Now, what gets to the soldiers? What is the source of stress that cripple their nerves?
Grossman starts with Fear of course. What is the source of Fear?
All soldiers face death in some form, there's always a risk of them dying and generally people don't find the thought of that too entertaining. It's widely accepted to consider the fear of death (or getting maimed) the source of psychial casualties. Simple and easy explanation.
However.
But clinical studies that tried to demonstrate that fear of death and injury are responsible for psychiatric casualties have been consistently unsuccessful. An example of such a study is Mitchell Berkun's 1958 research into the nature of psychiatric breakdown in combat. [...] The men put through the controversial — and by today's standards unethical — fear-provoking situations in these Human Resources Research Office tests were then given "long psychiatric interviews before and after and again weeks later to see whether there were any hidden effects. None were found."
Also.
The Israeli military psychologist Ben Shalit asked Israeli soldiers immediately after combat what most frightened them. The answer that he expected was "loss of life" or "injury and abandonment in the field." He was therefore surprised to discover the low emphasis on fear of bodily harm and death, and the great emphasis on "letting others down."
Very heroic answer huh - could one add with a cynical tone. But there's a continuation of this research:
Shalit conducted a similar survey of Swedish peacekeeping forces who had not had combat experience. In this instance he received the expected answer of "death and injury" as the "most frightening factor in battle. His conclusion was that combat experience decreases fear of death or injury.
Continuing:
...even in the face of a society and culture that tell the soldiers that selfish fear of death and injury should be their primary concern, it is instead the fear of not being able to meet the terrible obligations of combat that weighs most heavily on the minds of combat soldiers.
A comment on the acceptance of Fear:
How many times have we heard in movies and on television that only fools are not afraid? Such acceptance of fear is a part of modern culture.
Indeed, during World War II, in a widely distributed pamphlet entitled Army Life, the U.S. Army told its soldiers: " YOU'LL BE SCARED . Sure you'll be scared. Before you go into batlle you'll be frightened at the uncertainty, at the thought of being killed." A statistician would call that biasing the sample.