[sobieski]

Actually, it was started in 1939 when Polish priests, intelligentsia and professoriate were arrested and put into the newly created Auschwitz.

[buck jarret]

By “in earnest”, I meant extermination of Jews by the thousands.

[SJackson]

Actually, it was started in 1939 when Polish priests, intelligentsia and professoriate were arrested and put into the newly created Auschwitz.

I would have suggested 1933, with the newly created Dachau, which housed German political "dissidents", soon followed by the Nuremberg laws.