When are you referring to? Because it was a German/USSR alliance which started the war by invading Poland .. and then switched sides to Allied aid to USSR to fight Germany .. and then back again immediately once Germany was defeated. All very realpolitik. USSR had no interest in a free Eastern Europe either.

The "rewriting" is literally what happened.

https://en.wikipedia.org/wiki/Molotov%E2%80%93Ribbentrop_Pac...

https://en.wikipedia.org/wiki/German%E2%80%93Soviet_military...

And it started in 20s already: https://en.wikipedia.org/wiki/Treaty_of_Rapallo_(1922)

Soviet russia helped Germany work around the military restrictions that were placed on them after WW1.