From Christopher R. Browning's "Ordinary Men": "For the most part the interrogators did not pursue this issue [anti-Semitism]. Nor were the men, for understandable reasons as potential defendants, eager to volunteer any illuminating comments. With few exceptions the whole question of anti-Semitism is marked by silence. What is clear is that the men's concern for their standing in the eyes of their comrades was not matched with by any sense of human ties with their victims. The Jews stood outside their circle of human obligation and responsibility. Such a polarization between 'us' and 'them,' between one's comrades and the enemy, is of course standard in war."

That's standard in war, but more and more also standard in our peacetime? Not all polarization leads to war, probably prewar years will be infested with polarization though, necessary to prepare a population for bloodshed and killings.

It's almost impossible to predict how individuals will behave under extreme circumstances, but what Mr. Browning's book still proves is that more or less decent men can turn into hardened killers without even much ideological enthusiasm. Peer pressure, a sense of obligation and sheer adjustment to "difficult" circumstances will do.
The same could be seen of course during the war in Yugoslavia, albeit on a lesser scale.

The first step always is to be outside the circle of human obligation.