Syrian government forces and allied militiamen are advancing on the largest remaining rebel-held territory in the country's north, forcing thousands of civilians to flee toward the border with Turkey in freezing winter temperatures.
The offensive on Idlib - a large province in northwestern Syria packed with civilians and dominated by al-Qaida-linked militants - was expected after the defeat of the Islamic State group late last year. Last week, Russia's Foreign Minister Sergey Lavrov said the main military operations against IS in Syria have ended and signaled that the focus would shift to al-Qaida-linked militants.
The Idlib offensive carries significant risks.
The province bordering Turkey is home to an estimated two million Syrians, including tens of thousands of people who fled fighting elsewhere. A full-blown government offensive could cause large-scale destruction and massive displacement.
Turkey, a supporter of the rebels, has deployed military observers in the province as part of a de-escalation deal with Iran and Russia, but that has not stopped the fighting on the ground or Russian airstrikes against the insurgents.
It is not clear how far the current offensive aims to reach, and recapturing the entire province is expected to be a long and bloody process. Opposition activists say the main target for now appears to be the sprawling rebel-held air base of Abu Zuhour, on the southeastern edge of the province, and securing the Damascus-Aleppo road that cuts through Idlib province.
Over the past two months, troops backed by Russian airstrikes have captured more than 80 towns and villages in the northern parts of the nearby Hama province and breached Idlib itself for the first time since mid-2015.
The offensive gained more intensity on Christmas Day, when one of President Bashar Assad's most trusted and experienced officers took command of the operation to extend the government's presence toward Idlib and boost security for the road that links the capital, Damascus, with Aleppo, Syria's largest city.
Brig. Gen. Suheil al-Hassan, also known among his troops as "Tiger," has led elite forces to many victories against insurgents since the conflict began nearly seven years ago. He has been credited most recently with the defeat of IS in much of eastern Syria, including the months-long battle for the city of Deir el-Zour.
"Conditions on the ground are wretched for the rebels," said an opposition activist based in northern Syria who asked to be identified by his first name, Hassan, for fear of reprisals by insurgents. He said rebels are stuck in a two-front battle with government forces and remaining pockets of Islamic State militants. He said the Russian airstrikes have exacted a heavy toll.
Another opposition activist based in Hama province, Mohammed al-Ali, said the Russians and the Syrian government are "carpet bombing" villages before pushing into them.
"The Russian airstrikes, weak fortifications and Islamic State attacks in Hama" have all helped government forces, he said by telephone.
Hassan and al-Ali said it is highly unlikely that government forces would march toward the provincial capital, also named Idlib, because it would set up a costly battle with highly experienced and well-armed al-Qaida-linked insurgents. The province is dominated by the Levant Liberation Committee, which claims to have severed ties with al-Qaida but is widely believed to still be affiliated with it.
Al-Hassan's chief mission for now appears to be securing the Damascus-Aleppo road.
In December 2016, Assad's forces captured rebel-held parts of the city of Aleppo, marking the government's biggest victory since the conflict began. The main road to the capital remained perilous, however, with insurgents attacking it from the west and IS from the east. The troops have since driven IS back, but the western side remains exposed.
Four days after al-Hassan took over operational command, troops managed to break through the militants' heavy defenses and capture the town of Abu Dali, a link between Hama, Idlib and Aleppo.
Since then, thousands of people have been fleeing with their belongings amid harsh cold weather toward safer areas further north, including Idlib city and areas near the border with Turkey. Pro-opposition media say that more than 5,000 families have fled the violence over the past two weeks, some renting homes or staying in tents in open fields, others left homeless.
Last week, government forces advanced to within around 12 kilometers (8 miles) of Khan Sheikhoun, where a sarin nerve gas attack killed more than 90 people last year, prompting the U.S. to launch a missile attack on Assad's troops. Experts from the U.N. and other monitoring groups blamed the chemical attack on the government, which denied responsibility.
The Britain-based Syrian Observatory for Human Rights, which monitors the fighting through a network of activists, says that some 43 civilians, 57 militants and 46 pro-government forces have been killed since the offensive led by al-Hassan began on Dec. 25.
"The regime wants to take the eastern part of Idlib province," said the Observatory's chief, Rami Abdurrahman. "Their aim is to remove any threat to the road" between Damascus and Aleppo, he said.
Al-Hassan, a general with the country's powerful Air Force intelligence service, has led elite forces to victory in Aleppo and across much of eastern Syria. Russian President Vladimir Putin praised al-Hassan during a visit to Syria last month, where he met him along with Assad and Russian officers at the Hemeimeem air base.
"Your Russian colleagues told me about your work and that you and your soldiers carry out the missions effectively," Putin told al-Hassan as Assad and Russian officers looked on. "I hope that this cooperation will bring more success in the future."
