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Article

Regime Type and Foreign Direct Investment: A Transaction Cost Economics Approach to the Debate  

Austin P. Johnson and Quan Li

A debate exists in international political economy on the relationship between regime type and foreign direct investment (FDI). The central point of contention focuses on whether multinational firms generally prefer to pursue business ventures in more democratic or autocratic countries. A considerable amount of theory has been developed on this topic; however, the arguments in previous studies lack consistency, and researchers have produced mixed empirical findings. A fundamental weakness in this literature is that while FDI has largely been treated conceptually as a homogeneous aggregate, in reality, it features divergent characteristics on multiple dimensions. Three possible dimensions that FDI can be decomposed on are: greenfield vs. brownfield, ownership type (wholly owned vs. joint venture), and horizontal vs. vertical. The most relevant dimensions to the problem at hand are: greenfield vs. brownfield, and horizontal vs. vertical. Five propositions, based on the notion of asset specificity, other investment attributes, and host nation domestic factors, are derived to predict how regime type might affect four types of FDI: vertical-greenfield; vertical-brownfield; horizontal-greenfield; and horizontal-brownfield. Depending on the type of FDI, multinational corporations may have no regime preference, an autocratic preference, or a democratic preference. This research contributes to empirical international relations theory by providing a useful example on how to resolve a scholarly debate, theoretically, and by laying out testable propositions for future empirical research.

Article

Power Transition Theory and the Essence of Revisionism  

Jonathan M. DiCicco

Power transition theory and Graham Allison’s Thucydides Trap Project are discussed in tandem with two complementary aims: to highlight theoretical and empirical contributions of the power transition research program, and to provide critical perspective on the Thucydides Trap Project. Conventional-wisdom approaches of this sort are distinguished from power transition theory, the empirical international relations theory proposed by A. F. K. Organski and further articulated and tested by generations of scholars. The theory’s central elements—national power, stages of power transition, shifts in the distribution of power, international order and the status quo—are identified and discussed, with a focus on key variables used to explain war and peace among contending states. A comparative, critical examination of the Thucydides Trap Project is used as a lens for spotlighting key empirical contributions of the power transition theory research tradition and the value of adhering to norms of scientific rigor. Opportunities for further growth and development are noted, with special attention afforded to essential features of the power transition theory research program, including the study of (1) the timing and initiation of war; (2) rising powers’ dissatisfaction with the status quo, and a possible distinction between dissatisfaction and revisionism; and (3) reducing the risk of violent, revisionist challenges.

Article

Theory of Regional War and Peace  

Benjamin Miller

The explanation of the variations in war and peace patterns across different regions, and transitions between war and peace in the same region, is based on the introduction of the state-to-nation imbalance in a certain region—this imbalance is a key substantive underlying cause of regional war propensity. Variations in this cause account for some of the major differences in the level of war and peace among different regions. Different strategies of addressing this problem (based on global or regional/domestic factors) then produce different types and levels of regional peace. The relative influence of global versus regional/domestic factors on regional war and peace is notably addressed. The study distinguishes between “hot” and “cold” (i.e., more or less intense) types of regional war and peace, and argues that global factors (i.e., the involvement of external powers) may at most bring about the less intense cold phenomena (“cold” war and “cold” peace), whereas the more demanding hot outcomes that constitute the two extremes of the regional war-peace continuum (“hot” war and “warm” peace) depend on domestic/regional causes. The key domestic/regional factors are the level of state capacity and of national congruence (both internal and external) in the region. Each of the regional outcomes is related to the combination of independent variables affecting it. This should make it possible to examine the proposed integrated effects of the state-to-nation balance and the international system on regional war and peace.

Article

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.

Article

Prospect Theory in International Relations  

Janice Gross Stein

Analysis of the use of prospect theory since the mid-1980s identifies significant impact on research on important puzzles in international security and international political economy. Research since the mid-1990s has identified the scope conditions of framing effects, loss aversion, and patterns of probability estimation on international behavior. New research using multiple methods has strengthened the validity of findings on the impact of framing effects and loss aversion under different conditions. Future research opportunities for psychological explanations of international behavior are identified.

