Syria: who wants what from the conflict?

As Turkey launches a new offensive over the border into north-east Syria, David Aaronovitch and guests examine what Turkey, Russia, Iran and the US want from the war in Syria. Which country stands to gain the most? And what is President Bashar al-Assad's calculation? Guests include: Suat Kiniklioglu from the Institute for Security and Development Policy in Stockholm. Anna Borschchevskaya from the Washington Institute Seyed Ali Alavi from the London School of Oriental and African Studies Steven Heydemann from Smith College in Massachussetts Lina Khatib from Chatham House.