Powerful countries like the United States regularly employ economic sanctions as a tool for promoting their foreign policy interests. Yet this foreign policy tool has an uninspiring track record of success, with economic sanctions achieving their goals less than a third of the time they are imposed. The costs of these failed sanctions policies can be significant for the states that impose them, their targets, and the other countries they affect. Explaining economic sanctions' high failure rate therefore constitutes a vital endeavor for academics and policy-makers alike. seeks to provide this explanation, and reveals that the primary cause of this failure is third-party spoilers, or sanctions busters, who undercut sanctioning efforts by providing their targets with extensive foreign aid or sanctions-busting trade. In quantitatively and qualitatively analyzing over 60 years of U.S. economic sanctions, Bryan Early reveals that both types of third-party sanctions busters have played a major role in undermining U.S. economic sanctions. Surprisingly, his analysis also reveals that the United States' closest allies are often its sanctions' worst enemies. The book offers the first comprehensive explanation for why different types of sanctions busting occur and reveals the devastating effects it has on economic sanctions' chances of success.