Agent-based computational modeling (ABM, for short) is a formal and supplementary methodological approach used in international relations (IR) theory and research, based on the general ABM paradigm and computational methodology as applied to IR phenomena. ABM of such phenomena varies according to three fundamental dimensions: scale of organization—spanning foreign policy, international relations, regional systems, and global politics—as well as by geospatial and temporal scales. ABM is part of the broader complexity science paradigm, although ABMs can also be applied without complexity concepts. There have been scores of peer-reviewed publications using ABM to develop IR theory in recent years, based on earlier pioneering work in computational IR that originated in the 1960s that was pre-agent based. Main areas of theory and research using ABM in IR theory include dynamics of polity formation (politogenesis), foreign policy decision making, conflict dynamics, transnational terrorism, and environment impacts such as climate change. Enduring challenges for ABM in IR theory include learning the applicable ABM methodology itself, publishing sufficiently complete models, accumulation of knowledge, evolving new standards and methodology, and the special demands of interdisciplinary research, among others. Besides further development of main themes identified thus far, future research directions include ABM applied to IR in political interaction domains of space and cyber; new integrated models of IR dynamics across domains of land, sea, air, space, and cyber; and world order and long-range models.
Capitalist peace theory (CPT) has gained considerable attention in international relations theory and the conflict literature. Its proponents maintain that a capitalist organization of an economy pacifies states internally and externally. They portray CPT either as a complement or as a substitute to other liberal explanations such as the democratic peace thesis. They, however, disagree about the facet of capitalism that is supposed to reduce the risk of political violence. Key contributions have identified three main drivers of the capitalist peace phenomenon: the fiscal constraints that a laissez-faire regimen puts on potentially aggressive governments, the mollifying norms that a capitalist organization creates; and the increased ability of capitalist governments to signal their intentions effectively in a confrontation with an adversary. Defining capitalism narrowly through the freedom entrepreneurs enjoy domestically, this article evaluates the key causal mechanisms and empirical evidence that have been advanced in support of these competing claims. The article argues that CPT needs to be based on a narrow definition of capitalism and that it should scrutinize motives and constraints of the main actors more deeply. Future contributions to the CPT literature should also pay close attention to classic theories of capitalism, which all considered individual risk taking and the dramatic changes between booms and busts to be key constitutive features of this form of economic governance. Finally, empirical tests of the proposed causal mechanism should rely on data sets in which capitalists appear as actors and not as “structures.” If the literature takes these objections seriously, CPT could establish itself as central theory of peace and war in two respects. First, it could serve as an antidote to the theory of imperialism and other “critical” approaches that see in capitalism a source of conflict rather than of peace. Second, it could become an important complement to commercial liberalism that stresses the external openness rather than the internal freedoms as an economic cause of peace and that particularly sees trade and foreign direct investment as pacifying forces.
Caroline A. Hartzell
Civil wars typically have been terminated by a variety of means, including military victories, negotiated settlements and ceasefires, and “draws.” Three very different historical trends in the means by which civil wars have ended can be identified for the post–World War II period. A number of explanations have been developed to account for those trends, some of which focus on international factors and others on national or actor-level variables. Efforts to explain why civil wars end as they do are considered important because one of the most contested issues among political scientists who study civil wars is how “best” to end a civil war if the goal is to achieve a stable peace. Several factors have contributed to this debate, among them conflicting results produced by various studies on this topic as well as different understandings of the concepts war termination, civil war resolution, peace-building, and stable peace.
Krista E. Wiegand
Despite the decline in interstate wars, there remain dozens of interstate disputes that could erupt into diplomatic crises and evolve into military escalation. By far the most difficult interstate dispute that exists are territorial disputes, followed by maritime and river boundary disputes. These disputes are not only costly for the states involved, but also potentially dangerous for states in the region and allies of disputant states who could become entrapped in armed conflicts. Fortunately, though many disputes remain unresolved and some disputes endure for decades or more than a century, many other disputes are peacefully resolved through conflict management tools.
Understanding the factors that influence conflict management—the means by which governments decide their foreign policy strategies relating to interstate disputes and civil conflicts—is critical to policy makers and scholars interested in the peaceful resolution of such disputes. Though conflict management of territorial and maritime disputes can include a spectrum of management tools, including use of force, most conflict management tools are peaceful, involving direct bilateral negotiations between the disputant states, non-binding third party mediation, or binding legal dispute resolution. Governments most often attempt the most direct dispute resolution method, which is bilateral negotiations, but often, such negotiations break down due to uncompromising positions of the disputing states, leading governments to turn to other resolution methods. There are pros and cons of each of the dispute resolution methods and certain factors will influence the decisions that governments make about the management of their territorial and maritime disputes. Overall, the peaceful resolution of territorial and maritime disputes is an important but complicated issue for states both directly involved and indirectly affected by the persistence of such disputes.
