Weapon of Peace is a rigorous, multimethod test of the claim that religious liberty is a crucial component in the fight against terrorism. Saiya deploys high-quality quantitative analysis, broad-ranging case studies, and a systematically argued theory to validate this claim: religious liberty does correspond to lower levels of terrorism, while its absence results in the reverse. The book will be of interest to scholars working on religious politics and political violence, and is written in a manner that makes it accessible to those outside of academia. Its one drawback is not really a problem with the book, but rather the broader academic field: it, like many similar works, may struggle to make an impact beyond those who already think religious liberty is important.

Scholarly studies have examined the general relationship between religious liberty and political violence. Grim and Finke tested the relationship between religious repression and social religious hostilities in their book, while a slew of other scholars have conducted similar quantitative analyses (Akbaba and Taydas Reference Akbaba and Taydas2011; Basedau, Fox, Pierskalla, Struver, and Vullers Reference Basedau, Fox, Pierskalla, Struver and Vullers2017; Grim and Finke Reference Grim and Finke2011). Daniel Philpott presented a theoretical framework, which he later expanded in a book with Toft and Shah (Philpott Reference Philpott2007; Toft, Philpott, and Shah Reference Toft, Philpott and Shah2011). This author has also explored this relationship in a few works (Henne Reference Henne2012, Reference Henne2017, Reference Henne2019; Henne, Hudgins, and Shah Reference Henne, Hudgins and Shah2012; Henne and Klocek Reference Henne and Klocek2019; Kolbe and Henne Reference Kolbe and Henne2014).

What has been missing is a test of this claim that is both book-length and methodologically rigorous. Saiya’s book provides such a test. Weapon of Peace begins with an introductory chapter that explains the stakes of the book’s argument, and helpfully defines religious terrorism and religious liberty, while making a case for the importance of studying both. He then lays out his explanation for religious terrorism in the next chapter. Saiya presents what he calls a “middle ground” on the causes of religious terrorism, “that religion alone is prone neither to violence nor to peace but is instead a latent variable that becomes activated … depending on its interaction with its political environment” (30). Saiya discusses two types of religious repression, “minority discrimination” and “majority cooption.” The former leads to terrorism through three pathways, “minority backlash,” “religious outbidding,” and “vigilante terrorism,” while majority cooption can lead to “majority backlash.” Additionally, he argues that religious repression can contribute to transnational terrorism through “solicitation” and “incubation.” Saiya then discusses the way in which religious liberty can decrease terrorism, including the “marketplace of ideas,” “alternative and legitimate channels” for the expression of grievances, “peace-building activities,” and countering state authoritarianism and social extremism.

The book’s empirical analysis is spread across this chapter, as well as three chapters of case studies. Saiya presents statistical analysis on the connection between religious repression and religious terrorism, finding that the level of religious repression corresponds strongly to the number of religious terrorist attacks. He presents the details of these findings in an appendix. The three chapters of case studies examine the three aspects of his theory: minority discrimination, majority cooption, and the positive effects of religious liberty. Each includes short case studies illustrating the connection between religious liberty and religious terrorism, as well as an analysis dealing with alternative explanations. Saiya then closes with a concluding chapter that calls for an integration of and focus on religious freedom in US foreign policy.

Overall this is a solid, well-argued book. The quantitative analysis is well-done, dealing well with the tricky nature of these data. No major issues were apparent that would undermine his findings. At the same time, moving the discussion of the technical aspects of the quantitative analysis to the appendix kept the discussion moving along quickly and accessible to those not interested in quantitative methodology. The case studies were convincing, covering a variety of countries that will allay concerns that Saiya was drawing on a particular region of the world for his argument. Acknowledging alternative explanations for the level of religious terrorism, and discussing why this did not undermine his argument, was helpful. Finally, dedicating the conclusion to a policy discussion was a good way to highlight the policy relevance of this, and similar, research.

I had some minor concerns about the analysis. The most sophisticated part of the analysis was the quantitative element, while the case studies felt like more of an illustration of the statistical trends. The removal of most of the quantitative details to the appendix limited the impact of this analysis, however. And more systematic qualitative analysis of Saiya’s cases could have helped. The cases dealt with so many different contexts—for example, Pakistan’s support for militants, ethnoreligious discrimination in sub-Saharan Africa, and communal violence in India—that an expanded qualitative methods section, clarifying why these cases are comparable and the numerous confounding factors do not matter, could have been very useful. Additionally, the argument that religious repression led to religious terrorism was a lot more convincing than the one that religious liberty decreased terrorism. The latter, however, is incredibly difficult to demonstrate, so I do not see this as a major flaw.

My bigger concern had to do with the book’s implications. Numerous studies have explored the relationship between religious repression and political violence, and Saiya has investigated this in other work (Saiya Reference Saiya2017). Yet, most of the field of international relations proceeds as if this research did not exist; studies of conflict increasingly rely on overly rationalist theories that leave little room for factors such as religion, while studies of ethnic politics tend to ignore or downplay religion as an independent factor. It is not clear that Saiya’s book, as good as it is, will change this.

At some point it feels as if we are preaching to the choir (apologies for the pun). I would encourage Saiya and other scholars in this area to devote time and space in their works to making it difficult for the broader field to ignore their insights. An expanded discussion of the substantive effects—that is, how big of an impact religious repression really has—would have helped; here it is confined to an appendix. Expanded qualitative methods in the case studies, to conclusively demonstrate that religious repression cannot be ignored, would have increased the impact of these chapters. These concerns are not really the fault of Saiya’s, and do not detract from my positive opinion of this book. I just hope that scholars in this area begin thinking about how we can make sure high-quality works like Weapon of Peace receive the broad recognition they deserve.