This question came to my mind while reading a recent post in a thread about the WWII IMT that mentions the Soviet liquidation of Polish POWs with the intent of killing off potential political enemies. Have such brutalities been "good policy" from a perspective of politics, power, cultural identity, etc? Obviously not morally good, but successful in a realpolitik sense.

As this subreddit frowns on "throughout history" and "throughout the world" questions, I'll tentatively ask about 20th century eastern and central Europe, but if any of you historians can speak to other times/places I'd love to read your answers too (e.g. Assyrian resettlement, Sparta's helots, ethnic strife over territory in Japan, etc).

And just to at least try to head off inappropriate posting, please remember THE RULES, especially "We will not tolerate racism, sexism, or any other forms of bigotry," the violation of which is a FIRST-OFFENSE BAN in this subreddit, and the "no soapboxing" rule. Do not post unless you are a qualified historian!