Russia's only base in the Medeterian is in the Syrian port city of Tartus and Russia also buys oil and sells weapons to Syria and they don't want to lose Assad unless they can be sure they will have the same cosy relationship with his successor. As long as there is no foreign intervention then provided Russia keeps providing him we weapons then Assad still has a chance at survival. Its only of it comes to a military showdown with the west that Assad is sure to going to have a chance at survival if he can start taking back the territory he lost. The smart thing for him to do would be to provoke Hezbollah into picking a fight with Israel get the Syrian people focussing their anger on Israel giving Assad to plan his next move. Old tried and tested trick I am just surprised he hasn't tried it yet Russia is playing a dangerous game though in giving to much support to Assad because when he falls whoever replaces him might see Russia as an enemy for supporting Assad and kick them out of Tartus.