Recruitment is key to a terrorist group’s survival strategy. Steady enrollment is needed, not just to fight against perceived injustice, but to ultimately keep the grand strategy going. Terrorist groups depend on a continuous flow of recruits, with which they cannot survive otherwise. Moreover, weak states produce power vacuums that allow the spread of terrorist networks. This book establishes a link between weak states and terrorist actors. When a weak state fails to protect its territory and implement the rule of law because of corruption or incapacity, it results in the creation of power vacuums. Terrorist networks thrive within power vacuums and opportunistically fill the space where a weak state could not maintain control. Imitating or learning from terrorists, other political non-state actors will take the initiative to compete with the state for its monopoly on the use of violence, legitimacy, corruption and ideology. Understanding these mechanisms is key to developing strategies to combat recruitment.