How do civilians control the military? In the wake of September 11, the renewed presence of national security in everyday life has made this question all the more pressing. In this book, Peter Feaver proposes an ambitious new theory that treats civil-military relations as a principal-agent relationship, with the civilian executive monitoring the actions of military agents, the "armed servants" of the nationstate. Military obedience is not automatic but depends on strategic calculations of whether civilians will catch and punish misbehavior.