Grossman poses a question: Why do between 400,000 and 1.5 million Vietnam War veterans suffer from post-traumatic stress disorder?

In the Vietnam War, the firing rate increased to 90-95% from the 15-20% rate in World War II. This increase came at a psychological cost, especially because returning soldiers were condemned and attacked at home. New methods of training accounted for the increased firing rate. Soldiers are desensitized to killing in boot camps, as they are encouraged to chant “kill, kill, kill” (253), among other things.

Next, Pavlovian and Skinnerian conditioning is used to get soldiers to associate killing with positive reinforcements, such as merit badges and weekend passes. The soldier spends hours in a fox hole and shoots to kill targets, which look like humans, when they pop up. Since the soldier has rehearsed killing so many times, there is a sense of deniability when that soldier kills. It does not feel any different than shooting at a target.

Grossman compares the British soldiers, trained with these methods, and the Argentinian ones, who were not so trained, in the Falklands War. The British were highly effective, while the Argentinians were not. In fact, the training has been so effective that soldiers who have not killed but participated in combat nonetheless share in the guilt of killing.