I don't disagree - but I think you (and maybe the Russians themselves) are missing the Holy Roman Empire (what eventually became the Austro-Hungarian Empire) and so are fourth. I haven't really dug into that Empire (other than an interest in how the Hapsburgs married themselves into power), but my take is that the Germanic tribes that conquered Western Rome carried (or at least thought they were carrying) the mantle of Empire moving forward.

That aside, I expect that Ukraine is going to be a difficult place for Russians for the next couple of decades - and that they are going to have difficulty getting grain grown and sent to the Russian Federation. NATO nations can't step in, but they can do what the US did in the 70s in Afghanistan, only now portable weapons are a lot more capable (e.g. Javelin, Stinger, etc.)

Also, given the terror campaign the Russians are now conducting - and the RF passports they were handing out at one point so has to have 'ethnic Russians' in need of rescuing, it's just a matter of time before someone who has nothing left to lose - and holds one of those RF passports makes their way to the RF and terror makes its way to the RF homeland. I hope that doesn't happen as it represents the death of more innocents - and will make eventual separation more difficult for Ukraine,