Dubai: Having recaptured most of Syria, Bashar Al Assad is in a buoyant mood. His oft-threatened assault on Idlib, the most prominent province that is almost totally out of regime control, materialised on Thursday, with regime forces shelling the province, in addition to rebel areas in Hama and Aleppo provinces as reinforcements arrived. At least 30 people were killed in the three provinces.

In Idlib, the artillery and rocket fire slammed into areas near Jisr Al Shughour, a key town in the southwestern part of the province, according to the Syrian Observatory for Human Rights. “The shelling is in preparation for an assault but there has been no ground advance yet,” said Observatory head Rami Abdul Rahman.

“Regime reinforcements including equipment, soldiers, vehicles and ammunition have been arriving since Tuesday,” he told AFP.

They were being distributed along three regime-held fronts, including in neighbouring Latakia province just west of Jisr Al Shughour, in the Sahl Al Ghab plain that lies south of Idlib, and in a sliver of the province’s southeast that is already in regime hands.

Idlib is densely populated, thanks to innumerable ‘transfers’ of rebel fighters from other Syrian provinces under deals with the regime and its Russian and Iranian allies. It also hosts the largest concentration of armed men bitterly opposed to the regime in Damascus — the kind of people who are likely to fight to the death. Above all, Idlib borders Turkey, and Ankara has a military presence in the province in the form of 12 observation posts. The province forms a “de-escalation zone” agreed in 2017 by Turkey, Russia, and fellow regime ally Iran, meant to prevent hostilities there.

All this indicates that the military assault on Idlib, which has apparently started, could be more devastating than any of the previous battles. As Syrian regime forces recaptured other pockets of territory, the battles were settled by evacuating rebels to Idlib, which now contains as many as 70,000 fighters. That is the biggest concentration of opposition fighters yet assembled. Idlib shares a 100km border with Turkey and fell to extremists and rebels in 2015. Now, around 60 per cent is held by Hayat Tahrir Al Sham (HTS), led by militants from Al Qaida’s former Syria affiliate. The rest is controlled by rival rebels, while regime forces hold a southeastern sliver.

There are also an estimated three million civilians in Idlib, many of whom took refuge there after fleeing fighting elsewhere in the country. An assault on Idlib could trigger Syria’s largest humanitarian crisis yet and a prompt a new exodus of refugees to Turkey and perhaps to Europe, analysts say.

Given the uniqueness of the situation in Idlib, Russia’s own Syria envoy Alexander Lavrentiev said recently there was “no question of an operation” on Idlib. But the fact that Al Assad has fired the first salvo indicates he has at least some form of approval from Russia. On Thursday, the regime dropped leaflets over Idlib, urging people to agree to a return of state rule and telling them the seven-year war was nearing its end.

Idlib’s strategic importance for the regime lies at least in part in the M5 highway, which links second city Aleppo in the north to Damascus, and then south to the recently recaptured Nassib border crossing with Jordan.

Nicholas Heras, an analyst at the Centre for a New American Security, told AFP about the regime’s main obstacle in Ankara.

“The greatest impediment to Al Assad in Idlib is Turkey and the Turkish government’s policy towards northwest Syria,” he noted.

Throughout Syria’s seven-year war, Al Assad has pledged to recapture every inch of the country. After Turkish troops intervened in 2016, Damascus regularly lambasted them as “occupiers”.

Turkish President Recep Tayyip Erdogan is wary an assault could push thousands of people to the frontier, much like what happened along the Jordanian border in June when troops began attacking southern Syria.

Nagar Oliver of the Turkey-based Omran Centre said he expected Russia, Turkey, and Iran “will not allow any kind of large-scale war in the north, because that will affect everyone there”.

“War cannot be allowed to go to Idlib,” said Jan Egeland, a top UN humanitarian adviser on Syria.

The UN has appealed on Turkey to open its border to refugees, Egeland said.

Even as the war enters its final stages, the risk that it could ignite a wider conflict has not passed, analysts say.

It will fall to Russia to steer Syria through the pitfalls ahead, as the only outside power to enjoy good relations with all the countries that have a stake in the Syrian war, including Israel and Iran. After intervening in the conflict in 2015 to save Al Assad regime, Moscow has largely succeeded in balancing the competing interests of the various players, tamping down fears that the conflict could ignite a regional conflagration.

But Russia’s capacity to manage these competing concerns is limited and will be tested by the coming battles, said Riad Khawija, who heads the Dubai-based Inegma defence consultancy.

“Russia is not as much in control as it likes to appear,” he said, citing the apparent failure of recent Russian diplomacy aimed at addressing Israel’s concerns about Iran’s presence in Syria.

“Iran has invested so much in Syria, it’s not going to leave now, if ever,” he said. “So with Iran refusing to get its forces out of Syria and the Israel insistence that it leave, eventually there is going to be a clash.”

Damascus and Moscow justify bombing Idlib by pointing to the presence of the extremists from Hayat Tahrir Al Sham, designated as “terrorists”.

Ankara wants to prevent the two countries from using the same excuse for a ground assault, says Heras.

“The Turks are holding the line that Hayat Tahrir Al Sham is Turkey’s matter, and not an issue that Al Assad can use to launch a war on Idlib. But there is a time clock that is running now,” says Heras.

Recently, Islamist heavyweights Ahrar Al Sham and Nur Al Deen Al Zinki merged with four other rebel factions opposed to Hayat Tahrir Al Sham to form the National Liberation Front.

“Sooner or later, if the Turks want to stay in Europe and America’s good graces, Erdogan is going to have to act more decisively against the terrorist organisations in Idlib,” Heras said.

Ultimately, to avoid a full blown regime assault, Oliver said, Turkey may wage “a military operation inside Idlib to eliminate the hardliners among Hayat Tahrir Al Sham and other extremist groups”.