Beirut, Lebanon - Hashem* says he locked the doors, drew the shutters, and hid in his house with his family. He feared being spotted by fighters from the former al-Qaeda-linked group, Hay'et Tahrir al-Sham (HTS), in Syria's Aleppo province.

"They came in and started shooting everywhere," said Hashem, a father of two in al-Atareb in Western Aleppo. "We are very, very afraid. They will kill us all."

HTS took over Hashem's town on Sunday as it continued its expansion campaign from Idlib - which it already dominates - into surrounding areas held by Turkey-backed groups of the National Liberation Front (NLF).

Over the past seven days, HTS captured several villages and at least one other town, Darat Izza.

The group's aim is to acquire more territory so it has a stronger hand to play as Russia and Turkey prepare a final political agreement over Syria's last rebel-held enclave, which sprawls across Idlib, parts of Aleppo, and a sliver of neighbouring Hama provinces.

Whatever settlement is reached will almost certainly demand the containment and elimination of the armed group.

Accused of crimes

According to the Sochi agreement, signed by Russia, Turkey and Iran last September, Ankara is already supposed to have started reining in the group. Instead, undeterred, HTS is making inroads into strategic areas such as Atareb.

The town is near Syria's main northwest highways, M4 and M5, which connect major cities within Syria and the country itself to her neighbour Turkey. Whoever controls these highways is likely to have a say in any end-game.

HTS has succeeded in becoming militarily the most powerful group in the enclave. However, it is opposed not only by all external forces with an interest in Syria but also by many ordinary residents.

It has been accused of executing members of moderate rebel groups, kidnapping civilians to extort money, and shutting down educational institutes, among other crimes.

Despite the lack of public support, HTS has managed to keep hold of large swaths of territory and exercised military superiority over the NLF, which has never been as coherent, organised - and fanatic - as HTS, as its component groups bicker over ideology and strategy.

60,000 lives at risk

The two local factions, Thawar al-Sham and Bayraq al-Islam, which ran Atareb alongside the larger Harakat Noureddin al-Zinki group, were routed out by HTS with ease and bussed to Afreen to the north.

Joshua Landis, director of the Centre for Middle East Studies at the University of Oklahoma, said the al-Qaeda-affiliated militia was stronger and better led, while Turkey-sponsored groups just "collapsed" and "fled in front of HTS's fighters".

"HTS's conquest of Atareb and Darat Izza dashes any notion that the National Liberation Front that was cobbled together by Turkey to act as a new Syrian national army is actually a cohesive or effective fighting force," Landis said.

The humiliating exit of rebel groups with which Hashem sympathised has placed the lives of 60,000 people in the town at risk, he said. Hashem is worried about HTS's ruthlessness as well as about the excuse their presence offers the Syrian government and the Russians to launch what many residents have long believed to be an impending attack.

Hashem said the Assad government would not stand by as HTS expanded and would act to eliminate it. But bombing HTS's fighters would also kill innocent civilians, he added.

"Now Russia and the regime can attack us because we are terrorists - but we are not terrorists," he said.

He added those who did not die in the offensive would be labelled traitors by the government and "either be killed or jailed", he said.

'Turkey will have to negotiate directly with HTS'

After Darat Izza fell to HTS, the town was bombed by Russian jets, according to residents, leaving three dead and nine injured in the first raids since the signing of the Sochi deal to keep the peace in wider Idlib.

Landis said this was the rationale Assad would use were he to violate the Sochi agreement.

"The Syrian authorities have argued that Turkey has not kept its side of the Idlib agreement," he said.

"Turkey had been promising both Russia and the West that its proxies could take care of HTS, but they cannot. Turkey will have to negotiate directly with HTS or face the growing possibility of a Syrian invasion of Idlib province."

Even Hashem is unable to understand why Turkey turned a deaf ear to the request of the local factions to send help.

"Our leaders reached out to Turkey, but they did not help," he said.

HTS timed its rampage well. In December, Turkey repeatedly planned and then called off an attack in Syria's northeast against the YPG, the Kurdish armed group it regards as a mortal enemy.

It has been left twisting and turning in response to a changing American policy towards the Syrian Kurdish fighters, who are tied to the PKK, the Turkey-based guerrilla organisation.

US President Donald Trump has promised to withdraw support as he seeks to withdraw American troops, but other US officials have given conflicting signals.

What will Turkey do?

Turkish President Recep Tayyip Erdogan may be more focused on his "Kurdish problem" than the intractable problem of dealing with HTS. Some analysts go so far as to suggest he did not want the NLF, whose brigades he is using to confront the Kurds, to lose men and concentration fighting HTS.

Others speculate Turkey and Russia may have reached an understanding that territories taken by HTS can be attacked and occupied by the Syrian army, in return for Russia allowing Turkey to do what it wants against the Kurds.

Aron Lund, a fellow with The Century Foundation, said Turkey might simply not be that concerned about armed group turf wars at this stage. He suggested Turkey also thought it could soften HTS' ideology to make it an acceptable partner - an easier option than taking it on militarily.

"I'm not sure how or if Turkey will respond to this, or if they're actually that concerned," he said. "Tahrir al-Sham is already in charge of most of the area, and Turkey seems to be working to soften them up and make them less problematic - rather than trying to overturn the entire situation."

Although the effect of the recent developments on the Sochi agreement is as yet uncertain, Lund said the outcome would depend on the "big-picture dynamics" of the Moscow-Ankara relationship.

"Tahrir al-Sham's expansion could trigger brutal fighting with the Syrian government, Russian bombings, some changes of territory, and lots of heated rhetoric and summitry," he said. "But that wouldn't necessarily kill the basic idea of the Sochi-Astana concept."

Hashem, scared to venture out in streets full of HTS fighters, said he doesn't understand the larger strategic calculations behind Turkey's failure to help the rebels, or why armed groups are being deployed to fight the Kurds when people like him are under threat from HTS.

He said all he wants is to keep his family safe.

"Over the last eight years, I lost my education and our dreams and everything," he said. "I know we started by asking for freedom, but all we want now is to stay alive."

*His name has been changed for security reasons.