It was unsustinable even before war with rising death, emmigration. All eastern Europe suffers from that, and what Cosovo conflict caused to ex-Chechoslovakia (did you ever wonder why so many pornstars came from here?), would happen to Ukraine, Russia and Belarus. And it would be particularly damaging to Russia, a country that spans across 8 timezones yet having half the people US have. There’s many ghost cities already, and I can imagine a lot more would die off, and with them the last industry this country inherited from USSR would die too. It’s a national sepuku. In ten years this place would resemble New Vegas, with everything concentrated in the capital and nothing everywhere else.