In 1989, the British historian Richard J. Evans wrote that right from the beginning of the war against the Soviet Union, the Wehrmacht fought a genocidal war of "extreme brutality and barbarism". Evans noted that the Wehrmacht officers regarded the Russians as "sub-human", were from the time of the invasion of Poland in 1939 telling their troops that war was caused by "Jewish vermin", and explained to the troops that the war against the Soviet Union was a war to wipe out what were variously called "Jewish Bolshevik subhumans", the "Mongol hordes", the "Asiatic flood" and the "red beast".