“Tried to get Poland too but lost that fight.”
I’m much more a fan of Poland than the Soviet Union, but more than a few Poles have told me that Poland was trying to get Belarus/Ukraine instead. I don’t know the truth, but the allies who went to war in 1939 to support the Poland created by Versailles didn’t see fit to join them in their “defense” against the Soviet Union in 1920 (and neither did the US).
I guess I'm not sure why you put the word defense in quotation marks. There was a war in 1920 between the Poles and Soviets and it reached the gates of Warsaw. It was quite real.
That is what started the fight but, even after the Poles had retreated from Belorus/Ukraine, the Soviets tried for Warsaw. And got beat bad enough to seak terms...