It took years for Bashar al-Assad’s forces to take back Syria’s second city. But it took only days for Islamist rebels to overrun Aleppo. Why has a conflict that has been effectively frozen for four years suddenly sprung back to life? What to make of Hezbollah, which says it won’t be sending help for now as it’s pinned down at home by a precarious truce with Israel?

What role for Assad-backers Russia and Iran? And what role for Turkey, which backs some of the rebel groups with an eye to pushing Syrian Kurdish forces away from its border? Recep Tayyip Erdogan last summer offered a deal with Damascus, which Assad turned down on the grounds that it would mean ceding the nominal sovereignty he has over a territory never really recaptured in eleven years.

Back then, it was the Arab Spring and the leader of a hereditary dynasty who looked ready to fall, but Assad proved predictions wrong. Could this time be different? If so, how?

Produced by Alessandro Xenos, Rebecca Gnignati and Ilayda Habip.