Stoping Isis does seem to be fairly simple and progress can be made as seen with the Russian example. The only reason Isis did well is because certain nations were funding them and allowing them to trade the oil while simultaneously being obsessed with toppling Assad. Another example, the French are back in Syria, but for some reason only seem to be able to hit civilian structures not being able to see the oil truck convoys or anything truly suspicious. You beat Isis by getting real and giving Assad control over his country again. It really is that simple. Oh, and by closing the borders and sending people back home to Syria after compensating Assad for all the mayhem.