Pure anecdote and likely shaded by the Cold War, but I remember my WWII veteran grandfather (European theater) telling me how after the war he had talked to fellow US and British officers responsible for turning POWs over to the Soviets. (I don't recall if he said whether they were the soliders of Axis powers being turned over to the Russians under some agreement, or soldiers from Russia or from Soviet occupied countries.) He recounted how the Soviets made no secret of the fact that the POWs were executed en masse, and the Allied officers responded by helping their own prisoners escape rather than hand them over to certain death.
If you were a German with an armpit tattoo [i] and were taken by the Russians death was certain. The allies would routinely hand over these men to the Russians to avoid an entire war crime trial.
