In the Crucible, Marine recruits live out their training. With basic how-tos ingrained, they can concentrate on making crucial decisions—confident that they know what to do under which circumstances. Or at least they should. When a recruit tosses ammunition cans instead of rolling them, a drill instructor responds quickly, bending down to yell over the “Saving Private Ryan” soundtrack at the man on his back. He’s committed a serious error; a carelessly hurled 50-pound ammo can could knock out a platoon mate.