Eastern Aleppo, the rebel-held half of what was once Syria's biggest city, is falling. Once the resistance there collapses, things may move very fast in Syria, and the biggest question will be do the outside powers that have intervened in the war accept Bashar Assad's victory, or do they keep the war going?
Even one year ago, it seemed completely unrealistic to talk about an Assad victory. The Syrian government's army was decimated, demoralized and on the verge of collapse: Every time the rebels attacked, it retreated.
There was even a serious possibility that Islamic State and the Nusra Front, the extreme Islamist groups that dominated the rebel forces, would sweep to victory in all of Syria. But then, just 14 months ago, the Russian air force was sent in to save Assad's army from defeat.