That's the most horrible thing we learned during the 20th century. That kind of atrocities haven't been perpetrated by 'monsters', 'psychopath' or however we could depict the authors to remove their humanity. They have been done by 'us', normal human, people who thought of themselves as good persons and thought they were fighting for a good cause and doing the right thing.

They way you do it is little by little. You first makes the person feel entitled, you give him reasons to hate the 'enemy', you remove accountability of the executant by using a strict hierarchy and by engineering the killing process. At one point it becomes 'normal' and 'logic' to do what you do.

Thats a great way of describing the process of creating an enemy, the question is what you do with that enemy. Natzy Germany took it to the extreme of total extermination. I can't help but notice how this is still a very effective tactic that governments, in particular in the west, continue to use to advance its military agenda - we just haven't got to the point of were we see another full blown extermination in progress. However, and the scariest part of this is that all the machinery to achieve that is in place and has only improved. The media (willingly or unwillingly) is very effective at painting an enemy, dehumanizing him and eventually justifying military action. Can this be changed, is there a way of doing the right thing, without abusing it?

The banality of evil.

https://en.wikipedia.org/wiki/Adolf_Eichmann

Almost everyone would react the way you describe-- the first time. But people are resilient. Expose them to enough atrocity, and if they survive, the horror of it will fade until it becomes a prosaic fact of life. We see it in soldiers. We see it in EMTs.

The coping mechanisms are not perfect. What we now call PTSD has and will continue to destroy lives long after the fighting is over. But they do allow for continued functioning in the field. For better or for worse.

In fact, it was rather draining. The Einsatzgruppen - SS task forces that manually machine-gunned people (mostly Jews) during the invasion of the Soviet Union, including at Babi Yar - were disbanded fairly early in the war because of mental health problems among the staff. One of the main motivations of the characteristically "industrial" methods of the later Holocaust - first gassing trucks, then gas chambers and starvation - was to reduce the exposure of SS personnel to the act of killing, even when they were aware of and enthusiastic about their mission.

Source: "The Third Reich At War", by Richard J. Evans.

The key, as it has always been through the centuries, is to not think of whoever you're killing as "people". Yes, they slaughtered thousands of people like pigs, because they didn't view them very differently from pigs.

Turns out, in addition to our evolved horror of killing someone like ourselves we also have an evolved ability to dehumanize the other to the point where the "someone like ourselves" label no longer applies. Came in pretty handy, evolutionarily speaking, when two packs of monkeys ended up in close proximity, with insufficient food.

Different people react differently. The first dead I saw was a women, falling to her death from the 9th floor. I was 3 at the time and there was no revulsion, just curiosity I guess. Maybe just because I didn't have enough of understanding of 'death' at that time.

I've seen people die (or dead already) many times since then and... It doesn't really make you sick. The unpleasant feeling is still there, yes, but it's more about disgust than anything else.

Methamphetamine