They wouldn’t have had to had they not become allies with Hitler in 1939. All because Stalin wanted his revenge on Poland.
That’s probably somewhat true. But it’s also somewhat disingenuous. The fact is, Poland had only existed for 20 years. The Russians got back what had been under the czar for 200 years. But I think the bigger goal for the Russians at that time was to try to delay a war with Germany that the USSR was ill prepared for after Stalin‘s purges. It’s probably a big stretch to say World War II would’ve never happened.
Germany was on the march and the war was coming either way.