Will Syria's war be won or lost in Aleppo?

Syrian rebels fight for their survival as government forces move in on the city, backed by Russian air strikes.




It is the clearest example yet of the impact Russian bombing is having in Syria.

Hezbollah and other fighters loyal to President Bashar al-Assad, backed by Russian air power, are advancing on Syria's largest city Aleppo.

The fall of Aleppo could be a significant setback for rebel forces. They have managed to hold on to much of the city since 2012, but could now find themselves completely surrounded.

The rebels say that without outside help, Aleppo will fall. Saudi Arabia, Bahrain and the UAE say they may send ground troops. But it is unclear when or how that would work.