The jihadist takeover of Syria's key Idlib province raises the prospect that the region could become the next target of the international participants in the country's complex war.
The northern province is one of only two that have fallen from regime control since the war began in March 2011 with anti-government protests.
Why is Idlib important?
Idlib is the only province in Syria that remains entirely beyond regime control after having been captured in 2015 by an alliance of jihadists and rebels named the Army of Conquest.
It borders Turkey and includes the key Bab al-Hawa border crossing, but also sits alongside Latakia province, a stronghold of President Bashar al-Assad's government.
The alliance that captured the province was dominated by Al-Qaeda affiliate Al-Nusra Front and the rebel Ahrar al-Sham, a key Islamist faction backed by neighbouring Turkey and Gulf states.
In the years since the capture, Al-Nusra ostensibly split with Al-Qaeda, renaming itself Fateh al-Sham Front and becoming the backbone of the so-called Hayat Tahrir al-Sham (HTS) coalition.
Despite their one-time alliance, tensions have been growing for months between HTS and non-jihadist forces in the province.
These have been exacerbated by fears inside HTS, designated a "terror" group internationally, of a plan to push it from Idlib.
How did jihadists seize it?
On Sunday, HTS took control of Idlib city, the provincial capital, after its rivals withdrew.
The shock capture followed a truce after days of fighting between the jihadist faction and Ahrar al-Sham.
But it remains unclear if the truce deal officially handed over the city and large stretches of the province elsewhere to HTS.
Better organised and better armed than its rivals, HTS now controls "more than 70 percent" of Idlib province, according to the Syrian Observatory for Human Rights, a Britain-based monitor.
What does this mean for rebels?
Ahrar al-Sham's control is now confined to just a few dozen towns, areas and villages in southern Idlib, a major downgrade of its influence.
"It's pretty debatable whether Ahrar al-Sham even exists any more and it looks like what is left of it is being digested slowly in the stomach acids" of HTS, said Syria analyst Sam Heller of the Century Foundation think tank.
The faction's subjugation comes after a string of major setbacks for Syria's non-jihadist opposition, who have lost large swathes of territory since Russia intervened to bolster Assad's regime in 2015.
"The geographic and political heart of the opposition at this point is in the northwest, and the northwest at this point has just been pretty decisively taken over by this latter iteration of Al-Qaeda," said Heller.
Elsewhere, two other key rebel areas in the south and outside the capital Damascus are now under internationally brokered truce agreements being monitored in part by Russia.
What next for Idlib?
HTS is designated a "terrorist" group by the United Nations, United States, Russia and Turkey.
It is regarded as a jihadist threat second only to the Islamic State group, which is currently facing multiple offensives with international involvement.
Since 2015, Russia has urged opposition supporters to force rebels to part ways with HTS and unite in a fight against jihadists in Syria.
With the lines now clearly drawn on the ground between the former allies, Idlib province could become the next target of an anti-jihadist offensive.
Rumours have circulated for months about a potential Turkish or even Russian attack against HTS in the province.
Analyst Nawar Oliver of the Turkey-based Omran Centre think tank said he did not expect a "major military operation" on Idlib.
"We may see an escalation of coalition air strikes on some HTS positions," he said, referring to the US-led coalition that is currently focused mostly on fighting IS in Syria and Iraq.
He said regime ally Russia could also step up its air strikes.
"But the regime will not be able to mount a ground attack now because it is fighting on many fronts. It cannot open a new front right now."
On Monday, activists expressed fears about the possibility of fresh heavy air strikes on the province and the prospect of civilian casualties.
And many civilians on the ground also fear a total jihadist takeover of the province.
During the clashes between HTS and Ahrar al-Sham, the jihadists twice opened fire on demonstrations against their presence, killing one protester.
