This book asks the simple yet important question of why various countries around the world accept (and in many cases even invite) American military personnel to be based on their territory. While currently there are still some bases that the United States retains as the remnants of colonialism and invasion (such as Guantánamo Bay in Cuba), most are placed with the consent of the host state. Sebastian Schmidt makes the argument that though this setup (which has been in existence for the past 70 or so years) may seem normal to us now, it was not always the case that countries would accept others’ troops in their territory under noncoercive (or noninvasion) settings.

Schmidt’s main argument is that the concept of sovereignty has changed since the end of World War II. Whereas, in the pre–World War II era, the presence of foreign troops in a state’s territory would be considered a violation of a state’s sovereignty, the contemporary definition of sovereignty allows for “sovereign basing” (bases in which the host country’s government retains full control of their territory and the foreign troops are only there by agreement).

One of Schmidt’s important contributions is to highlight the fact that the process through which the concept of sovereignty changed, and the presence of foreign troops in a territory became acceptable, is not just one that occurred under crises. He notes that “bases might be granted for fairly trivial reasons, such as in exchange for economic considerations, or to raise revenue directly” (p. 7). Analogously, in Chapter 3 he points to the interwar example of Poland, Czechoslovakia, and France all declining to pursue military deployments from allies to deter German attacks to note that in the past there were indeed crises in which an external threat should have made it in the potential host state’s interest to allow US troops into their territory, but they did not because this would have violated their concept of sovereignty. As Schmidt notes: “The fact that sovereign basing agreements were beyond the pale of serious consideration and often did not even occur to the relevant actors” (p. 37) in a setting in which countries were facing the threat of actual invasion shows the strength of existing habits.

One way to think of Schmidt’s primary theoretical contribution is that he is explaining why there was a norm change in the international system away from foreign military bases being considered a violation of sovereignty to them being considered acceptable, even in noncrisis settings. Yet, Schmidt is clear that he uses the pragmatist term of “habits,” and not norms, intentionally. In Martha Finnemore and Kathryn Sikkink’s (“International Norm Dynamics and Political Change,” International Organization 52[4], 1998) foundational work on norm diffusion, the process through which norm entrepreneurs push for the adoption of new norms in the international system (such as women’s suffrage) is emphasized. In contrast, Schmidt notes that habits on sovereign basing did not have initial “norm entrepreneurs that instrumentalized morally laden discourse” (p. 8). In fact, under the pragmatist approach, it is not even necessary to have a clear goal in place for habits to change, as “action is rather a process, drawn out in time, through which the goals of action gradually become clearer” (p. 39). Thus, Schmidt is indeed making an original theoretical contribution by arguing that the establishment of the American military base system is not part of a grand plan, and instead emphasizing how the social interactions that take place during the basing process come to define its attributes.

Schmidt goes beyond simply presenting a theory, and instead devotes three full chapters (Chapters 4–6), to empirically examining how the US basing network with which we are familiar was established. He shows how the habit of traditional sovereignty evolved into one in which the presence of foreign troops was not seen as clashing with a state’s sovereignty. This is a key contribution that has been relevant to my own work on how interactions between deployed US servicemembers and local communities can influence perceptions of the United States and, in turn, can affect the US capacity to maintain its global basing network (see Allen et al., Beyond the Wire: US Military Deployments and Host Country Public Opinion, 2022).

In Chapter 4, Schmidt observes that because the idea of sovereign basing was indeed a new one, the US military had no real model to follow in shaping how those interactions would take place. As Schmidt notes, “It was the first time countries sought to negotiate the terms governing the long-term presence of troops on foreign territory as equals” (pp. 104–5; emphasis added). The initial tendency was for American military officers to follow the habits they had established in colonial posts, which would be inadequate in a noncolonial setting. This observation speaks to much of the work that has been written on conflict between the US military and host-country populations (see e.g., Maria Höhn and Seungsook Moon, Over There: Living with the US Military Empire from World War Two to the Present, 2010), and is a plausible explanation for the friction between military personnel and host country publics. Relations between deployed US personnel and local communities are the microfoundations of the US power projection ability and the US-led world order, so work such as Schmidt’s that better allows us to understand the context in which they occur is a much-needed contribution to the field.

While the concept of military basing is one that I believe has in the past been understudied by political scientists (who tended to see bases as simply an expression of military alliances, rather than as a political phenomenon worthy of study on their own), since the mid-2000s there have been several books that explore the question of how the US military base (and deployment) network has been established and maintained. Seminal to much of this literature is Alexander Cooley’s book Base Politics (2008), which focuses on how the domestic politics of the host country can influence the US military presence. However, Schmidt’s work is not so much focused on the cost-benefit analysis of key political players, but rather on a global change in perspectives (“habits”) regarding a foreign military presence.

This point leads to one potential criticism of the book, which is that the theory sets itself apart from rational choice approaches (see Chapter 2) by noting that it was a habit change that led to different decisions in the post–World War II era, not different cost-benefit analyses. While Schmidt makes a compelling case for the change in habits making it acceptable to establish a foreign troop presence, decisions can still be analyzed through a cost-benefit analysis once there is a change in habits. This is similar to how poliheuristic theory (Alex Mintz, “How Do Leaders Make Decisions? A Poliheuristic Perspective,” Journal of Conflict Resolution 48[1], 2004) views decisions made in two stages, with unacceptable choices being eliminated in the first stage. Habits may limit the “menu” of options, but the choice of option (the ultimate decision to host or not host, or the shape the deployment will take) can still be thought of as one made through a rational choice process (or at least can be studied as if the process is one of rational choice). A better integration of the rational choice approach into the theory would have made the book’s theoretical argument a more broadly appealing one. This is a minor criticism and one that does not diminish the merit of the book.

Perhaps the key takeaway from this book with regards to future research is Schmidt’s point that “the development of novel practices is fraught with uncertainty over what are appropriate and effective means to an end” (p. 191). The book’s empirical chapters show how much of US basing lacked a sovereign basing framework, and its development was thus not part of a grand plan but rather an endogenous process. In the concluding chapter, Schmidt goes on to discuss the potential for future basing by other major powers, such as China. Though Schmidt notes that “pragmatism has a rather pessimistic view of the capacity for prediction” (p. 215), he does make the point that US sovereign basing has now established a precedent for this process and other countries (such as China) are likely to follow the US model. The book and its theory are thus useful both in explaining how the US basing system came to be established and how the future of basing may take shape in years to come.