On Killing by LtCol Dave Grossman, 2009, Excerpts
After sixty days of continuous combat, 98 percent of all surviving soldiers will have become psychiatric casualties of one kind or another. Spending months of continuous exposure to the stresses of combat is a phenomenon found only on the battlefields of the twentieth century. Some psychiatric casualties have always been associated with war, but it was only in the twentieth century that our physical and logistical capability to sustain combat outstripped our psychological capacity to endure it. 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.
One of the things that occurs among men in combat is that they feel the high of the exhilaration stage, and then when the remorse stage sets in they believe that there must be something wrong or sick about them to have enjoyed it so intensely. It is vital that soldiers understand that this is a normal and very common response to the abnormal circumstances of combat, and they need to understand that their feelings of satisfaction at killing are a natural and fairly common aspect of combat.