Why are some anti-base movements successful? In Activists, Alliances, and Anti-U.S. Base Protests, Andrew Yeo argues that much of the variation in the success of protest movements at changing U.S. basing around the world hinges on the “security consensus” of political officials within the host government. When key players in the host country are united in their view that a U.S. military base on their soil is necessary for political-strategic reasons, anti-base protest movements can, at best, achieve only minimal concessions from the host government. Conversely, when key players in the host government are divided as to the strategic importance of the U.S. base, anti-protest activists then have a powerful political opportunity structure through which to demand drastic changes in line with their movement goals. By showing how the nature of the security consensus serves as a key political opportunity structure for activists, Yeo adds powerfully to our understanding of the potential role of non-state actors in very realpolitik foreign-policy situations. In short, much of the potential success of activists depends on the preexisting social and political context: If the base is seen as vitally important for security, it is unlikely that even well-established activist movements will be successful.

This book contributes in many ways both to general international relations scholarship and to more cross-disciplinary work on social movements. First, much scholarship on international and domestic activist movements centers on the ways in which activists spread fairly new international norms, like human rights or environmental protection (e.g., see Margaret E. Keck and Kathryn Sikkink, Activists Beyond Borders: Advocacy Networks in International Politics, 1998). Yeo's study, however, concerns advocacy related to established norms of sovereignty and international security. This focus provides those in the advocacy network tradition with a fascinating set of case studies that have traditionally been missed, drawing attention to variables, like alliance patterns and international threat perception, that are typically not the theoretical focus in more traditional work. Likewise, for international relations scholars more steeped in the realist tradition, this work highlights how nonstate actors can be key movers in shaping policy decisions concerning international security.

For those in the social movement tradition, the book also reinforces how critical political opportunity structures are for movement success. Unlike traditional work, however, the book does not argue that the key political opportunity structure for anti-base advocacy is institutional. Instead, Yeo's theory of the importance of the security consensus highlights how political opportunity structures can be completely ideational: What matters is variations in the intersubjective understandings of the importance of the U.S. base for national security, irrespective of regime type. In fact, as Yeo points out, some earlier work on the importance of host-country regime type for U.S. basing strategy can be “subsumed” (p. 183) into his theory on the role of a strong security consensus within a host country (e.g, see Alexander Cooley, Base Politics: Democratic Change and the U.S. Military Overseas, 2008).

Worth noting, however, is that Yeo's theory does not contend that a weak security consensus necessarily translates into movement success. Rather, the weak security consensus serves as an advantageous window through which advocates may be able to influence policy. Without this weakened security consensus, advocates are more likely to just receive “token concessions” (p. 26), something akin to the focus of earlier human rights advocacy network scholarship on “tactical concessions” (e.g., see Thomas Risse, Stephen Ropp, and Kathryn Sikkink, eds., The Persistent Power of Human Rights: From Commitment to Compliance, 2013), where regime leaders often try to pacify advocates with limited policy changes. Similarly, as Yeo argues, when there is a strong security consensus, the targeted state may try to limit the strength of the movement through repression.

Unlike the typical international relations focus on the country/year, Yeo tests his theoretical framework in a series of case studies at the “movement episode” (p. 30) level of analysis in the post-Cold War period. Each movement episode concerns a U.S. base within a particular host country. Given the preeminence of the U.S. military during this time period, the focus on only U.S. bases makes it more likely, one could argue, that none of the movements would be successful. Instead, as Yeo's detailed process tracing shows, activists were successful in many different cases, including in the Philippines with the closure of the Subic Bay Naval Station in 1991 and with the closure of the U.S base in Manta, Ecuador, in 2007. Other cases examined by the author had a much stronger security consensus that worked to limit even vibrant and tenacious advocacy attempts, such as the advocacy over the expansion of Camp Humphreys in South Korea in 2005; the presence of the U.S. Futenma Air Base on Okinawa, Japan, in 1995–96; and the expansion of Camp Ederle in Vicenza, Italy. Although Yeo argues that the nature of the security consensus is pretty “sticky” (p. 151) over time, he does point out that the post-9/11 international security environment and alliance patterns in the Philippines have worked to strengthen the security consensus concerning the necessity of a U.S. military presence in that state, limiting recent advocacy movement success. He also points out that recent changes in Japan could herald a future weakening of the security consensus in Japan concerning Okinawa.

Activists, Alliances, and Anti-U.S. Base Protests provides much that future scholarship could build upon. Future work could focus specifically on whether or not advocates can have a long-term impact on the security consensus. Could early advocacy that is not successful still provide doubts in the minds of policymakers that would help later advocates? Future work on Okinawa, in particular, could look at these more long-term cross-movement dynamics. Further, future work could focus on learning among activists themselves. Why do rational activists still pursue costly movements in the face of a strong security consensus? Are activists less likely to even stage protests in South Korea today, knowing that such a strong security consensus limited their movement success in 2005–6? Is the international advocacy network that is concerned with U.S. basing decisions, like transitional-justice and human-rights international nongovernmental organizations, now learning which cases to devote resources to, based on the role of the security consensus in previous advocacy attempts? Future work on these questions would go far in joining Yeo's theory with other influential works on issue adoption (e.g., Clifford Bob, The Marketing of Rebellion: Insurgents, Media, and International Activism, 2005).

In short, Yeo's masterful study offers much to scholars of international relations and social movements. At the most general level, it speaks to long-standing questions of the role of ideas and nonstate actors in critical security situations (e.g., see Kenneth Waltz, Theory in International Politics, 1979). For those interested pragmatically in U.S. basing policies, Activists, Alliances shows how anti-base movements can potentially disrupt foreign policy, especially if the weak security consensus in host countries creates political opportunity structures that provide the “spark” for advocated change.