According to some sources, Russia may actually be assisting ISIS to a certain extant. (http://www.Theguardian.Com/world/2015/oct/10/russian-airstrikes-help-isis-gain-ground-in-aleppo)
As you can see ISIS is actually gaining ground in many areas as the Russians batter their opposition. The Russian airstrikes are mostly attacking bases belonging to those opposing the Assad Regime leading to more ISIS victories.
It is becoming more and more apparent that the US engagement in this strife has been primarily motivated by anti Russia concerns as personified by the Assad Regime in Syria. ISIS has been the rhetorical 'sound bite' to deflect public attention away from this covert strategic objective. Correct me if I need correction on this point. ISIS is not 'top of the list' and hence the 'feigned urgency ' and political posturing that we have been fed for years now in Iraq.
Here are some facts
Moscow's alliance with Damascus dates back to 1955, when the Soviet Union struck its first deal to provide arms to Syria, and since then it has been Syria's main military suppliers, to the tune of hundreds of millions of dollars over the decades. Moscow helped rebuild Syria's military after its disastrous wars with Israel in 1967 and 1973. Syria is home to Russia's only naval facility in the Mediterranean, a base at Tartous. Since the Syrian civil war erupted in 2011, Russia has been a chief backer of Assad, fending off U.N. resolutions against him and stepping up arms deliveries to his military.