There is no downside for Russia in destroying ISIS. None.
Iran likes them more. The troops get a warm-up game for Ukraine and the Baltics. And a lot of terrorists who might want to do another Beslan get dead.
It all makes perfect sense.
Ah, the two front war. If we had a US President with brains, and who actually acted in the national interest, we could spend Russians into submission and get a lot of their troops killed inside of a calendar quarter.
Oh, and Angela - lots of room for Syrian refugees in the Saudi Kingdom. Maybe you forget how the Berlin Airlift worked. Do the same again, only this time in reverse.
Syria becomes a part of an expanding new USSR, which already took over part of Ukraine and Crimea.