The brutality of the fighting on the eastern front can not fairly be described as resulting from either Nazi ideology or the exigencies of actual combat. To make such a distinction, to borrow A.J.P. Taylor's analogy, would be to blame a car crash on the icy road, without noting that the driver was drunk, or to blame the alcohol without noting the weather.
Clearly, the underlying cause of the brutal German treatment of Russian civilians and prisoners of war must be the Nazi ideology that slavs were 'Untermensch', or lesser-humans, whose evolutionary role is to serve the 'Ubermensch', or superior-human Germans. In a setting in which the opposition and the population are viewed as a largely undifferentiated mass of bothersome, primitive throwbacks, there is little incentive not to steal from them or murder them.
The Wehrmacht made clear to its soldiers that Russians were worthy of less respect than the civilians and soldiers of the western front by enforcing a different set of policies with regard to their treatment. Specifically, German troops in France had been expected to leave the goods and women of France inviolate, while both were fair game on the eastern front. Though looting was official frowned upon, officially organized 'self-help' missions were sanctioned. The objection to looting stemmed not from any respect of the Russian peasants, rather the commanders disliked the soldiers' taking any sort of unauthorized action. Similarly, rapes on the eastern front were punished as 'racial' or 'sanitary' offenses, if at all.
Orders to the troops were explicit that certain, broad groups of the citizenry, including all Jews, partisans and Communist party officials, were to be shot. Those captured, but not killed, were to be sent back to the Einsatzgruppen, where many were killed anyway. Early in the campaign, the categories slated for immediate shooting were expanded, and by January 1942, virtually any citizen found walking about in the vicinity of the German troops could expect to be shot.
The atmosphere of hatred, in which orders had been given authorizing troops to kill huge numbers of civilian, must be understood as the crucial setting in which the battlefield atrocities took place. Soldiers in the field, with minimal respect for their opponents in any case, suffering miserably from lack of food, protection from the cold, from long hours and bombardments, would be apt to take their aggressions our on those Russians they were able to kill. Perhaps like the Americans at My Lei, a sense developed that each Russian was to blame for the grievances of every German. We should not be surprised that mass killings resulted.
from my homework for Historical Studies B-54 on October 19, 1991.