The Weapon By Oleg Volk.
Sergeant Gerheim explains that it is important for us to understand that it is our killer instinct which must be harnessed if we expect to survive in combat. Our rifle is only a tool; it is a hard heart that kills.
Our will to kill must be focused the way our rifle focuses a firing pressure of fifty thousand pounds per square inch to propel a piece of lead. If our rifles are not properly cleaned the explosion will be improperly focused and our rifles will shatter. If our killer instincts are not clean and strong, we will hesitate at the moment of truth. We will not kill. We will become dead Marines. And then we will be in a world of shit because Marines are not allowed to die without permission; we are government property .
From The Short-Timers by Gustav Hasford.