The Kurdish-led Syrian Democratic Forces confirmed on Friday that its forces had entered the city of Deir ez-Zor, administered by the regime of Syrian President Bashar al-Assad. The Albu Kamal border crossing with Iraq — used by Iran-backed Shiite militias funneling men and weapons to their units in Syria — also fell under its control. The US-backed umbrella group said in a statement Friday that the Deir ez-Zor Military Council, staffed by mainly Arab forces, had moved into the city and into other areas lying on the western banks of the Euphrates River in order to protect its people from Turkish-backed Sunni militants who have been at war against the SDF as well as from the Islamic State.

The SDF took control over the city after Syrian government forces and Iran-backed fighters pulled out of the city, Reuters reported.

The moves are also likely aimed at giving the Syrian Kurds leverage over other actors in the conflict. They came as Hayat Tahrir al-Sham, the al-Qaeda offshoot that aligned with Turkey-backed groups in the so-called Syrian National Army, pressed its lightning offensive, now in its ninth day, against Syrian regime forces closing in on the country’s third largest city, Homs. The militant group has already captured Aleppo and Hama. The fall of Homs would bring HTS closer to its stated goal of overthrowing Assad’s regime.

The astonishing success of the group has created a vacuum in eastern Syria that the Kurds are rapidly filling in a replay of the pattern established at the start of the Syrian uprising in 2011, when regime forces retreated from Kurdish-majority areas to fight Sunni opposition rebels elsewhere.