A powerful coalition of moderate Syrian rebel groups who receive covert backing from the West have renewed calls for a no-fly zone in the south of the country, as their offensive against government troops grinds to a crawl amid heavy bombardment.
The Southern Front is the largest force still to fight under the banner of the Free Syrian Army, and the dominant rebel formation in the city of Daraa, next to the Jordanian border. That places it within striking distance of the Syrian capital of Damascus.
The coalition is avowedly moderate and has publicly rejected coordination with Islamist militias, including al Qaeda's Syrian affiliate, al Nusra.
More appealing still to Western observers, they have been winning. From late 2014 until early summer this year, they notched up a string of impressive victories, beating back forces loyal to President Bashar al-Assad.
In one early success, they took the hilltop stronghold of Tal al-Harra last October, overrunning an abandoned Russian intelligence base. An Assad-regime general who had made contact with the Southern Front purposely deployed his troops in a weak formation, before defecting in a fake ambush, designed to make it look like he had been killed. He was spirited to Amman, where he provided vital intelligence, leading to the capture of the base, according to the National newspaper.
The victory pointed to another of the Southern Front's assets: their relative moderation make them an attractive target for defectors from the Assad regime who would never consider supporting Islamists.
By this summer, analysts were feting the Southern Front. One called them Syria's "last, best hope." But then the offensive stalled.
"We faced a very strong defense from the regime because of the symbolic and strategic importance of the city," Southern Front spokesperson Issam al-Rayes told VICE News. "Daraa is 50 miles from the capital and was where the revolution began."
"As we started the operation the regime started heavily shelling the civilians in surrounding villages with barrel bombs and also targeted field hospitals as a collective punishment method," he added. " It was hard for us to continue with this brutal onslaught."
Between late June and early September, the Southern Front took just a few blocks inside Daraa city.
A VICE News film released last week follows one of the brigades that make up the Southern Front during this hard-fought battle. The film tells the story of Zakaria Aboud, the brigade's commander, who before the revolution was a plumber, and his fight to take the eastern suburbs of Daraa.
The documentary shows the punishing impact of air attacks and heavy artillery on a force with no air force of its own, and on the surrounding civilian population.
Watch the VICE News documentary The Battle For Syria's South:
Rayes renewed calls for the international community to impose a no-fly zone over southern Syria, and said that the Southern Front would welcome ground-support airstrikes, similar to those which have been used to back the Kurds against Islamic State (IS) militants in the north.
"ISIS is the symptom of a cause, the cause is Assad," he said, using an alternative acronym for IS. "Dealing with the symptom without addressing the cause will not succeed and will be a waste of money as well as a waste of our blood."
"A no-fly zone will save civilian lives and will strengthen moderate opposition forces to address the cause of the problem: Assad. This is the way the west should be thinking about it, not the other way round," Rayes added.
But given that politicians in Britain and the US have ruled out direct intervention against the Assad regime, preferring to focus on IS, those calls are likely to go unheeded for now.
British Foreign Secretary Philip Hammond last week set out proposals to target only IS and said that he wanted to avoid becoming involved in "involved in complex three-way fights in north-west Syria where regime forces and other forces are involved," although the Southern Front itself fights only the regime.
Meanwhile, Britain and the US, along with several other allies in the region, are covertly involved in supporting the Southern Front through a Military Operations Centre (MOC) in Amman, it has been widely reported.
"Most sources report that each country that provides aid to the insurgency is represented in the MOC, but that major decisions are made by the United States, Jordan, and Gulf Arab countries supporting the insurgents," said Faysal Itani, a resident fellow with the Atlantic Council's Rafik Hariri Center for the Middle East.
"This support ranges from financial support, the provision of small arms and ammunition, strategic and tactical planning and advice, and the provision of resources to support aid provision and local governance in southern Syria."
This foreign backing was important in bringing together several rebel groups in 2014 to form the Southern Front.
Since that time, observers have welcomed the rebels' success, while expressing caution over their exact relationship with jihadist organizations such the Nusra Front and more moderate Islamists including as Ahrar al-Sham, as well as their real strength relative to such groups.
Because Jordan has closed its northern border to Syria to all but Syrians — a measure that has kept foreign fighters out, ensuring that IS is virtually non-existent in the area — journalists have been unable to enter, and independent verification of the situation on the ground has been hard to come by.
"These groups are not welcome in our operations rooms," Rayes said, referring to the Nusra Front and Ahrar al-Sham. "They do not share our ideology and our vision for a democratic, pluralistic, free Syria."
Itani said that nonetheless there is a sense in which they coordinate.
"If you mean one knows what the other is doing, and that there are efforts at promoting a synergy at times during battles and in choosing battles, this does exist," he said. "The MOC knows it does, and understands it would be unrealistic to expect otherwise. I would distinguish this from cooperation, as in launching joint operations or fighting side by side."
"Nusra provides essential shock troops and, critically, suicide bombers. Relative to its numbers, it has disproportionate importance," he added.
In what may be a sign of their relative influence, a local court contains eight delegates from the Southern Front and four from Nusra, according to Marika Sosnowski, a legal commentator.
In the past, internal debates within the Southern Front over relations with Islamists have focused on the military implications of rejecting them.
As such, one motive foreign governments have for providing support through the MOC is to give them the leverage to encourage a relatively moderate orientation within the Southern Front, and make them less reliant upon alliances with Islamists.
The reason more conservative variants of jihadist Islamism have failed to gain a grip in southern Syria compared to the north is partly because Jordan has hosted the MOC and kept a tight grip on the border.
In contrast, Turkey has long been criticized for its relations with Islamist groups — even having been accused of links to IS — and for allowing foreign fighters to slip undeterred across its southern border.
Fighters in southern Syria are more likely to be local, and links of tribe and clan are strong, binding armed groups into the social fabric, and encouraging regard for civilian opinion, according to Itani.
Follow Tom Dale on Twitter: @tom_d_