I've been seeing articles like this one today:
ISIS left so weakened by airstrikes and desertion it could be wiped out in just HOURS
Maybe that's a bit overly-sensational. But it appears as if the Russian military means business.
The response from the west (the US included) has been more along the lines that "Assad is worse than ISIS":
It seems as if the west is trying to "thread the needle" -- that is, degrade ISIS while not giving Assad any advantages. Russia doesn't feel the west's sense of propriety.