Syrian rebels and activists are warning that an Al Qaeda-linked jihadi group is on the verge of snuffing out what remains of the country's uprising in northwestern Syria, after the extremists seized control of the opposition-held regional capital, Idlib, last weekend.
With the jihadis cementing their authority over the city and its province, also called Idlib, Syrian president Bashar Al Assad has been supplied with a useful pretext for a long-expected assault against the rebellious province: that the uprising against him is largely driven by Islamists and terrorists.
"There is the real possibility that because of [Jabhat Al] Nusra's domination, the regime will enter the area with international approval," said Lt Col Fares Bayoush, a longtime opponent of Mr Assad, who has been leading a rebel faction in north Syria.
Jabhat Al Nusra is one of the many names for the Al Qaeda-affiliate that now heads the mighty Hayat Tahrir Al Sham militant group — Arabic for Levant Liberation Committee — that seized the city of Idlib, as well as two border crossings with Turkey to feed its coffers.
In July last year, Jabhat Al Nusra changed its name to Jabhat Fatah Al Sham and said it was cutting all its links with Al Qaeda, a move seen by many as an attempt to improve its image and market itself as a faction defending the Syrian people.
It abides by a deeply conservative code for ethics and jurisprudence and tolerates no dissent — leading many who live under its rule to complain they are no better than the government they sought to overthrow in 2011.
The fresh gains by Hayat Tahrir Al Sham in northern Syria come at a time when ISIL is suffering defeats at the hands of Iraqi and Syrian forces as well as US-backed Kurdish-led fighters in northern Syria.
In Idlib demonstrations last week, the group's members shot at protesters waving the tri-colour flag of the Syrian uprising. Hayat Tahrir Al Sham will only accept their own, jihadi-inspired black flags to be flown in their presence.
"Any party that tries to confront Hayat Tahrir Al Sham will be crushed," said an activist based in northwest Syria.
"This is a big blow for the Syrian revolution. Bashar will look like he is fighting terrorism," the activist said, speaking on condition of anonymity for fear of reprisals by the Hayat Tahrir Al Sham.
With its previous incarnations, Hayat Tahrir Al Sham has long been the top dog in Idlib province but the putsch has had the effect of making it feel official. In recent weeks, the group deployed masked gunmen and carried out raids in search operations for alleged ISIL members.
Hayat Tahrir Al Sham deployed across Idlib city last weekend after a rival faction, the ultraconservative Ahrar Al Sham group, withdrew. Five days of clashes around the province left 77 fighters and 15 civilians dead, according to the Britain-based Syrian Observatory for Human Rights monitoring group.
Other factions, including many once financed and armed in part by the CIA, kept to the sidelines. They are hoping to win a share of the revenues from the lucrative Bab Al Hawa border crossing, said a Turkey-based opposition activist who liaises with Syrian rebels and their state sponsors. He asked for anonymity so as not to jeopardise his position.
That crossing used to bring Ahrar Al Sham over $1 million (Dh3.67m) in revenues a month, according to a senior Ahrar Al Sham official, who also asked for anonymity for the same reason. The group will now have to share those revenues with Hayat Tahrir Al Sham after forfeiting its monopoly over it to a "civilian administration" forced in by the extremists.
Hayat Tahrir Al Sham also seized Sarmada — the first town after the Bab Al Hawa crossing and an important trade hub in north Idlib — and Khirbet Al Jouz, home to a second, less important crossing with Turkey.
"Ahrar Al Sham no longer has a real on-the-ground presence in Idlib province. It's over," said the Observatory's chief, Rami Abdurrahman.
Hayat Tahrir Al Sham and Ahrar Al Sham have long been at odds over Idlib, but the rout last week nevertheless carried a hint of betrayal, as the two sides fought side by side in 2015 to throw the government out of the province once and for all. Armed with anti-tank missiles supplied to supporting moderate opposition forces, some of which ended up in the hands of Jabhat Al Nusra, the coalition's advantage was so great that Mr Assad conceded, for the first time in the war, that he might not be able to retain control over all of Syria.
But Russia intervened with a bruising aerial campaign that drove the rebels and insurgents back on all fronts. Further infighting between the factions has all but doomed any hopes of rebels reaching the Syrian capital, Damascus.
Mr Assad, who has long eyed Idlib province since he lost it, will be further emboldened by a White House decision to halt the CIA supply-and-equip programme for Syrian rebels. It was first reported by the Washington Post last week.
Opposition activists saw it as an acknowledgement that Hayat Tahrir Al Sham was exploiting its position in northwestern Syria to pilfer weapons from vetted opposition groups.
"It means Hayat Tahrir Al Sham will have less access to arms," said the Turkey-based opposition activist.
But it is also a sign of growing closeness between the White House and the Kremlin over Syria.
Russia, a strong backer of Mr Assad, had long pushed the US to end the programme. And US secretary of state Rex Tillerson was reported to have told UN secretary general Antonio Guterres earlier this month that the US was leaving "Syria's fate in Russia's hands now", according to Foreign Policy magazine.