Adolf Hitler Quote

The war against Russia will be such that it cannot be conducted in a knightly fashion. This struggle is one of ideologies and racial differences and will have to be conducted with unprecedented, unmerciful, and unrelenting harshness. All officers will have to rid themselves of obsolete ideologies. I know that the necessity for such means of waging war is beyond the comprehension of you generals but... I insist absolutely that my orders be executed without contradiction.

Speaking about the invasion of Russia

Operation Barbarossa: The Biggest Military Adventure in History | Mental Floss[mentalfloss.com]