I agree with most of what Norman and Francesco say. But I think Putin’s moves in Syria were driven by the failure of the New Axis of Evil to cope with the serious threat of the defeat of Assad. Iran hasn’t been able to dominate the battlefield, to put it mildly (significant # of Iranian/Hezbollahi commanders killed of late, along with cannon fodder in the raniks), and the Russians are trying to salvage the situation. Why? Because if Assad were defeated, Russia would be threatened with a) loss of bases in Syria, b) severe threat to Iran (where do you put Hezbollah and Quds in your own region, and the restive Iranian people might see the hated regime humiliated by Sunni terrorists).
So you’ve got Iranian ground forces supported by Russian bombers and some special forces. What’s next? Bombs in Moscow and Tehran? What if the Axis loses, in other words? AQ and ISIS fight well and are smart…don’t assume Putin has a free hand just because America is absent. Islamists beat the USSR after all, and the foreign assistance they are getting nowadays may be on a par with what they got back then.
Life is full of surprises.