" The M16 has a scope with a small red arrow in the center of the sight. You align the arrow with what or (jeez) whom you wish to shoot and squeeze the trigger. Both “squeeze” and “pull” are exaggerations of the motion applied to this trigger. It’s a trivial, tiny movement, the twitch of a dreaming child. So quick and so effortless is it that it’s hard for me to associate it with any but the most inconsequential of acts. Flipping a page. Typing an M. Scratching an itch. Ending a life wants a little more muscle. "

― Mary Roach , Grunt: The Curious Science of Humans at War