A robust literature on territory in international politics—by scholars such as John Vasquez, Paul Huth, and Douglas Gibler—shows that territorial issues are much more conflict-prone than other types of issues, such as regime or policy disagreements. Toby Rider and Andrew Owsiak build on this knowledge base in their book On Dangerous Ground: A Theory of Bargaining, Border Settlement, and Rivalry. In so doing, they draw on the literatures on the bargaining model of war and international rivalry as they weave together an original and intriguing theory about border settlements.

The book is organized in a logical manner. Following an introduction in which Rider and Owsiak lay out an overview of the book and their main argument, there are three parts through which the authors develop and empirically test their argument. Part I focuses on the settlement of borders, part II explores the relationship between borders and rivalry initiation, and part III examines the connection between borders and rivalry termination. Each part contains a theoretical chapter laying out hypotheses and an empirical chapter testing those theoretical expectations through a series of quantitative analyses.

Rider and Owsiak focus on the settlement of borders between neighboring states, which is related to but distinct from a broader examination of territorial issues. Although territorial claims may come and go, only to return, the authors make a convincing argument that border settlement is permanent. As they conceptualize it, all borders are initially unsettled and only become settled after the countries sharing the border sign one or more international agreements that fully delineate their border(s). For some dyads, this happened before the authors’ data analysis begins in 1816. For many dyads, this occurred during the time period of their study, either because no agreement had been reached by 1816 or because one or both states in the dyad did not gain independence until later.

Rider and Owsiak argue that states have strong incentives to settle borders with their neighbors, both because this removes a contentious issue from their foreign policy agenda and because it allows economic activity to flourish. The bargaining model of war argues that, because conflict is costly, states should generally be able to agree, without conflict, on a way to divide a good that both prefer, unless obstacles such as incomplete information or commitment problems get in the way. Thus, borders between countries that are not plagued with information or commitment problems are quickly settled.

Information problems can lead to delays in settling borders, but conflict management techniques such as bilateral negotiations and third-party mediation can help resolve issues of incomplete information and enable states to reach a settlement, particularly when repeated. However, Rider and Owsiak argue that states facing commitment problems are in a much more difficult situation. They argue that the presence of power endowments—land that has an enhanced economic or strategic value—in the territory along the border creates a commitment problem because if the border is settled, the state that gains land will gain in power in relation to the state that loses land. This power shift creates an incentive for the gaining state to challenge the settlement in search of a more advantageous deal.

This inability to credibly commit to honoring the deal leads to tremendous difficulty for pairs of states having power endowments along their unsettled borders. Because negotiation and mediation only address information problems, they are unable to help states in these cases. The only conflict management strategies that work in the face of power endowments are legal ones, such as arbitration, adjudication, or postwar conferences. Although they do not actually prevent a power shift from occurring, these approaches do greatly increase the international audience costs of challenging the settlement because it becomes part of international law. Rider and Owsiak find strong evidence that when power endowments are not involved, each negotiation or mediation attempt increases the probability of border settlement. In contrast, when power endowments are present, negotiations and mediation have no impact on the likelihood of settlement, but each legal approach increases its probability.

Rider and Owsiak argue that pairs of states that are unable to settle their border disputes are likely to form a rivalry. They use three measures to examine each rivalry analysis. When borders are unsettled, rivalries are more likely to form, and they are even more likely when power endowments are present in the border territory. Rider and Owsiak also look at rivalry termination and find that border settlements make rivalries more likely to terminate, whereas power endowments make them less likely to do so.

Rider and Owsiak require that postcolonial states must challenge the border within one year of independence for them to be coded as unsettled. This raises the question of whether colonial legacies lead to different levels of clearly defined borders. For example, Rider and Owsiak discuss in chapter 4 and elsewhere how Spain left poorly defined borders for its former colonies in South America. Perhaps some colonizers did a better job of clearly defining borders, which would enable their former colonies to have less conflictual and more prosperous futures. Or perhaps colonial borders were poorly defined by a colonizer who controlled both sides of the border, whereas borders between colonies of different states were more likely to be clearly delineated. This is just one of many areas where the book points the way for future research.

At times, Rider and Owsiak seem to suggest that their theory is able to provide a general explanation of rivalry initiation and termination. However, their analysis is limited to only contiguous states, so they are unable to shed light on the dynamics of rivalries between states that are not neighbors, even though some of those dyads—such as the United States and the Soviet Union, Britain and Germany, or the United States and China—are among the most significant rivalries in history. Thus, although their theory certainly helps build a deeper understanding of international rivalry, it provides only part of the overall story.

These or other potential quibbles with details of the book do not detract from the significance of what Rider and Owsiak have achieved. Overall, On Dangerous Ground is a must read for anyone interested in understanding the importance of borders and territorial issues in international politics. It is also very relevant for those seeking to further explore the issues of interstate bargaining or international rivalry. The book firmly demonstrates the importance of border settlement for international politics and how unsettled borders are often connected with the formation of international rivalries.