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date: 18 January 2018

Foreign Intervention in Ethnic Conflicts

Summary and Keywords

Foreign intervention in ethnic conflicts has received significant attention in the last 20 years. Scholars have initially considered the sources for these interventions through instrumental and affective factors, though a better classification involves grouping these motives between domestic and international factors. The former category assumes that a third state’s internal politics best explain motives of intervention, and that domestic groups within the state have the greatest impact on foreign policy decision making. Theories based on domestic explanations assume that domestic politics greatly matter in the formulation of states’ decisions to intervene or not in ethnic conflicts elsewhere. As for the external explanations, scholars share a common assertion that the international environment is the central determinant explaining third state intervention. These explanations focus on the impact of institutions and international norms on the international relations of ethnic conflicts. In addition to these approaches, this area of research still contains many issues left unaddressed, such as how interference from outside might affect an ethnic conflict, and what forms of analysis might be used to study foreign interventions. Scholars have applied both quantitative and qualitative techniques, and the diaspora literature stands out for relying almost exclusively on case studies and on very notable cases. Otherwise, the rest of the work in this field follows the current standards by using a mixture of case studies and quantitative analyses depending on the questions in play.

Keywords: foreign intervention, ethnic conflicts, domestic explanations, external explanations, diaspora politics, ethnic ties, positionalism, conditionality, socialization, third state intervention


The phenomenon of foreign intervention in ethnic conflicts has gained special attention in the field of international relations in the last 20 years. This can be explained by the fact that ethnic conflicts significantly increased following the end of the Cold War (although this has since declined) and produced a greater level of interstate violence than nonethnic conflicts (Carment 1993) as exemplified by the war between Russia and Georgia in the summer of 2008. With ethnic conflicts surfacing in Europe, Africa, the Middle East, and Asia, scholars were confronted with a lack of theoretical understanding of the interconnection between these conflicts and international relations (Carment 1994). In particular, the conflicts in Yugoslavia and Rwanda sparked a greater interest in not just ethnic conflict, but the involvement of outsiders. Germany’s role in the recognition of Slovenia and Croatia (Crawford 1996) was seen by many as triggering the war in Bosnia. Both the onset of the Rwandan genocide and its impact on its neighbors, including multiple interventions in the Congo, raised many questions about the involvement of external actors in exacerbating or ending such conflicts (Kuperman 2001).

Consequently, scholars began to ask some critical questions related to foreign interventions in ethnic conflicts, such as: Why states take sides in ethnic conflicts? Why do they intervene in some conflicts but not in others? What are the motives behind these interventions? Do domestic politics or international imperatives drive this behavior? After asking why, the next question considered the effects of foreign interventions in ethnic conflicts: does external interference affect the length and intensity of ethnic conflict?

These important questions produced a bourgeoning literature on third state intervention as reflected in leading journals in international relations throughout the 1990s and 2000s. This literature made significant progress, challenging preexisting beliefs, developing stronger theoretical approaches to the questions at hand, and providing clearer evidence of the realities of intervention. The purpose of this essay is to reflect the progress made in this field of research by reviewing the recent literature on foreign intervention in ethnic conflicts.

In the first section, we define what we mean by intervention and address some of the ways in which scholars have categorized the motivations of interveners. We also consider theories focusing on the domestic sources of intervention before moving on to address those arguments focused on the international system. We conclude the section with approaches that try to integrate levels of analysis. In the second half of the essay, we focus on the effects of intervention on the onset and duration of ethnic conflicts. We also consider the methods used in this area of research, and we conclude with some suggestions for future research.

