In Religious Appeals in Power Politics, Peter Henne asks two significant questions: How do states use religious appeals? When and why do such appeals matter in power politics? While these questions might sound simple, they are quite complex. Maybe as complex as predicting what would happen if a “holy hand grenade [were] tossed into a crowded room” (p. 2). International Relations (IR) scholarship is far from locating the impact and conditions of religious appeals in power politics. Henne's work not only helps us understand the nature of religious appeals, but also initiates a crucial theoretical discussion on the relevance of religion in power politics. The book makes a convincing case for the importance of religious appeals without centralizing religion's impact. On the contrary, it makes room for other factors such as “material incentives” (p. 27) in understanding how and when religious appeals shape power politics. One of the key contributions of the book is the way it leans into “ambiguity” (p. 143). Rather than claiming to have all the answers, the book embraces the uncertainty and the fog around religion in IR. Henne takes the qualitative route with good reason: “The conditions I posit as giving rise to religious appeals and influencing their effects are highly context dependent. Any attempt to quantify and measure them consistently across all countries and times would be suspect” (p. 30). Both theoretically and empirically, this work contributes to the scholarship on religion and IR. With the clarity of its research design and the quality of its writing, it pulls the reader into prominent debates on the politics of faith. As always, there is room for growth. A wider angle would bring in more opportunities to locate religious appeals in different contexts. Also, a closer look at how religion relates to other sources of identity, such as ethnicity, would enhance the contribution of the study. Finally, the findings are encouraging, but they also call for further research on religious appeals.

The book starts with a well-grounded introduction. Chapter 1 sets the stage with the theoretical framework. Chapters 2, 3, and 4 include in-depth case studies: Saudi Arabia's attempt to create an Islamic Pact and its rivalry with Egypt in 1960s, the United States after 9/11 attacks with a focus on the global war on terrorism, and Russia's opposition to the West. Through these case studies, the book provides a careful consideration of religious appeals in power politics. Briefer cases in Chapter 5 expand the analysis with more context and additional examples. That chapter is particularly helpful for understanding religious appeals outside of Christianity and Islam. The Conclusion circles back to the theoretical elements of the book with a focus on key findings.

Religious appeals are described as “references to religious standards and symbols by states in official pronouncements or debates they use to justify policies or critique rivals” (p. 2). They are considered an “example of a cultural-symbolic instrument of power states can use to organize international action” (p. 3). Henne convincingly locates religious appeals in an unexplored theoretical realm. The book is critical of both security studies, which tends to ignore religion's importance, and religion in IR scholarship, which tends to centralize the role of religion in policy outcomes. I personally found this dual criticism noteworthy. While religion is no longer disregarded in IR, we are far from unlocking how it functions. One of the reasons for this limited progress is isolated perspectives on how to study religion. Henne's book makes the case for dialogue and suggests “the truth is somewhere in between” (p. 2). I couldn't agree more. The gray zone in between “religion triumphalist” who “see religion as a broadly transformative-and often beneficial-force in international relations” and “religion skeptics” who “see religion as having minimal effects” (p. 8) is home to theoretical approaches that can guide us in understanding the role of religion in IR. Religious Appeals in Power Politics aims to map out some of the pathways in this gray zone through its examination of religious appeals in foreign policy. While the book suggests religious appeals matter, it is not clear how they exactly matter. Despite not having a clear navigation system of religious appeals, the book makes a tremendous contribution to our understanding of them. Specifically, it makes the case that religious appeals can be forceful and compelling. However, they can also be unwieldy, which makes them complex tools for decision makers.

Henne does an excellent job explaining the data and methods of the book. I especially liked the way research design decisions are located in the broader scholarship. For example, the section on case selection not only explains how cases in this study are selected, it also describes how this selection relates to the rest of the scholarship. In addition, there is discussion on how such decisions influence the research process and findings. Theoretical and empirical expectations are clearly listed. Explanations are precise. Because of the descriptions, level of transparency, and quality of the design, this could be an excellent choice for an advanced undergraduate or graduate course that engages with qualitative research methods. From organization to language, each chapter successfully provides the context of religious appeals with transparency on data sources, processes, and limitations.

While the book has a global angle, it foregrounds the United States’ context and perception. One of the three cases is on the United States. The Saudi Arabia chapter engages closely with the United States as well. For example, United States’ archival records are used for the Saudi Arabia case. This is even more important due to the Cold War context of the case study. The United States considered religion as a way to counter communism. This inevitability expanded opportunities and incentives to use religious appeals. So, King Faisal's use of Islam to counter Nasser's pan-Arab foreign policy took place within that Cold War context. Looking at it through the lens of the United States makes it difficult to untangle religious appeals in this case from the bipolar ideological rivalry of its time. Having said that, Henne is forthcoming about these limitations and acknowledges how they might be shaping the outcomes.

The book also centralizes Islamic and Christian religious appeals. I found myself thinking about religious appeals in different contexts: Are religious appeals shaped by religious affiliation? Do Buddhist religious appeals and Christian ones function in similar ways? There are also unanswered questions on how religion co-exists with other identity sources such as ethnicity. What happens when there are multiple identity sources that resonate with people? How do they influence religious appeals? When they are intersecting (e.g., ethnoreligious sentiments) or working against each other, how do states use religious appeals?

Despite these limitations, Religious Appeals in Power Politics is a well-written book with a transparent research design and powerful theoretical perspective. It is a must-read for anyone who is interested in religion in IR.