Bashar al-Assad’s forces swept into cities across northeast Syria for the first time in seven years on Monday after the West’s former Kurdish allies agreed to a Russian-brokered deal to try to hold off a Turkish attack.
The Syrian regime’s black-and-red flag went up across the region as Russia seized on Donald Trump’s abandonment of the Kurds to restore Assad’s rule over swathes of territory he has not controlled since 2012.
Assad’s troops clashed with Turkish-backed Syrian rebels outside Manbij, a key city on the Turkey-Syria border where US forces are evacuating on Mr Trump’s orders.
Western officials are watching closely to see if the skirmishes escalate into a direct confrontation between Turkey and the Syrian regime, or whether Russia can broker another deal to keep the two countries from clashing.
Several European countries joined France and Germany in halting arms sales to Turkey, as the EU put out a joint statement condemning the offensive.
Fears were also rising over an Islamic State (Isil) resurgence as it emerged that US forces had failed to secure dozens of the most hardened jihadist fighters, and Isil prisoners once again rioted against their Kurdish guards.
Mr Trump suggested the Kurds were deliberately freeing Isil prisoners in a bid to get the West’s attention, a talking point that has been repeatedly used by Turkey’s government to discredit its Kurdish enemies.
Assad’s re-entry into northeastern Syria marks a dramatic redrawing of the lines of control in the war-torn country and likely signals the beginning of the end of seven years of Kurdish autonomy in the area.
Regime fighters began entering the provinces of Hasakah and Raqqa and were moving quickly to consolidate their control over long swathes of the Turkish-Syrian border with the permission of Kurdish troops.
The exact details of the agreement between Damascus and the Kurds remains unclear. Kurdish authorities insisted that they would maintain their political autonomy and that the deal was focused solely on military issues.
But other reports suggested that the Syrian Democratic Forces (SDF), the Western-backed Kurdish units who led the fight against Isil, would be folded into Assad’s army and that northeast Syria would come back under direct rule from Damascus.
The immediate focus of the newly-aligned SDF and Assad regime is to repel Turkish-backed rebels from seizing control of Manbij, a border city west of the Euphrates River which is currently in Kurdish hands.
The Syrian rebels, known as the National Army, said Monday night they had launched an operation to “liberate Manbij and its surroundings from the terrorist gangs”.
The National Army claimed to have engaged Assad’s forces and captured a tank in a first round of fighting.
The battle for Manbij will pose a test for Turkey, which must decide whether to back its Syrian rebel allies with airstrikes at the risk of sparking a confrontation with the Syrian regime.
Russia is believed to be relaying messages between the two sides to try to avert conflict.
Recep Tayyip Erdoğan, the Turkish president, said he was determined to put the city under the control “our Arabic brothers” in the National Army.
But while Turkish warplanes thundered overhead there were no reports they were striking Assad’s forces in support of the rebels.
US forces have been ordered to evacuate northern Syria but many troops remained caught up in the chaos as different armed groups maneuvered and the roads remained clogged with refugees.
The situation in northeast Syria collapsed into disorder so quickly that US special forces did not have time to carry out a plan to seize around 60 of the top Isil fighters in Kurdish custody, according to the New York Times.
US commandos had planned to take the prisoners from the Kurds and move them to Iraq but were unable to reach a key road in time.
It is not known if any British fighters were among the 60 men on the US list. America has already taken custody of Alexanda Kotey and El Shafee Elsheikh, the two surviving members of the “Beatles” group of alleged British executioners.
The report appeared to drastically undercut Mr Trump’s claim that “the US has the worst of the Isil prisoners”. Mr Trump also said the “Kurds may be releasing some [Isil prisoners] to get us involved” in trying to stop Turkey’s offensive.
Mr Erdoğan and other Turkish officials have made the same claim repeatedly in recent days. The Turkish military released a video which it claimed showed its commandos entering a Kurdish prison only to find that the guards had released all the inmates.
But Kurdish officials suggested the video was staged at an empty facility never used as a prison. SDF guards at a prison were wounded during a riot by Isil prisoners at Ain Issa, according to Kurdish media.
The Isil suspects still in Kurdish custody are panicked at the prospect they could be handed over to the Assad regime, which has a long history of torturing detainees.