US pullout: what impact for Syria's main players?

US President Donald Trump's decision last week to pull troops out of Syria could have far-reaching repercussions for the multitude of parties involved in the conflict.After a call with his Turkish counterpart Recep Tayyip Erdogan, Trump appeared to be passing on responsibility for the fight against the Islamic State group (IS) to Turkey.If it fills all of the security vacuum left by the US and its current Kurdish allies, Turkey, which already has sway over northern regions, will extend its influ