But I think the same pattern is found everywhere. Most cultures were much more violent in the past. I think Pinker wrote a book about the phenomenon, he is good (I haven't read that but others).

(Let me note that reading about the Polish deluge was one of the shocks of my life, the Swedish school system really didn't mention much about the Polish side of it. I guess the Germans are the only ones that ever took any form of responsibility for historical atrocities.)