Defining the Field

Intervention is a very loose term that can apply to any kind of interplay between an outside state and the actors in an ethnic conflict. It can refer to the use of military force, economic sanctions, diplomatic involvement, offers of mediation, or even just symbolic or rhetorical support. The notion of intervention includes the idea of change – that outsiders are responding to or anticipating events within another country. This omits longstanding relationships or policies of intervention such as alliances. To provide some coherence to this discussion, we narrow our scope to focus on the most forceful forms of intervention: military assistance up to and including invasion, economic sanctions, and diplomatic recognition. We leave it for others to address the burgeoning literature on mediation (for a recent work that tests the impact of mediation, see Gurses et al. 2008) and soft forms of power and influence. Moreover, most of our focus here is on states as the primary actors getting involved in others’ ethnic conflicts. International organizations only intervene into an ethnic conflict if enough members are willing not just to vote but to send troops. There is an increased focus on such organizations as independent actors (Barnett 2002; Barnett and Finnemore 2004), but as the North Atlantic Treaty Organization has learned in Afghanistan, intervention is a state-by-state decision. Obviously, nongovernmental organizations (NGOs) become engaged in communal conflicts around the world, but again for the purpose of clarity, we restrict our focus to the actions of states. (For more on NGOs, see Bob 2005; 2007.) Finally, our focus is on ethnic conflict and not civil war. While there is much overlap between these two areas, we do omit from our discussion some of the work on involvement in civil wars if it does not speak to the ethnic dimensions of such conflicts.

Typical Typologies

Why do states intervene in foreign ethnic conflicts? For the sake of conceptual understanding, scholars have attempted to classify the motives for intervention into categories. Most of the literature divides these factors into the instrumental and affective categories. This distinction was originally made by Suhrke and Noble (1977) and has been used by many scholars since then, such as Heraclides (1990; 1991), Cooper and Berdal (1993), Carment (1993; 1994), and Ganguly (1997).

Instrumental factors refer to material considerations. Under this category, states would intervene in ethnic conflicts for expected economic gains, military power, natural resources, regional stability, or national security. This category of motives is broad and, as David Carment points out, “may relate to larger systemic, regional considerations and domestic interests” (1994:565). Indeed, this category is so broad as to become almost meaningless except that it reminds us that most approaches assume that foreign interveners are rational actors who make decisions based on self-interest.

Affective motives lead to different expectations. Rather than focusing on costs and benefits, affective arguments focus on identification with one or more of the combatants in a conflict. For instance, affective factors can refer to a common identity (culture, language, religion, ethnic ties) between a third state and one of the protagonists involved in an ethnic conflict or to considerations such as past injustice, sympathy, or common principles. Heraclides avers that instrumental motives tend to override affective considerations (1991:53).

However, scholars have questioned the relevance of the distinction between instrumental and affective factors and argued that these categories were confusing and misleading. Some have pointed out that factors that may appear affective, like ethnicity and language, can be instrumentalized as they may be used as tools for power ambition or economic gains. Hence, ethnic identification may be used by a third state as a basis for collective action and ultimately material gains. Saideman (2001), for instance, focuses on ethnic ties but in a very instrumental or utilitarian fashion. He argues that politicians often refer to ethnic politics when making foreign policy decisions to bolster domestic support and thus to increase their chance of staying in power.

We believe, therefore, that a reclassification is needed for a better understanding of the sources of intervention. We propose to set the dividing line between domestic and international factors as opposed to instrumental and affective motives. The former category assumes that a third state’s internal politics best explain motives of intervention, and that domestic groups within the state have the greatest impact on foreign policy decision making (e.g. ethnic lobbies, business community, public opinion, political regime, etc.). As for the latter, works here share a common assertion that the international environment is the central determinant explaining third state intervention (e.g. security threat, maximization of power, international norms and regimes).

Based on this reclassification of motives between domestic and international factors, the next section of this essay introduces the main explanations of foreign intervention in ethnic conflicts.

Domestic Explanations of Intervention

The following theories are generally based on liberal assumptions of international relations (Moravscik, 1997). They assume that domestic politics greatly matter in the formulation of states’ decisions to intervene or not in ethnic conflicts elsewhere. These arguments maintain that considerations such as the domestic structure of a third state or the ethnic composition of it are central factors at play.


