All I know on this subject is what public school taught me, which I have to throw into doubt to be epistemologically rigorous. Good question. I should like to find that answer.
Discussion
It's my understanding that the Nazi defense at the Nuremberg Trials was that they did kill those Jews, just that Jews were technically not people. Sounds like Holocaust to me. But I'll refer to the documents on that sometime soon to see for myself. It seems to me like it was a bit of a coverup for Soviet wrongdoing and a bit of actually happened. The Soviets have been relentlessly favored/ignored by media.