Countries around the world increasingly impose sanctions on armed organizations – proscribing them or putting them on terrorist lists – in hopes that these sanctions will hinder terrorist activity. Does terrorist designation reduce violence? Does it achieve the intended results? Co-authors Hyeran Jo and Brian Phillips seek to address these questions in a book project. The project presents an argument about armed group adaptation, explaining how some armed groups are more financially adaptable than others, and thus better able to survive sanctions. Using case studies of groups on the U.S. Foreign Terrorist Organization list, the authors show that most armed groups have adaptable financial portfolios, and as a result, they are usually unaffected by sanctions. The findings point to the importance of understanding armed group financial adaptability, and they suggest substantial challenges for counterterrorism policy.