A three-month aerial bombardment campaign by Syrian regime forces and Russia, combined with a ground assault on the last jihadi stronghold, is largely deadlocked, leaving thousands of people dead and displacing hundreds of thousands more, with no clear end in sight.
The fierce fighting threatens to unravel a fragile truce deal struck in September by Russia and Turkey as the Syrian regime vows to retake all territory outside of its control and Ankara doubles down to protect its influence in the northwest of the country.
On April 30, Syrian government forces backed by allied militia and Russian air power launched an offensive against rebel and jihadi factions led by Hayat Tahrir al-Sham, al-Qaida's former Syria affiliate, in northwestern Idlib province, as well as parts of the neighboring provinces of Aleppo, Hama and Latakia.
Read more: Buffer zone in Idlib
Moscow and Damascus ostensibly launched the offensive in response to what officials said were jihadi forces carrying out multiple assaults — including a dozen attempts to attack Russia's Hmeimim air base using drones and missiles.
According to the UK-based Syrian Observatory for Human Rights, at least 2,747 people have been killed in the fighting since late April, including 824 civilians, 997 rebel and jihadi fighters, and 926 members of regime forces. The regime's losses have put strain on a hollowed-out force weakened by years of casualties and defections.
"The Syrian government aims to retake the entirety of territorial Syria, a goal that is difficult, but — over Damascus's unlimited time frame — not impossible," said Sam Heller, a Syria analyst at the International Crisis Group (ICG).
One strategic goal of Syrian President Bashar Assad's is to secure the M4 and M5 highways running through Idlib, vital arteries that connect the government-controlled cities of Aleppo and Hama and the regime's Alawite heartland in Latakia on the Mediterranean coast.
The stalled campaign, however, has revealed the limits of the Syrian and Russian air power as they resort to a strategy of bombing scores of schools, hospitals, markets and bakeries in an effort to sap local support for the opposition. It is a strategy that has been hardened on the gruesome battlefields of Syria's eight-year civil war.
With the military support of Russia and Iran, the Syrian regime has retaken most opposition-controlled areas over the past three years using a strategy of long-run sieges and assaults. Many opposition fighters, their families and civilians were transferred to jihadi-controlled Idlib under so-called reconciliation deals between the government and rebels.
Now, with rebels of various stripes confined to Idlib, "the Russian and Syrian goal is to destroy Idlib province, dividing rebels and civilians before a ground offensive after a few months of shelling and bombing," said Fabrice Balanche, a professor at the University of Lyon who has written extensively on Syria.
Idlib is home to about 3 million people — half of whom have been displaced from other parts of Syria. On Friday, the UN reported that 400,000 people have been displaced in the region in the past three months. Many have flee to crowded camps on the Turkish border or sleep out in the open.
Politically, the situation in Idlib is riven by the interests of competing and cooperating foreign powers on the ground — namely Turkey, Russia and Iran — all of which have leverage to put the brakes on the Assad regime's goal of recapturing lost territory at any cost.
"The main obstacle Damascus now faces is the complicating role of foreign forces in the areas still outside its control," the ICG's Heller said. "In Idlib in particular, Russia has to balance its support for its Syrian ally against its agreement with Turkey on Idlib and Turkish-Russian ties more generally."
"There seem to be limits to how far Russia can militarily escalate in Idlib without prejudicing its relationship with Turkey," he added.
A September truce deal between Russia and Turkey envisioned the creation of a demilitarized buffer zone between regime and rebel-controlled areas and an as-yet-unfulfilled commitment by Turkey to isolate and combat jihadi groups.
The agreement was reached amid international concern that an offensive by the Syrian regime would send a flood of refugees and hardened extremist fighters to Turkey, which already hosts more than 3.5 million refugees, and potentially onward into Europe.
"Turkey is loath to take al-Qaida and its fellow travelers head-on because that would mean devoting Turkish military resources to Idlib and possibly creating hundreds of thousands of displaced people who would immediately head toward Turkey," said Nicholas Heras, a Middle East security fellow at the Center for a New American Security, a think tank in Washington, DC.
"The Turks oscillate between wanting Idlib to be its own rebel-ruled zone that makes peace with Damascus to building the foundations for an enduring Turkish presence in Idlib," he said.
The Syrian regime assault has been hampered by Turkey, which has reinforced its dozen military observation posts along the perimeter of Idlib and increased shipments of weaponry — including anti-tank TOW missiles — to rebel factions it supports. The Turkish military has also fired artillery on Syrian regime positions on several occasions when its observation posts came under attack, signaling a readiness by the NATO member to maintain its influence in the northeast.
"To preserve Idlib, Turkey has wagered on its bilateral relationship with Russia, but also on a rebel force inside Idlib that is strong enough to make any attempt to overrun Idlib and trample Turkish interests unacceptably costly for Damascus," Heller said.
The escalating fighting in Idlib has given renewed impetus to reviving the ceasefire under the so-called Astana process when the guarantor powers Turkey, Iran and Russia meet in Kazakhstan on August 1-2.
"The hope is that Turkey and Russia are able to arrive at an understanding that de-escalates the area's violence," Heller said. "But, even then, they'll have to bring their respective Syrian partners on board with a restored ceasefire, and there are Syrians on both sides who are not obviously controllable."