It is a way soldiers impose moral order on the chaos and awful randomness of war's violence. It is a way they humanize war for themselves, for their buddies, and for civilians, too. Though Aristotle doesn't himself talk about guilt, it is the emotion that best expresses the conflict—the desire or obligation to help frustrated by the inability, through no fault of one's own, to do so. To not feel the guilt is to be numb to those pulls.