Discipline is the safeguard in a warrior’s life. It is the difference between the sheepdog and the wolf. The military does not dress young troops in uniforms, shave their heads and make them march just for the fun of it. They do these things because if the young warrior cannot submit his will to authority about inconsequential things, such as the way he dresses and how he wears his hair, then he cannot be trusted to submit his will to authority for important things, such as employing deadly force only when a situation calls for it, no matter how bad the provocation.

David Grossman, On Combat, p. 230.