One of the best-known theories of intervention, or rather of nonintervention, is the vulnerability thesis. According to Herbst (1989), and Jackson and Rosberg (1982) who developed the concept of the “inhibited state,” a state’s own vulnerability to internal ethnic turmoil and secessionist movements inhibits it from getting involved in foreign ethnic strife. This proposition was first tested in the African regional context and was the standard explanation during the Cold War through which third state intervention in ethnic and secessionist conflicts was studied. According to this claim, vulnerability explains why African states embrace international norms of cooperation such as the principle of non-intervention in the internal affairs of other states. The common vulnerability of African states is a strong incentive for cooperation because defection in this case would be likely to result in a dangerous domino effect, leading to the infinite redrawing of African borders. Hence, African states persist over time despite the strength of secessionist movements and ethnic tensions because leaders have no choice but to accept rules and norms of cooperation.

This straightforward and parsimonious argument was, however, strongly challenged by the academic community. Heraclides (1990) demonstrated, for instance, that multiethnic states (especially those vulnerable to separatism) are not less likely to support ethnic and secessionist movements than homogenous states. Saideman (1997; 2001; 2007) and Bélanger et al. (2005) show that the vulnerability proposition is not supported by empirical facts. Saideman indicates that vulnerable third states (including African states) are not deterred from supporting secessionist groups elsewhere. He, therefore, suggests that international norms of cooperation among vulnerable states do not account for foreign policy decision making. These studies cast serious doubt on the validity of the vulnerability proposition. Still, the vulnerability argument continues to shape perceptions, as a variety of media outlets used it to explain why some countries (such as China, Indonesia, Russia, and Spain) chose not to recognize the independence of Kosovo in early 2008, despite the fact that several of the most noted recognizers (Canada, France, Turkey, and the UK) face their own separatist challenges.

Ethnic Ties

Scholars are increasingly regarding the ethnic ties argument as a central motive for third state intervention in ethnic conflicts (Carment and James 1996; Davis and Moore 1997; Saideman 1997; 2001; 2007; Petersen 2004; Forsberg 2008). This argument has also been viewed as the main domestic challenge to the vulnerability proposition since the end of the Cold War. Saideman (2001) argues, for instance, that in an ethnic conflict, states support the side that shares ethnic ties with leaders’ constituents. Hence, when an ethnic or secessionist conflict emerges abroad, third states would support actors with which they share an ethnic kinship. Both qualitative and quantitative analyses support this argument (Saideman 1997; 2001; 2007; Carment et al. 2006; Forsberg 2008).

Others have focused less directly on the question of intervention, but have followed similar logics to consider whether ethnic ties are related to more conflict (Davis and Moore 1997; Trumbore 2003; Petersen 2004; Woodwell 2004). While the earlier work found ethnic ties or alliances to be of little influence, the latter work suggests that the existence of transnational ethnic ties can be a powerful factor shaping the likelihood of interstate conflict.

Alas, the most widely disseminated version of this argument, the clash of civilizations (Huntington 1993; 1996), is speculative rather than grounded in empirical research, and it is based on overly flexible concepts that make falsification very difficult. (For a sample of the critiques of this argument, see Henderson 1997; 1998; 2005; Henderson and Tucker 2001; and Gartzke and Gleditsch 2006). While the concept of civilization is, ultimately, elusive in Huntington’s work, it tends to come down to religion, but there are a variety of identities that may matter for domestic politics. In empirical studies of ethnic conflict, religion has been shown to be just one of several ties that may bind or divide groups.

The relevance of ethnic ties becomes even clearer when we consider two significant manifestations: diasporas and irredentism, which have been widely studied in the literature on foreign intervention in recent years.

Diaspora Politics

Ethnic ties have been taken most seriously by scholars focusing on diasporas. Here, we borrow Shain and Barth’s (2003:452) definition of diaspora, “a people with a common origin who reside, more or less on a permanent basis, outside the borders of their ethnic or religious homeland.” Diasporas can impact ethnic conflicts in two different ways: (1) they can constitute ethnic lobbies to influence the foreign policy of their host states; and/or (2) they can cause significant violence and instability in their homeland by getting directly involved in political issues.