Article

Theories of Civil War Onset: Promises and Pitfalls  

Adrian Florea

Empirical research on civil war onset has been largely dominated by two approaches: a correlational or “correlates of civil war” approach which seeks to identify country-level characteristics associated with a higher likelihood of civil war outbreak, and a bargaining approach which starts from the assumption that warfare is costly and which views civil conflict as a by-product of bargaining failures. Correlational and bargaining studies of internal conflict onset have reached an analytical plateau because they fail to specify the precise mechanisms that yield civil warfare instead of a different type of violent or nonviolent outcome. An alternative, contentious framework is advanced for studying civil war onset. This framework situates the conflict event within a larger cycle of contention and specifies the mechanisms through which civil conflict is most likely to occur. According to this contentious perspective, civil wars are commonly produced by the combination of one structural condition—a state crisis of authority and/or legitimacy—and the interdependent effect of two mechanisms—radicalization and militarization. Through theory development and vignettes from a handful of civil war cases, the article makes the case that the contentious approach holds promise for elucidating how exactly civil conflicts break out. Despite holding initial explanatory power, the contentious theory of civil war onset advanced herein awaits more systematic empirical testing.

Article

The Age-Structural Theory of State Behavior  

Richard Cincotta

Over the past three decades, economic and political demographers, using various measures, have discerned that increased age-structural maturity makes significant statistical contributions to levels of per capita income, to educational attainment, to declines in the frequency of onsets of intrastate conflict, and to the likelihood of achieving and maintaining liberal democracy. Some of the stronger statistical relationships have been used in forecasts. For example, using the United Nations Population Division (UNPD) demographic projections, political demographers have relied on the strong statistical association between age structure and stable liberal democracy to forecast the rise of democracy in North Africa more than two years in advance (in 2008)—at a time when regional experts believed that forecast to be absurd. Whereas critics remain skeptical of the murky causal connections of age-structural theory, its proponents counter that causality in the development of state capacity is complex and is less important than the theory’s positive qualities (namely, that it is forward-looking, its statistical findings are easily repeated, its forecasts have outcompeted regional experts, and its predictive products can be readily adapted to the needs of intelligence foresight, defense planning, and foreign policy analysis). Perhaps most important, the age-structural theory of state behavior has yielded a surprising number of “novel facts”—new knowledge concerning the observed pace and timing of state political, social, and economic behaviors.

Article

Peace, War, Theory, and Evidence in East Asia  

Benjamin E. Goldsmith

Historically one of the world’s most conflict-prone regions, since the Sino-Vietnamese war of 1979, East Asia has enjoyed a relative interstate peace. Implications of some of the relevant “East Asian peace” literature for theories of international relations need assessment. The central conclusion is that, contrary to often expressed dissatisfaction with the state of IR theory, it is possible to identify a core of theoretical knowledge that has considerable explanatory power for war and peace in East Asia, and is also based on general theory with considerable support across global regions. This diverges somewhat from the well-known argument of Lake in 2011: It is not the “-isms” that lead us astray, but how we use them. Unlike Lake, but consistent with Legro and Moravcsik (1999), it is argued that broad theoretical constructs are needed, and indeed useful ones exist, while mid-level or problem-focused analysis is no substitute for a theory-based research program. What is often lacking is an effort by empirical researchers to clearly and coherently tie their research design to theoretically important claims. Empirical political science as a whole is becoming more sophisticated in its methods and capabilities for causal inference, and it is also becoming more relevant and useful for policy makers. We should devote as much attention to the theoretical contributions of our research. The article addresses the role of theory in IR, the ways that empirical analysis of East Asia (and other regions) can contribute to theory building and theory testing, the existing literature on East Asian peace, some informed speculation about how the potential for mid-term military conflict between the United States and China might be assessed, and thoughts about current and potential contributions to IR theory based on the study of the East Asian peace. Theorizing in social science is hard, and any scholar’s dissatisfaction with existing theory should be heavily tempered with acknowledgment that s/he has not proposed a more powerful one. Regional analysis, and comparative regional analysis, can provide important potential gains by challenging current theory with hard tests. East Asia not only is a crucially important part of the world for the future of interstate peace, it also presents challenging and useful empirical puzzles for our theories.

Article

Power, Institutions, and Issues as Causes of Conflict  

Michael Masterson and Jessica L. P. Weeks

What do we know about the causes and outcomes of international military conflict? Decades of research from different theoretical traditions have explored the outbreak and conclusion of international conflict from a variety of angles. Broadly speaking, scholarship about international conflict has tended to orbit around three core concepts: power, institutions, and the source of the interstate dispute. The question that remains is how well verified are the most important theories? Three influential theories seek to predict patterns of international conflict: power transition theory, which argues that shifts in power increase the likelihood of war; selectorate theory, which predicts that states that have large winning coalitions are more selective about war; and theories about issue indivisibility and war, which predict that issues that states view as impossible to divide—such as a national homeland—are more likely to lead to conflict. Each of these theories produces specific predictions, allowing an assessment of how well the evidence supports the theories’ main conjectures. Central to understanding the causes of conflict is whether empirical work has tested these three theories using well-validated measures; whether a variety of scholars have tested the core propositions of the theory; and whether scholars have found evidence of the causal mechanisms proposed by each theory. Although each theory has garnered some support, they all fall short on one or more of these criteria. In particular, more work is needed in both measurement and evidence of causal mechanisms before scholars can be confident of the theories’ explanatory power.

