Non-state violence by rebel groups, including terrorists, has become a major headache for policy makers across the world. San-Akca’s book comes at the right time to contribute to understanding “why and how non-state armed groups emerge, endure and disappear” (p. 10). Essentially, the author investigates the motivating factors behind the unofficial cooperation between states and non-state armed groups, by using an empirical study of 355 cases of states deliberately supporting rebels, and 342 cases of rebels obtaining support by default from states during the period from 1945 to 2010.