I think the depth of systemic cruelty and viciousness was reached well before the 1940s. However colonialism and its precursors the Crusades, the Reconquistá and the Counter-Reformation have been sanitised to the point that the 20th century can be called the century of myopic mass murder. Europeans jealous of the slaughter they visited on other continents nostalgically soaked their own continent with millions of litres of blood starting in 1914. Fully exhausted the "discovered" development aid and handed the cross and flame to the crusaders of North America in whose train they followed/ follow to this day.
Mit freundlichen Grüßen/ Cordialement/ Cordiali saluti/ Yours sincerely/
Dr. Patrick Wilkinson
Cognitive Consulting and Language Logistics