Probably noone would deny that the job a soldier during war is pretty stressful but rarely anyone would guess that a very significant part of the casualties are psychiatric casualties.
For example:
During World War II more than 800,000 men were classified 4-F (unfit for military service) due to psychiatric reasons. Despite this effort to weed out those mentally and emotionally unfit for combat, America's armed forces lost an additional 504,000 men from the fighting effort because of psychiatric collapse — enough to man fifty divisions! At one point in World War II, psychiatric casualties were being discharged from the U.S. Army faster than new recruits were being drafted in.
Or.
In the brief 1973 Arab-Israeli War, almost a third of all Israeli casualties were due to psychiatric causes, and the same seems to have been true among the opposing Egyptian forces. In the 1982 incursion into Lebanon, Israeli psychiatric casualties were twice as high as the number of dead.
What's more:
Swank and Marchand's much-cited World War II study determined that after sixty days of continuous combat, 98 percent of all surviving soldiers will have become psychiatric casualties of one kind or another. Swank and Marchand also found a common trait among the 2 percent who are able to endure sustained combat: a predisposition toward "aggressive psychopathic personalities."
Grossman adds:
It is interesting to note that spending months of continuous exposure to the stresses of combat is a phenomenon found only on the battlefields of this century. Even the years-long sieges of previous centuries provided ample respites from combat, largely due to limitations of artillery and tactics. The actual times of personal risk were seldom more than a few hours in duration. Some psychiatric casualties have always been associated with war, but it is only in this century that our physical and logistical capability to sustain combat has completely outstripped our psychological capacity to endure it.
Humorous paraphrase:
War is an environment that will psychologically debilitate 98 percent of all who participate in it for any length of time. And the 2 percent who are not driven insane by war appear to have already been insane — aggressive psychopaths — before coming to the battlefield.