Deterrence was quickly dismissed as a possible counter-terrorism (CT) strategy after 9/11. With temporal distance from the impact, however, the concept has been given a fresh, in-depth look. The encouraging results brought the policy back to national security strategy, but today deterrence of asymmetrical threats remains largely intractable. Use of deterrence strategy, beyond the common notion of Cold War deterrence, holds promise for sustainable U.S. CT policy. The implications for U.S. foreign policy of such strategic enactments are likely more satisfactory than those employed in the first decade of the war on terror. This book seeks to explore the possibility of tailored deterrence toward the threat from radical Islamic terrorists, by gauging what is known about the strategy against what is known of the adversary, and determining the most effective path forward.