^It worked really well for the Russians... Thanks to that, at the end of the day, the Russians could beat Hitler and rescue the Europe from him.
It was not so easy to manage after the "Munich Betrayal" the year before Munich Agreement - Wikipedia
and the German–Polish Non-Aggression Pact German–Polish Non-Aggression Pact - Wikipedia
Both of the "clever" treaties had opened the way for Hitler to the East, giving him green light, not that anybody in Europe was much concerned of...