans should leave, somehow they’re going to leave,” Aldar Khalil, the co-chair of the largely Kurdish Movement for a Democratic Society, said at the time.

The joint patrols announced this week have infuriated the Assad regime in Damascus.

“The Syrian Arab Republic expresses its strong condemnation and absolute rejection of the incursion of Turkish and US troops in the vicinity of the city of Manbij, which comes in the context of the continued Turkish and US aggression against the Syrian sovereignty and territorial integrity,” an official said in a report by the state-run Syrian Arab News Agency (SANA).

The announcement of joint patrols followed remarks by Pentagon chief Jim Mattis last week in support for the SDF, but not the YPG.

“The SDF was the only organization that was able to throw ISIS off track and defeat them in the field in very, very tough fighting,” he said, according to the Washington Times. “We will not simply cast that organization aside, because it is critical to defeating the ISIS caliphate and preventing the rise of ISIS 2.0.”

Mattis went on to call northern Syria “the most complex battle space I have seen.”

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