Yes. And there has been continual war for 30 000 years over land and expanding one's tribe. The resulting mess is that everybody has a historical claim to everything. Do you like war? Does anybody like war? No. So what's the solution? It's to accept the current arbitrary borders and everybody agree to keep them that way. That was the whole point of the UN, EU and NATO. That was the fundamental underpinning idea of all of them. To stop imperialists trying to expand their borders, no matter what flag or reason.
Stalin just behaved like any minor medieval king. A constant push to expand borders. Lenin was all about uniting the international workers of the world. Stalin had no patience with any of that. He just wanted to be a potentate with as much power as possible. Stalin was the worst thing that could have happened to the USSR.
OK; so if you think that keeping the current borders is the best option, then why are you advocating an invasion?
You seem to want to keep, not the current borders, but the borders as they were a few years ago.
How did you decide on a date at which to fix these borders? How can you expect any agreement on a given choice of date, when a different choice would be hugely advantageous to so many interested parties?
It's a nice idea; but how can it be made to work?
If you pick a date in the past, people will demand a date that's further in the past, then others will demand a date that's further still, and you will never get agreement.
If you pick a date in the future, to allow time to get everything set up, then everyone will immediately go on an orgy of land-grabs, in the hope of having the biggest share when the music stops.
If you pick today, right now, this minute, then how do you even know where the borders of areas currently in dispute are? And how do you get the news out to everyone? If it takes a week for the news to reach a disputed territory, the guys who hold it a week from now are not going to be happy to hand it back to the guys they just spent a week being shot at by to get it.
Perhaps you could hold a lottery and draw a (recent) historical date from a hat; but I can't see many governments agreeing to a deal where they don't know if they might lose some territory that they consider particularly valuable or important.