Back in February the ceasefire in Syria provided an opportunity for the Nusra Front to push from its stronghold in Idlib Province into the neighboring Aleppo Province. Half a year later, that influx has left Nusra with substantial territory, including being the leader of a force of rebels that controls half of the city of Aleppo itself.
The Syrian military has struggled to cope with this for some time, but a few weeks ago appeared to have the situation well in hand, surrounding the Nusra districts and cutting off their supplies. Over the weekend, their fortunes shifted, and Nusra took an artillery academy, reopening their districts and threatening the half of the city under government control. This is dramatically complicating Syria’s strategy in Aleppo.
With many hundreds of Nusra reinforcements arriving from Idlib, the momentum is now in their favor, and while Syria is scrambling reinforcements of their own, they can no longer just siege the rebels and wait them out, as they’d been inclined to do in previous situations, waiting for a good opportunity to move in.
At the same time, Aleppo has seen large civilian casualties inflicted by both sides, and an escalation of the protracted battle would be a recipe for even worse casualties, and growing international disquiet. That’s unlikely to suit either Syria’s government, or their allies in Russia, and will likely prevent them from trying to go in, guns blazing, in a major attempt to expel Nusra and its allies in short order.