Richard Ned Lebow
Counterfactuals seek to alter some feature or event of the pass and by means of a chain of causal logic show how the present might, or would, be different. Counterfactual inquiry—or control of counterfactual situations—is essential to any causal claim. More importantly, counterfactual thought experiments are essential, to the construction of analytical frameworks. Policymakers routinely use then by to identify problems, work their way through problems, and select responses. Good foreign-policy analysis must accordingly engage and employ counterfactuals.
There are two generic types of counterfactuals: minimal-rewrite counterfactuals and miracle counterfactuals. They have relevance when formulating propositions and probing contingency and causation. There is also a set of protocols for using both kinds of counterfactuals toward these ends, and it illustrates the uses and protocols with historical examples. Policymakers invoke counterfactuals frequently, especially with regard to foreign policy, to both choose policies and defend them to key constituencies. They use counterfactuals in a haphazard and unscientific manner, and it is important to learn more about how they think about and employ counterfactuals to understand foreign policy.
Shannon Carcelli and Erik A. Gartzke
Deterrence theory is slowly beginning to emerge from a long sleep after the Cold War, and from its theoretical origins over half a century ago. New realities have led to a diversification of deterrence in practice, as well as to new avenues for its study and empirical analysis. Three major categories of changes in the international system—new actors, new means of warfare, and new contexts—have led to corresponding changes in the way that deterrence is theorized and studied. First, the field of deterrence has broadened to include nonstate and nonnuclear actors, which has challenged scholars with new types of theories and tests. Second, cyberthreats, terrorism, and diverse nuclear force structures have led scholars to consider means in new ways. Third, the likelihood of an international crisis has shifted as a result of physical, economic, and normative changes in the costs of crisis, which had led scholars to more closely address the crisis context itself. The assumptions of classical deterrence are breaking down, in research as well as in reality. However, more work needs to be done in understanding these international changes and building successful deterrence policy. A better understanding of new modes of deterrence will aid policymakers in managing today’s threats and in preventing future deterrence failures, even as it prompts the so-called virtuous cycle of new theory and additional empirical testing.
More Than Mixed Results: What We Have Learned From Quantitative Research on the Diversionary Hypothesis
Benjamin O. Fordham
In the three decades since Jack Levy published his seminal review essay on the topic, there has been a great deal of quantitative research on the proposition that state leaders can use international conflict to enhance their political prospects at home. The findings of this work are frequently described as “mixed” or “inconsistent.” This characterization is superficially correct, but it is also misleading in some important respects. Focusing on two of Levy’s most important concerns about previous research, there has been substantial progress in our understanding of this phenomenon.
First, as Levy suggests in his essay, researchers have elaborated a range of different mechanisms linking domestic political trouble with international conflict rather than a single diversionary argument. Processes creating diversionary incentives bear a family resemblance to one another but can have different behavioral implications. Four of them are (1) in-group/out-group dynamics, (2) agenda setting, (3) leader efforts to demonstrate competence in foreign policy, and (4) efforts to blame foreign leaders or perhaps domestic minorities for problems. In addition, researchers have identified some countervailing mechanisms that may inhibit state leaders’ ability to pursue diversionary strategies, the most important of which is the possibility that potential targets may strategically avoid conflict with leaders likely to behave aggressively.
Second, research has identified scope conditions that limit the applicability of diversionary arguments, another of Levy’s concerns about the research he reviewed. Above all, diversionary uses of military force (though not other diversionary strategies) may be possible for only a narrow range of states. Though very powerful states may pursue such a strategy against a wide range of targets, the leaders of less powerful states may have this option only during fairly serious episodes of interstate hostility, such as rivalries and territorial disputes. A substantial amount of research has focused exclusively on the United States, a country that clearly has the capacity to pursue this strategy. While the findings of this work cannot be generalized to many other states, they have revealed some important nuances in the processes that create diversionary incentives. The extent to which these incentives hinge on highly specific political and institutional characteristics point to the difficulty of applying realistic diversionary arguments to a large sample of states. Research on smaller, more homogenous samples or individual states is more promising, even though it will not produce an answer to the broad question of how prevalent diversionary behavior is. As with many broad questions about political phenomena, the only correct answer may be “it depends.” Diversionary foreign policy happens, but not in the same way in every instance and not in every state in the international system.