Article

The Poliheuristic Theory of Political Decision-Making  

Alex Mintz, Steven B. Redd, and Eldad Tal-Shir

Poliheuristic theory focuses on the why and how of decision-making. The primary argument is that decision-makers are sensitive to both cognitive and environmental constraints and are particularly likely to focus on the political consequences of their decisions. Decision-makers use a two-stage process en route to choice, wherein heuristic shortcuts are implemented in the first stage in an effort to reduce complexity and in the second stage a maximizing strategy on the remaining alternatives in the choice set. The theory focuses on five main information-processing characteristics: order-sensitive, nonholistic, and dimension-based searching and noncompensatory and satisficing decision rules. The theory has been tested using numerous case studies and statistical and experimental analyses. These studies have provided strong empirical support for this theory. In 2013, the United States decided not to attack Syria, despite domestic and international pressure to do so. This case shows the importance of political constraints on President Obama’s calculus of decision, leading to the adoption of the chemical disarmament of Syria.

Article

The Theory of Lateral Pressure: Highlights of Quantification and Empirical Analysis  

Nazli Choucri

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.

Article

Akamatsu Waves  

Arno Tausch, Leonid Grinin, and Andrey Korotayev

In 1937, the Japanese economist Kaname Akamatsu discovered specific links between the rise and decline of the global peripheries. Akamatsu’s theory of development describes certain mechanisms whose working results in the narrowing of the gap between the level of development of the economy of developing and developed countries, and, thus, in the re-structuring of the relationships between the global core and the global periphery. Akamatsu developed his model on the basis of his analysis of the economic development of Japan before World War II, with a special emphasis on the development of the Japanese textile industry. Akamatsu’s catch-up development includes three phases: import of goods, organization of the production of previously imported products, and export of those goods. This model proved to be productive for analyzing the development of many other developing countries, especially in East Asia, making the theory of flying geese popular among the economists of these countries, as well as the whole world. The “flying geese” model produces certain swings that may be denoted as Akamatsu waves. Akamatsu waves may be defined as cycles (with a period ranging from 20 to 60 years) that are connected with convergence and divergence of core and periphery of the World System in a way that explains cyclical upward and downward swings (at global and national levels) in the movements of the periphery countries as they catch up with the richer ones.

Article

Women and Terrorism  

Mia Bloom

Women are playing an increasingly significant role in terrorism. As men are progressively targeted by security personnel, using female operatives provides terrorist organizations with a “win–win” scenario; if security forces avoid invasively searching women for fear of outraging the local conservative population (based on social norms of women’s modesty and the honor code), women are the ideal stealth operatives. If security personnel are too aggressive in searching women, they aid terrorist recruitment by outraging the men in that society and providing the terrorists with propaganda that “our women” are being violated. In most conflicts, women remain an untapped resource. Recruiting women allows terrorist organizations to access an additional 50% of the population. Attacks by females generate greater media attention than those conducted by men. This is especially relevant when media attention is one of the terrorists’ main objectives. Although women’s involvement in terrorist and extremist activities is not a recent development, their presence as frontline activists, propagandists, and recruiters is increasing around the globe.

Article

Civilian Self-Protection and Civilian Targeting in Armed Conflicts: Who Protects Civilians?  

