The fragile cease-fire in Idlib —- in place since early March when a Turkish-Russian deal ended a violent escalation — seems to be teetering on the brink of collapse amid growing signs that the Syrian regime is gearing up for a fresh thrust to capture the rebel stronghold.

The truce has largely held despite sporadic violations, but appears doomed mainly because southern Idlib remains far from being stabilized. In their meeting in Moscow on March 5, the presidents of Turkey and Russia agreed to establish a security corridor 6 kilometers (nearly 4 miles) deep on either side of the M4 highway to reopen the key road to traffic. Turkish and Russian forces have conducted more than 25 joint patrols along the route since then, but failed to fully take it under control. The road has yet to reopen to transport and trade. The failure of the plan owes to radical elements who skillfully disguise themselves among the region’s people and enjoy the support of some locals. 

Under its deal with Moscow, Ankara promised to moderate the armed rebels in Idlib and purge the region from the radical ones. But despite Ankara’s efforts and the joint patrols, the radicals remain in the region. 

For almost a month, the forces of Syrian President Bashar al-Assad have been increasing their military buildup to Idlib from the southeast and Deir ez-Zor. Many see this as the omen of a forthcoming onslaught to purge radical factions from the Ghab Plain and Zawiyah Mountain, which dominate southern Idlib, and establish a firm grip over the cleared area.