Sabine C. Carey and Neil J. Mitchell
Pro-government militias are a prominent feature of civil wars. Governments in Colombia, Syria, and Sudan recruit irregular forces in their armed struggle against insurgents. The United States collaborated with Awakening groups to counter the insurgency in Iraq, just as colonizers used local armed groups to fight rebellions in their colonies. An emerging cross-disciplinary literature on pro-government non-state armed groups generates a variety of research questions for scholars interested in conflict, political violence, and political stability: Does the presence of such groups indicate a new type of conflict? What are the dynamics that drive governments to align with informal armed groups and that make armed groups choose to side with the government? Given the risks entailed in surrendering a monopoly of violence, is there a turning point in a conflict when governments enlist these groups? How successful are these groups? Why do governments use these non-state armed actors to shape foreign conflicts whether as insurgents or counterinsurgents abroad? Are these non-state armed actors always useful to governments or perhaps even an indicator for state failure?
We examine the demand for and supply of pro-government armed groups and the legacies that shape their role in civil wars. The enduring pattern of collaboration between governments and these armed non-state actors challenges conventional theory and the idea of an evolutionary process of the modern state consolidating the means of violence. Research on these groups and their consequences began with case studies, and these continue to yield valuable insights. More recently, survey work and cross-national quantitative research contribute to our knowledge. This mix of methods is opening new lines of inquiry for research on insurgencies and the delivery of the core public good of effective security.
Micah Dillard and Jon C.W. Pevehouse
Scholarship in international relations has taken a more quantitative turn in the past four decades. The field of foreign policy analysis was arguably the forerunner in the development and application of quantitative methodologies in international relations. From public opinion surveys to events data to experimental methods, many of the earliest uses of quantitative methodologies can be found in foreign policy analysis. On substantive questions ranging from the causes of war to the dynamics of public opinion, the analysis of data quantitatively has informed numerous debates in foreign policy analysis and international relations. Emerging quantitative methods will be useful in future efforts to analyze foreign policy.
Nazli Choucri and Gaurav Agarwal
The term lateral pressure refers to any tendency (or propensity) of states, firms, and other entities to expand their activities and exert influence and control beyond their established boundaries, whether for economic, political, military, scientific, religious, or other purposes. Framed by Robert C. North and Nazli Choucri, the theory addresses the sources and consequences of such a tendency. This chapter presents the core features—assumptions, logic, core variables, and dynamics—and summarizes the quantitative work undertaken to date. Some aspects of the theory analysis are more readily quantifiable than others. Some are consistent with conventional theory in international relations. Others are based on insights and evidence from other areas of knowledge, thus departing from tradition in potentially significant ways.
Initially applied to the causes of war, the theory focuses on the question of: Who does what, when, how, and with what consequences? The causal logic in lateral pressure theory runs from the internal drivers (i.e., the master variables that shape the profiles of states) through the intervening variables (i.e., aggregated and articulated demands given prevailing capabilities), and the outcomes often generate added complexities. To the extent that states expand their activities outside territorial boundaries, driven by a wide range of capabilities and motivations, they are likely to encounter other states similarly engaged. The intersection among spheres of influence is the first step in complex dynamics that lead to hostilities, escalation, and eventually conflict and violence.
The quantitative analysis of lateral pressure theory consists of six distinct phases. The first phase began with a large-scale, cross-national, multiple equation econometric investigation of the 45 years leading to World War I, followed by a system of simultaneous equations representing conflict dynamics among competing powers in the post–World War II era. The second phase is a detailed econometric analysis of Japan over the span of more than a century and two World Wars. The third phase of lateral pressure involves system dynamics modeling of growth and expansion of states from 1970s to the end of the 20th century and explores the use of fuzzy logic in this process. The fourth phase focuses on the state-based sources of anthropogenic greenhouse gases to endogenize the natural environment in the study of international relations. The fifth phase presents a detailed ontology of the driving variables shaping lateral pressure and their critical constituents in order to (a) frame their interconnections, (b) capture knowledge on sustainable development, (c) create knowledge management methods for the search, retrieval, and use of knowledge on sustainable development and (d) examine the use of visualization techniques for knowledge display and analysis. The sixth, and most recent, phase of lateral pressure theory and empirical analysis examines the new realities created by the construction of cyberspace and interactions with the traditional international order.