Battle for Aleppo: A turning point in Syria's civil war? (part 1)

It's shaping up as a turning point in Syria's civil war. After years on the back foot, the Syrian army advances on what was once the country's largest city, Aleppo. The Assad regime is backed by Russian air strikes, Lebanese Hezbollah forces and Iranian fighters on the ground. That's triggered a fresh exodus towards the now closed Turkish border. Are the latest advances jockeying for position ahead of new negotiations on Thursday, or are talks just a smokescreen for Damascus and its allies?