In a study on diasporas’ impact on the Yugoslav wars of the 1990s, Hockenos (2003) explains that members of ethnic diasporas living in Western states such as Australia, Canada, and the United States, significantly contributed to the Yugoslav conflict. Albanian, Croat, and Serb diasporas were engaged in homeland conflicts through financial, political, and sometimes military support. Moreover, these ethnic groups lobbied politicians in their host countries to influence the conduct of foreign policy vis-à-vis their home countries. According to Hockenos, this sense of “exile patriotism” has flourished in Western societies since the 1990s with the disintegration of multinational states and the emergence of new communication technologies. Hockenos notes, “In the West diasporas have taken full advantage of the forums of democracy to promote homeland agendas.” Hockenos concludes that “Changing attitudes about ‘ethnic politics’ have opened new vistas for diasporas to influence international policy toward their native regions” (2003:265).

Shain and Barth (2003) formulate a theory that measures the influence of diaspora groups on the foreign policy of their homelands. They argue that diasporas are influential in democratic host states (as opposed to nondemocratic ones) and when they have an identity-based motive. The level of influence also depends on the permeability and strength of the homeland, which is the target of diaspora groups, and on the degree of cohesion in the diaspora. Based on a case study analysis of two ethnic diasporas (the Armenian and the Jewish), Shain and Barth conclude, among other things, that diasporas have a high degree of influence on weak and permeable homelands.

Several other studies have concentrated their attention on the influence of ethnic lobbies in multicultural democracies, such as the United States, where identity clearly impacts foreign policy toward ethnic conflicts abroad. Considering that the United States is the most powerful state in the current international system, its involvement in foreign ethnic conflicts is often decisive and, therefore, the influence of its diasporas may be crucial. Indeed, some argue that US ethnic groups are now a major determinant of American foreign policy (Haney and Vanderbush 1999; Nau 2002; Ambrosio 2002; Brenner and Vanderbush 2002; Shain and Cofman Wittes 2002; Hockenos 2003; Rubenzer 2008). Experts have even questioned whether US foreign policy still promotes national interest or if it has been undermined by diasporas’ interests. Shain (1999) asserted, among other things, that some ethnic groups have been able to pressure US leaders to adopt supportive policies towards national self-determination movements abroad.

In the last few years, the academic discourse about the impact of ethnic interest groups has crossed over into public debates. Most paradoxically, two scholars, Mearsheimer and Walt (2006), have taken the issue to the general public, despite the fact that their earlier work dismisses the power of domestic forces. Moreover, it is ironic that these two social scientists have been the biggest publicists for the power of diasporas, given that their research in this endeavor is lacking connections to the relevant literature. Similarly, former US National Security Advisor, Zbigniew Brzezinski, has also been concerned about the effect of ethnic lobbies. According to him, ethnic groups are increasingly powerful and have a major impact on the definition of the American national interest (Brzezinski 2006). Brzezinski believes that the academic and foreign policy communities must have a “serious debate” on this important issue.

These concerns about the power of ethnic lobbies in the United States raise a variety of issues, including whether diaspora influence is new or whether simply the white Anglo-Saxon protestant diaspora has declined in importance (DeConde 1992). More research is required to determine whether diasporas are particularly powerful in the United States, how they impact other democracies and states in transition (King and Melvin 1999), and how they impact their home countries. Thus far, the study of diasporas has been subject to much selection bias – that the most outstanding cases are examined – so what we need is more systematic analysis to determine powers and limits of transnational ethnic groups.


Events in Yugoslavia and elsewhere renewed interest in irredentism after the topic had been mostly ignored, despite the fact that it is the most direct and dangerous way in which ethnic ties can influence an ethnic conflict. To define it, irredentism involves efforts to unify one territory with another based on perceived ethnic kinship. Weiner (1971) raised a variety of questions about when a state might intervene in a neighboring state, hoping to bring back not only the ethnic kin but the land on which they reside. Brubaker (1996) referred to this as a “triadic nexus” as the outcome depends on the group in question, its host state, and its mother country or homeland. Ambrosio (2001) focuses almost entirely on an additional set of actors – the international community. He argues that aggressive nationalism within a potentially irredentist state can be contained or unleashed, depending on whether the international environment is permissive or restrictive. Others argue that domestic politics matters more (Chazan 1991; Gagnon 1994/5; Saideman 1998; Carment et al. 2006).

