On Killing: The Psychological Cost of Learning to Kill in War and Society is a book by Dave Grossman exploring the psychology of the act of killing, and the military and law enforcement establishments' attempt to understand and deal with the consequences of killing. The book is based on S.L.A. Marshall's theory that the majority of soldiers in war do not ever fire their weapons due to an innate resistance to killing. Overview The book is based on S.L.A. Marshall's studies from World War II, which proposed that, contrary to popular perception, the majority of soldiers in war do not ever fire their weapons because of innate resistance to killing. Based on Marshall's studies, the military instituted training measures to break down this resistance, raising soldiers' firing rates to over 90 percent during the Vietnam War. Grossman points out that there are great psychological costs that weigh heavily on the combat soldier or police officer who kill if they are not mentally prepared for what may happen; if their actions (killing) are not supported by their commanders and/or peers; and if they are unable to justify their actions (or if no one else justifies the actions for them). The second edition of the book, along with an audio version, was released in 2009. The soldier's choice Grossman claims in his book On Killing that soldiers are faced with four options once they have entered into combat. Fight: As the name implies, this is the standard that defines the soldier’s role as actively trying to defeat the enemy by use of their training. Flight: This option involves the combatant fleeing the engagement. Posture: This action involves the soldier falsely showing active participation in combat. In actuality they are not being effective in deterring the enemy from success. This is a major point of concern for commanders as it is difficult to tell the difference between a soldier posturing or fighting. Submit: Submission to the enemy during an engagement is a direct act of surrender. In the animal kingdom, this is used by lesser combatants to avoid being injured upon ascertaining the futility of the battle. The problem of non- or miss-firing soldiers S.L.A. Marshall did a study on the firing rates of soldiers in World War II. He found that the ratio of rounds fired vs. hits was low; he also noted that the majority of soldiers were not aiming to