On Killing by LtCol Dave Grossman, 2009, Excerpts
There is a profound resistance to killing one’s fellow man. That the average man will not kill even at the risk of all he holds dear has been largely ignored by those who attempt to understand the psychological and sociological pressures of the battlefield. The soldier in combat resists the powerful obligation and coercion to engage in aggressive and assertive actions on the battlefield, and he dreads facing the irrational aggression and hostility embodied in the enemy. Looking another human in the eye, making an independent decision to kill him, and watching as he dies due to your action, combine to form the most basic, important, primal, and traumatic occurrences of war.
The soldier in combat is trapped within this tragic Catch-22. If he overcomes his resistance to killing and kills an enemy soldier in close combat, he will be forever burdened with blood guilt, and if he elects not to kill, then the blood guilt of his fallen comrades and the shame of his profession, nation, and cause lie upon him. He is damned if he does, and damned if he doesn’t.