On April 14, 1994, two U.S. Air Force F-15 fighters accidentally shot down two U.S. Army Black Hawk Helicopters over Northern Iraq, killing all twenty-six peacekeepers on board. In response to this disaster, the complete array of military and civilian investigative and judicial procedures ran their course. After almost two years of Investigation with virtually unlimited resources, no culprit emerged and no smoking gun was found. Friendly Fire attempts to make sense of this tragedy. Lieutenant Colonel Snook, a victim of friendly fire himself, develops individual, group, organizational, and cross-level accounts of the accident and applies a rigorous analysis based on behavioral science theory to account for critical links in the causal chain of events. He offers a dynamic mechanism he calls practical drift - the slow, steady uncoupling of practice from written procedure - to complete his explanation of this tragic event.