Betcy Jose and Peace A. Medie

Studies have shown that civilians are often intentionally targeted in civil wars and that civilian protection efforts launched by the international community have not always been successful, if they occur at all. Civilians, therefore, have had to rely on themselves for protection in most conflicts. However, despite the pervasiveness of civilian self-protection (CSP) and its success at protecting civilians from violence in some cases, it is rarely discussed in the civilian protection literature, and its impact on civilian targeting is inadequately explored. Addressing this gap in the study and practice of civilian protection by carefully conceptualizing CSP and appreciating its role in civil war dynamics can further scholarly and practitioner discussions on civilian protection. CSP is defined as (a) actions taken to protect against immediate, direct threats to physical integrity imposed by belligerents or traditional protection actors; (b) primarily selected and employed by civilians; and (c) employed during an armed conflict. CSP strategies can be organized into three categories. The first, non-engagement, describes strategies in which civilians do not interact with belligerents or traditional protection actors who pose a threat to them. The second, nonviolent engagement, entails some interaction with one or more actors who may harm civilians. The third, violent engagement, includes CSP strategies that incorporate physical violence. These CSP strategies may actually render civilians more vulnerable to threats. First, some CSP strategies might lock civilians into unpredictable relationships with belligerents, which can become dangerous. Second, allying with one set of belligerents might lead to targeting by opposition forces, who view these CSP strategies as crucial support for their enemies. Third, civilians may overestimate how successful their CSP strategies can be, exposing them to harm. Fourth, civilian use of violence may cause belligerents to view them as threats, leading to intentional targeting. Appreciation of the reasons why civilians engage in CSP and understanding when and how this may endanger them can inspire more effective protection policies, as well as advance our understanding of civil war dynamics. For instance, further study on these issues can provide some insights into the conditions under which CSP is effective in protecting civilians and how the international community can support CSP. This information could be particularly useful in the design and execution of peacekeeping strategies that are sensitive to the efforts and needs of conflict-affected communities. Additionally, studying CSP can advance the vast literature on civilian targeting by shedding additional light on why belligerents kill civilians.

Article

War Making and the Building of State Capacity: Expanding the Bivariate Relationship  

Karen A. Rasler and William R. Thompson

A central cleavage in the war making-state making literature is between advocates of the notion that warfare has been the principal path to developing stronger states and critics who argue that the relationship no longer holds, especially in non-European contexts. It is suggested that the problem is simply one of theoretical specification. Increasingly intensive warfare, as manifested in European combat, made states stronger. Less intensive warfare, particularly common after 1945, is less likely to do so. Empirical analysis of a more representative data set on state capacity (revenues as a proportion of gross domestic product [GDP]), focusing on cases since 1870, strongly supports this point of view. The intensiveness of war is not the only factor at work—regime type and win/loss outcomes matter as well—but the relationship does not appear to be constrained by the level of development.

Article

Military Intervention in Interstate and Civil Wars: A Unified Interpretation  

Zachary C. Shirkey

Military intervention into interstate and civil wars is both common and important. It lengthens wars, makes them more severe, and shapes how they are fought. Even the mere possibility of intervention can alter the course of a war as belligerent powers alter their strategies to either encourage or dissuade potential interveners. These effects of military intervention are found in both civil and interstate wars. Yet, is state intervention into interstate and civil wars essentially one phenomenon or are they distinct phenomena? By looking at which states are likely to intervene, why and when they intervene, and which wars are most likely to experience intervention, it becomes clear the similarities between state military intervention into civil and interstate wars are more significant than are the differences. In other words, despite some important differences, they are subsets of the same phenomenon. In both types of wars, allies, geographically proximate states, and great powers are more likely to intervene. Also, information revealed by events within both types of wars prompts intervention and explains its timing. Last, wars in which international organizations become involved, both civil and interstate, are more likely to experience intervention. There are, however, important differences notably in the areas of cross-border ethnic ties, the presence of great powers in the war, the use of non-state proxies, and wars caused by commitment problems.

Article

National Secession  

Philip G. Roeder

National secession seeks to create a new sovereign state for a nation residing on its homeland that is currently located inside another sovereign state. This goal distinguishes national secession from regional secession, autonomy, and decolonization and shapes the strategies, operational objectives, and tactical choices of the leaders of national-secession campaigns. Explanations for the success of some campaigns—particularly, success at getting on the global agenda—have focused on the identities, grievances, or greed of their members. Explanations for why some campaigns have turned to protracted intense violence have focused on these motivations and on tactical-logistical opportunities. The existing literature suffers from its failure to agree on theoretical and conceptual fundamentals. As a consequence, empirical studies focus on very different universes of cases and operationalize key variables in diverging ways. The existing literature frequently does not consider how the goal of national secession constrains the strategies, operations, and tactics of such campaigns. And so, it often fails to consider whether studies with another dependent variable can be extended to the study of national secession. Explanations stress indeterminate or substitutable causes and remote constraints on most national-secession campaigns—causes and constraints taken “off the shelf” from theories about conflicts operating under very different strategic and operational constraints. Missing from these explanations is the authenticity and realism of the programs for national secession in the assessments of the populations that each program presents as a nation with a right to a sovereign state of its own. Explanations and recommendations for responses by common-state governments, their allies, and the international community often fail to understand the centrality of the war of programs between national secessionists and common-state governments and the ways this constrains what compromises are possible and what responses are most likely to lead to domestic and international peace in such conflicts.

