Economic sanctions have a mixed record as a tool of statecraft. The realities of globalization and U.S. preeminence have complicated their use, even as the threats of terrorism and weapons proliferation have made them a vital instrument of national security. In this important reexamination of recent cases, O'Sullivan offers fresh insights about when and how sanctions work. She offers detailed analysis of sanctions against Iran, Iraq, Libya, and Sudan and argues that their success has hinged on a range of factors, particularly on how well a sanctions regime suits specific policy objectives; regime change, containment, and pressuring foreign-policy change each requires its own strategy. Although multilateral sanctions are desirable, O'Sullivan argues that there are still cases in which the United States might want to employ sanctions unilaterally, especially when they are only one part of a broader strategy. This shrewd book is likely to be the authoritative guide to the sanctions debate for some time.