Russian troops fighting alongside Assad, maybe. But against ISIS? Where’s the evidence for that? There are a whole bunch of rebel groups and ISIS’ power base is well away from where the Assad regime is - more likely they’re fighting other groups.
Based on Israeli news source. http://www.ynetnews.com/articles/0,7340,L-4696268,00.html Russia has begun its military intervention in Syria, deploying an aerial contingent to a permanent Syrian base, in order to launch attacks against ISIS and Islamist rebels; US stays silent.