During World War II, Brigadier General S.L.A. Marshall asked average soldiers how they conducted themselves in battle. Before that, it had always been assumed that the average soldier would kill in combat simply because his country and his leaders had told him to do so, and because it might be essential to defend his own life and the lives of his friends.
Marshall’s singularly unexpected discovery was that, of every hundred men along the line of fire during the combat period, an average of only 15 to 20 “would take any part with their weapons.” This was consistently true, “whether the action was spread over a day, or two days, or three.”
…Those who would not fire did not run or hide — in many cases they were willing to risk greater danger to rescue comrades, get ammunition, or run messages. They simply would not fire their weapons at the enemy, even when faced with repeated waves of banzai charges.
Why did these men fail to fire? As a historian, psychologist, and soldier, I examined this question and studied the process of killing in combat. I have realized that there was one major factor missing from the common understanding of this process, a factor that answers this question and more: the simple and demonstrable fact that there is, within most men and women, an intense resistance to killing other people. A resistance so strong that, in many circumstances, soldiers on the battlefield will die before they can overcome it.
Indeed, the study of killing by military scientists, historians, and psychologists gives us good reason to feel optimistic about human
nature, for it reveals that almost all of us are overwhelmingly reluctant to kill a member of our own species, under just about any circumstance. Yet this understanding has also propelled armies to develop sophisticated methods for overcoming our innate aversion to killing, and, as a result, we have seen a sharp increase in the magnitude and frequency of post-traumatic response among combat veterans.
Via Cracked, which is surprisingly on-point with its analysis of dehumanization in… Star Wars. Well worth the read.