From Vietnam to Afghanistan, the US sometimes fails to foster reform in host governments facing an insurgency. Why do states carrying out a large counter-insurgency operation abroad often struggle to sufficiently control their partners? Elias suggests that the key to understanding patterns in local compliance is the interaction between the respective interests and dependencies of both partners. In post-colonial civil war, the foreign intervener's ultimate objective is often to leave behind a functioning government with a minimum degree of local legitimacy. The need to empower a local partner significantly reduces the intervener's leverage: local allies, despite their weakness vis-à-vis patrons, can resist unwanted requests if they are indispensable to their execution. Allied compliance with a request from intervening partners is also unlikely when the interests of both allies converge but intervening forces can implement the request unilaterally, if necessary, due to incentives for local counterinsurgents to free ride. On the other hand, local cooperation is more likely when interests converge and the intervener is not dependent on the local partner (reducing free-riding incentives), when interests diverge but the intervener could act unilaterally (the only scenario in which the sponsor has significant leverage), and in presence of an acute enemy threat. Elias explores patterns of local compliance in five large-scale counterinsurgencies: the US in Vietnam, Iraq, and Afghanistan; the USSR in Afghanistan; and India in Sri Lanka. Using archival sources, she compiles an impressive dataset of requests from the intervening state to local partners. Why Allies Rebel provides a structural explanation for why the weak may resist the strong, generating intra-alliance tensions and potentially undermining the entire counter-insurgency endeavor.