Article

Defining and Operationalizing Context Through a Structural Political Geography for International Relations  

Colin Flint and Raymond J. Dezzani

A structural understanding of the contextualized behavior of states is introduced and operationalized. Context is a central theme of the discipline of geography and identifies context specific, rather than universal, social behavior. Social behavior is both defined by and creates contexts in a constant recursive interaction. Context is defined through a geographic perspective on world-systems analysis, and we focus on the behavior of states. States are central actors because, through territorial sovereignty, they are able to define key social relations and economic flows. The idea of context is developed in a way that extends the key International Relations (IR) concepts of milieu and opportunity and willingness. The recursive interaction between agency and context is conceptualized in a relational way as maneuver, the process by which the aggregate behavior of elites define state-level choices and behaviors that are made by considering the contextual position relative to all other states in the capitalist world-economy. In turn, the decision by any one state changes the behavior of other states so that context and state-level decisions interact and are constantly in flux. The elements of context include the position of a state in the hierarchy of the capitalist world-economy as well as regional and local interstate relations, some of which may display path dependency. The operationalization of maneuver requires an understanding of states as signaling and learning entities and a set of modeling techniques that identify: (1) the degree of change within the system as a whole—or the degree of stability in the number and identity of states within particular positions in the hierarchy of the capitalist world-economy; (2) the maneuver of particular states—or which states change position (or not) within the hierarchy; and (3) the explanatory power of variables measuring political and economic interstate relations in explaining the maneuver behavior of particular states.

Article

Hegemony, Hierarchy, and Unipolarity: Theoretical and Empirical Foundations of Hegemonic Order Studies  

Carla Norrlof

Scholars of international political economy in the 1970s explored the relationship among a dominant power, leadership, and openness. The discussion soon centered on the concept of hegemony, meaning a situation in which a single state exercises leadership in creating and maintaining the fundamental rules of the international system. The scholarly arguments that ensued focused on the rationale for, and durability of, hegemony, and seemed relevant because of a shared assumption that U.S. dominance, so strong during the quarter-century after World War II, was declining. However, the debate was premised on a shared but incorrect empirical perception that American hegemony was declining. When similar questions arose again at the end of the 20th century, the terminology used was less that of hegemony than of unipolarity and hierarchy, and the key question was whether exercising continuing leadership would be so costly to the hegemon that its decline would be generated by its leadership. The issues of hegemony raised in this literature have taken on renewed relevance with the election of Donald J. Trump as President of the United States.

Article

Effectiveness of Peacekeeping Operations  

Jessica Di Salvatore and Andrea Ruggeri

Peacekeeping has been one of the main conflict management tools used by the international community to restore or safeguard peace and security. Since 1948, the United Nations has established 70 peace operations and has substantially evolved, adopting approaches to peace that extend beyond purely military concerns. Indeed, the promises of peacekeeping as effective instrument of conflict reduction may, to some extent, explain the evolution toward multidimensional missions and the unprecedented number of peacekeepers deployed in the last decade. As consequence, the growing importance of peacekeeping effectiveness has sparked a new wave of research that empirically investigates whether and under which conditions UN peacekeeping works. Peacekeepers are mostly deployed in conflict or postconflict environments where violence is either ongoing or lingering. Thus, violence remains a priority for peace missions. Consequently, peacekeeping is deemed successful or effective according to whether it curbs conflict in several dimensions. Effective missions are those responsible for decreasing the intensity of battle violence, protecting civilians, and containing conflict diffusion and recurrence in the postwar phase. Each mission, however, is deployed in different contexts and operates under variable conditions that affect the operation’s capacity to influence conflict. Concerning mission features, peacekeeping success is more likely when large contingents are deployed under robust mandates. Mission type, size, and composition signal credible commitment from the international community and empower peacekeepers to halt violence while guaranteeing the implementation of peace agreements. These nuanced understandings of peacekeeping stem from the availability of new data on both conflict and peace operations at the national and subnational levels of analysis. Moreover, the empirical study of the effectiveness of peace operations has recently been flanked by simulation-based forecasting, field experiments, and surveys investigating local-level outcomes of peace missions. Unsurprisingly, the focus on violence and conflict outcomes as indicators of success is debatable. First, in dealing with violence, peacekeeping operations produce spillover effects that are largely neglected, such as refugee flows and terrorist violence. Second, given the wide range of functions performed by UN peacekeepers, including electoral assistance, economic reconstruction, and state building, it is reasonable to include these aspects when defining effectiveness. Third, and relatedly, no assessment of short- versus long-term implications of peacekeeping for political, social, and economic development in the host country has been forthcoming. While reducing infant mortality, inequality, and crime are not necessarily tasks for peacekeepers, it is vital to study whether and how UN missions may have shaped the quality of peace in host countries.