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After seven brutal years of war, all signs are pointing to a final showdown in Syria. The regime of President Bashar al-Assad, buoyed by support from Russia and Iran, has systematically reclaimed territories once in the hands of insurgents. Now it is preparing an offensive against the last rebel enclave: Idlib, a largely rural province that abuts the country’s northwestern border with Turkey.

International observers are warning of a potential humanitarian catastrophe. “There is a perfect storm coming up in front of our eyes,” said Staffan de Mistura, the United Nations' envoy to Syria.

Roughly 3 million people live in Idlib, more than half of whom are Syrians displaced from other parts of the country. As rebel bastions fell to Assad's forces in other parts of the country, tens of thousands of civilians trapped in those areas agreed to be evacuated to Idlib as part of cease-fire deals brokered with the regime.

The province became a hotbed of the Syrian opposition, including a number of Islamist militant factions that dominate the enclave. The most powerful is Hayat Tahrir al-Sham (HTS), an Islamist militant group formerly affiliated with al-Qaeda that has participated in terrorist attacks and the killing of civilians. Idlib is also home to vast camps of displaced people and endemic poverty — as many 1.6 million people in the province rely on food assistance, according to the World Health Organization.

With Turkey leery of welcoming a new wave of refugees — the country already hosts more than 3 million Syrians — there are growing fears that civilians in Idlib may be cornered. Over the years, hundreds of civilians have been killed there in airstrikes by regime and Russian warplanes.

On Thursday, de Mistura urged the creation of a humanitarian corridor and suggested that civilians consider fleeing back to regime-controlled territory, a proposal representatives of the opposition said was “regrettable.” But such pleas echo the desperate appeals made by the United Nations in the past, entreaties that went largely unheeded as the Syrian regime quashed resistance in Homs, Aleppo, Damascus and elsewhere.

Assad and his allies seem in no mood for compromise this time, either. The regime is talking up the “liberation” of Idlib from thousands of “terrorists,” and my colleague Louisa Loveluck reported Thursday that the Syrian army has been dropping leaflets urging rebels and their supporters to surrender. “Until when will you and your families live in fear and anxiety?” read one. “How long will your children remain without hope or future?”

Russia is equally unyielding. On Wednesday, Russian Foreign Minister Sergei Lavrov described the province's militants as “festering abscesses” that should be “liquidated.” The Russian navy will begin a major exercise in the Mediterranean on Saturday, probably in preparation for an offensive by Syrian government forces. According to Reuters, the drills appear “aimed at deterring the West from carrying out strikes on Syrian government forces."

Washington is struggling to influence events on the ground. The Trump administration seems more immediately preoccupied with the prospect of Islamist fighters scattering farther afield, and it has urged Turkey “to fortify its small presence of outposts [in Idlib] … to help defeat Islamist militant groups,” Al-Monitor reported.

On Thursday, Turkish President Recep Tayyip Erdogan said he was in talks with Russian and Iranian counterparts in a bid to head off the crisis and maintain a cease-fire. Erdogan's position has shifted markedly since earlier stages of the war, when Ankara loudly clamored for Assad's ouster and supported a number of rebel factions. Analysts say he made a losing bet in backing Assad’s downfall and now is coming around to the scenario that he sought to prevent. Though Turkey retains influence over the rebels in Idlib, it has increasingly found common cause with Assad's patrons.

“Moscow wants Ankara to reconcile with the Assad regime,” wrote Joost Hiltermann of the International Crisis Group. “Turkey’s reliance on Russia to protect itself from the [Kurdish separatists] and prevent a new surge of refugees, this time from Idlib, may therefore force it into an accommodation with Damascus that it has successfully resisted until now.”

As my colleague reported, Ankara could isolate Idlib's hard-line factions, such as HTS, by persuading other rebel groups there to accept a negotiated settlement with the Assad government.

“Idlib’s fate now rests with Turkey and Russia,” Loveluck wrote. “Although on opposite sides of the conflict — Ankara supports the rebels and Moscow is one of Assad’s major allies — the two powers share an interest in averting a humanitarian catastrophe. Their diplomacy on the matter is likely to culminate Sept. 7 when they meet in the Kazakh capital, Astana, along with Iran.”

Whatever this diplomatic process yields, the picture for Syrians remains bleak. Outside Idlib, with the war largely won, the Assad government is calling for the millions of refugees living in limbo abroad to come home. But foreign governments and international rights groups warn that conditions are hardly right for return. Many refugees fear reprisal attacks from government loyalists.

"We can’t go back because of [the risk of] neighbors’ petty revenge,” a Syrian refugee in Lebanon told the Guardian. “They snitch on you and call you a traitor and the next thing you know you’re languishing in prison, for nothing. My town is filled with regime forces and thugs. How do they expect me to return?"

He may have had in mind the chilling remarks made by Maj. Gen. Jamal al-Hassan, a senior Syrian military official who is reported to have said last month that “a Syria with 10 million trustworthy people obedient to the leadership is better than a Syria with 30 million vandals” and vowed that the country's “cancerous cells” of resistance will be “removed completely."

Millions in Idlib now are bracing for this final push.

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