While conditioning makes soldiers more efficient in the moment, it does not protect them from the aftermath. Grossman identifies several "killing response" stages, including .
To increase combat effectiveness, military training evolved to bypass this natural reluctance through behavioral conditioning.
: He posits that this aversion is a deep-seated evolutionary adaptation. Just as many animals use ritualized combat rather than lethal force against their own kind, humans have a biological "safety catch" against intraspecies killing. The Science of Overcoming Resistance
: Evidence from the Battle of Gettysburg showed that 90% of recovered muskets were still loaded—many with multiple rounds—suggesting soldiers chose to go through the motions of loading rather than actually firing to kill.
: Modern training replaced traditional bulls-eye targets with man-shaped silhouettes that pop up, forcing a "stimulus-response" action rather than a conscious moral decision.
Grossman’s analysis begins with a striking historical observation: in World War II, only about of combat soldiers actually fired their weapons at the enemy.
: Grossman notes that killing is psychologically easier when physical or emotional distance is maintained—such as through long-range artillery or the use of dehumanizing language (e.g., "collateral damage"). The Psychological Cost