Jeremy Weinstein's Inside Rebellion is an ambitious and rewarding study of why insurgent groups vary in their structure, governance, and war-fighting. This work makes major conceptual, theoretical, and empirical contributions to our understanding of civil conflict. Weinstein's goal is to explain the level and character of the violence used by insurgent groups as their strategy for pursuing control of the central state. Strategy is disaggregated into five particular mechanisms: the recruiting base of a group, structures of internal control, governance towards the civilian population, selectiveness or indiscriminateness of violence against civilians, and resilience in the face of challenges. This conceptual breakdown of insurgent organization is a valuable contribution in its own right.

Weinstein insightfully points out that while many insurgent groups profess to follow the same ideology of guerrilla warfare, there is, in fact, huge variation in the behavior of these groups. Some wantonly kill civilians, ignore governance in favor of loot, accept all comers into the group, and lack organizational cohesion, while others engage in selective violence, carefully screen and indoctrinate prospective recruits, try to build participatory government, and respond to external challenges in a coordinated and coherent fashion.

Weinstein argues that these patterns are determined by the sources of support, or “endowments,” that rebel leaders can draw on as they attempt to launch a rebellion. His central theoretical claim is that rebels who rely on the consent of the civilian population (social endowments) for finances, recruitment, and protection from state infiltration tend to differ systematically in all of the five mechanisms under study from those rebellions that can instead draw on natural resource wealth, external support, or crime (economic endowments) as their primary source of support. These initial sources of rebel support are “sticky,” and so the endowments that underpin a rebellion tend to constrain its overall organizational structure, and thus behavior, over time.

Rebel groups that rely primarily on consensual support from the civilian population in order to wage war, Weinstein argues, tend to use selective violence, engage in participatory governance, and exhibit high degrees of discipline and organizational cohesion. These “activist” rebellions need social support for survival, and this cooperation requires that they treat civilians well. Activist insurgencies also tend to attract highly committed recruits who view their participation as an investment toward long-term political goals and are often embedded within ethnic, religious, and ideological networks that provide bonds of trust and cooperation. Due to the nature of their members, structure, and governance strategy, these organizations can maintain control and resilience even in the face of intense counterinsurgency efforts.

“Opportunistic” rebellions act very differently than activist insurgencies. They do not draw support from within the civilian population, and instead rely on economic endowments from natural resources or external political sponsorship. Opportunistic groups tend to use material incentives to draw recruits who often have little or no political commitment. The insurgent group does not need to gain the favor of civilians, so indiscriminate violence and looting by materially motivated fighters are not punished, while consensual governance is ignored. Bonds of trust and cooperation are weak, so opportunistic rebellions lack internal control and resilience in the face of challenges. These insurgencies are essentially held together by greed, rather than shared grievances or social ties, and this leads to systematically different patterns of behavior.

Weinstein uses extensive fieldwork in Mozambique, Peru, and Uganda as the primary support for his argument. The empirical comparison he lays out is straightforward—the National Resistance Army (NRA) in Uganda and national-level Sendero Luminoso (also known as “Shining Path”) in Peru both engaged in “activist” patterns of behavior, while the Mozambican National Resistance (Renamo) and a sub-faction of Sendero Luminoso engaged in “opportunistic” rebellion. He compares these four groups across each of the five mechanisms that shape insurgent behavior (recruitment, control, governance, violence, and resilience). Weinstein's empirical research is to be commended for its persuasive combination of interviews, primary and government documents, secondary sources, and quantitative data.

The case studies are used to show the power of the theoretical argument. The NRA and the national Sendero Luminoso did not have access to economic endowments like the drug trade or external government patronage. Instead, they both tapped into and established social support and attracted dedicated recruits who were willing to invest in the political project being pursued. Both groups changed local governance structures and maintained strong internal control. This pattern of behavior allowed the NRA and Sendero to survive extensive counterinsurgency efforts, and the NRA successfully seized control of Uganda, while Sendero came close to victory before its leadership was eliminated.

By contrast, Renamo in Mozambique and the faction of Sendero Luminoso based in Peru's resource-rich Upper Huallaga Valley exhibited radically different behavior. Renamo relied on Rhodesian, South African, and Western backing for its war, as well as abduction, looting, and extortion for its support. These economic endowments created a brutal and coercive war-fighting apparatus with little interest in governance or civilian consent. Indiscriminate recruiting and violence, shallow political commitment, and limited organizational adaptation all characterized Renamo's war. The faction of Sendero Luminoso based in the Upper Huallaga Valley of Peru could rely on a very different endowment than Sendero at the national level. In the Huallaga Valley, coca production provided a source of material support for this faction of the insurgency. The Huallaga Valley faction lost its ideological focus, embracing corruption, coercion, and nonpolitical violence as it increasingly relied on the drug trade for its survival.

The cases are generally compelling, as Weinstein is able to marshal detailed evidence in support of his theory. There are, nevertheless, two broad empirical issues worth noting that complicate Weinstein's argument. First, Sendero Luminoso's national organization collapsed remarkably quickly after its senior leaders were captured, despite the fact that Weinstein argues it possessed strong support in the population. It is striking, and puzzling, that Sendero's social endowments could not provide resilience in the face of leadership decapitation (unlike, for instance, Hamas). Second, while Weinstein correctly argues that Renamo relied on rigid coercive strategies, its leadership was, nevertheless, able to adapt, strategically and successfully, to external shocks. Indeed, Renamo has now transitioned into a competitive political party, despite its long history of brutality.

Weinstein also examines a set of shorter case studies to illustrate the plausibility of his argument beyond his primary cases. Though interesting, these cases tend to be more illustrative than fully persuasive. Cross-national quantitative analysis is used to show that external support for a rebel group and the presence of contraband resources both contribute to higher levels of combat-related death in civil wars since 1945. As Weinstein notes, however, these findings are also consistent with alternative explanations.

Inside Rebellion offers an original conceptualization of how insurgent organizations work that is linked to both a provocative theory and in-depth empirical research. It clearly lays the basis for future work on the organization and strategy of insurgent groups.