if you look at a map, russia looks big and scary. but, the truth is that it's mostly trees. the core of russia is really not that much bigger than turkey. but, keeping with this logic, you have to realize that the eastern half of turkey has little allegiance to the western half. this, however, does not balance out. russia's much larger size is not a serious advantage.
a serious conflict is not going to come down to brute strength, but to technology and tactics. the russians are always two steps behind the americans, but they're several steps ahead of the turks.
the way this would work is that the russians would dismantle their military from a distance, using a variety of missile-based tactics. if you've seen them hitting targets in syria from ships in the caspian, that's the kind of thing i'm talking about. they'd probably rely mostly on kurdish foot soldiers. and, if they're lucky, greek foot soldiers. with the proper air and naval support, they could likely collapse the state without setting foot on the ground. they'd then parachute in, afterwards.
but, to do this effectively, it has to be done quickly in order to overwhelm them before they can bring in more advanced defense systems from the americans. further, it should not be forgotten that the united states keeps nuclear warheads on turkish soil and that this could be a strong enough deterrent to prevent what i just said from actually happening.
so, what we have here is kind of the wrong comparison. if it comes down to this, the russians are going to use their technological superiority, rather than rely on overpowering them through ground combat. but, it's very hard to see how the americans let that happen. and, they don't have to do a lot to stop it from happening, either - they just have to remind putin where those warheads are pointing.
.....and that is, after all, why turkey joined nato, and why nato put those warheads where they are.
it's exceedingly unlikely. granted.
but, i have to say that it would be interesting to wake up one day and look at a map and see the name constantinople on it, at the center of a neo-byzantine state.
if you have a soft spot for narratives about historical purposes, however unscientific it may be, russia could then cease to exist. it will have accomplished it's purpose.