Eh, it was more complicated than that. Basically a gradual build up from 1918 advancement of Polish forces from west and Soviet from east into the territories abandoned by German armies, then "border incidents" then regular army clashes, and eventually a full blown offensive by Poland and counteroffensive by Soviets.
I guess you can interpret it as Poland invading soviet russia (no soviet union yet btw, and Poland was supporting one of the 3 Ukrainian states that existed at the time).
But yeah Poland wasn't innocent anyway. For example it did the Putin's Crimean trick on Lithuania back in interwar. That was much more clear-cut.
> In any case, Eastern Europe is deeply plagued and poisoned by all of this past violence. No one is able to have a mea culpa moment, no one is able to admit their own guys were bloody murders often killing thousands of people like cattle. No one can admit their ancestors crap.
That's just false.
https://en.wikipedia.org/wiki/Giedroyc_Doctrine
Poland did mea culpa after WW2. The whole thing is based on recognizing that Poland has been imperialist and did bad things and that it's in the end bad for Poland to continue trying to control these territories because it pushes us into conflict against Russia without the support of the other countries.
On the other hand admiting guilt and renouncing imperialism makes us clearly the lesser evil for the countries in between and gives us buffer zone in case Russia turns evil again (which we predicted, and which did happened).
It was the basis for Polish eastern foreign policy for last 37 years and still is (it's another question for how long it stays that way if far-right wins the next elections tho).
I highly recommend anybody interested in Eastern Europe after WW2 to read Giedroyc and Mieroszewski. They were visionaires. They predicted back in 1950s that USSR will fall and that the independent nationstates that will appear will have 2 choices - go back to chaotic ethnic wars or drop the territorial and historical disputes. And they developed the doctrine in 70s and slowly persuaded opposition in communist Poland so when Poland regained independence in 1989 - almost all the elites bought into it. It was a big bet and it worked very well for Poland.
Sadly nowadays half of Polish political scene starts to move away from that, but that's another subject. Mostly just unchecked far-right propaganda.