Indeed, Saideman and Ayres (2008) argue that when choosing between what is good for the country and what is good for the politician, leaders almost always choose the latter, even when the irredentist campaign is very likely to fail. They examine both the irredentist cases of Armenia, Croatia, and Serbia and the less violent ones of Hungary, Romania, and Russia, finding that the key is how identity shapes the interests of constituents, and that there is a limit to ethnic ties. Countries are more likely to support secessionist movements than irredentist groups not due to the fear of war (essentially inherent in irredentism) but because a successful irredentist campaign would alter the mix of people within the country, changing the balance of political power (Horowitz 1985).

Regime Type

Moving from a key source of interests to political norms, scholars have also seriously considered whether regime type influences intervention into ethnic conflicts (Bélanger et al. 2005; 2007; Saideman 2007). Adopting the logic of the democratic peace proposition, Bélanger et al. (2005) argue that democracies share political values that inhibit them from supporting each others’ secessionist movements. They assert that “a democratic regime bond between a third state and a host state constitutes an important normative explanatory variable that can account for the behaviour of foreign countries towards secessionist claims” (2005:438). Their empirical analysis shows that democracies rarely support secessionist movements in other democratic states. Their analysis also demonstrates that such an inhibition does not exist between nondemocratic regimes. Indeed, the relationship between nondemocratic states tends to increase the likelihood of assistance to secessionist groups, which shows that the normative bound is absent outside of the democratic realm. The study of the impact of democracy is an important contribution to the literature on foreign intervention. However, regime types and other political norms need further consideration, given the prominent place many scholars give to domestic interests and political processes.

External Explanations of Intervention

Most of the external arguments on foreign interventions in ethnic conflicts have been developed by scholars who espouse liberal-institutionalist or constructivist assumptions. These explanations focus on the impact of institutions and international norms on the international relations of ethnic conflicts. Realists, however, have spent most of their efforts on translating their theories to ethnic conflicts themselves – the ethnic security dilemma (Posen 1993; Rose 2000) – rather than extending their ideas to how states react to ethnic conflicts elsewhere, and testing them in this context.

Institutionalists of various stripes have been the primary international relations theorists considering the forces shaping intervention. The literature here can be divided into those works focusing on international norms and those examining European institutions and behavior.

International Regimes and Norms

Liberal arguments have built on the vulnerability thesis discussed above to argue that states often have shared interests to build regimes to govern boundaries and to discourage assistance towards separatist movements (Herbst 1989). Building upon arguments about reciprocity (Keohane 1986), Herbst argues that countries (European in the 1880s and African in the 1960s) agreed to the boundaries as they existed. Doing anything else would have risked the interests of the leaders of the time. Because most leaders in Africa in the 1960s faced serious challenges at home, they had an interest in maintaining the boundary regime which put territorial integrity ahead of selfdetermination. Zacher (2001) largely concurs with this argument.

The objective of this normative regime is to limit the circumstances under which nationalist groups have the right to independence. The regime was created around three types of norm that are not mutually exclusive but which must be understood as an international code of conduct. First, only peoples under colonial rule have the right to declare their independence by claiming self-determination. Second, states must conform to the norm of diplomatic recognition: only self-determined entities (i.e. those evolving under colonial rules) can be supported and recognized as sovereign states. Finally, the nonintervention norm forbids states from intervening in others’ internal affairs (Heraclides 1991). A third state supporting a secessionist movement that did not qualify as a self-determined unit would be intruding in the internal affairs of another state. Liberal institutionalists argue that states conform to these norms of behavior because they strengthen the structure of the international system by promoting stability, which guarantees mutual gains and cooperation among sovereign states.

This argument is different from the vulnerability argument presented previously, since it presumes that international norms rather than domestic vulnerability to ethnic conflict are the central constraint that inhibits states from intervening in intrastate conflicts. However, the expectation of both propositions is basically the same, as they both assert that states follow international norms of nonintervention. It is also interesting to note that by refuting the vulnerability argument, analysts have also demonstrated that norms of cooperation do not always inhibit states from supporting secessionist efforts (Heraclides 1990; Saideman 1997; 2001).

Conditionality and Socialization

In response to the membership processes that played out in the late 1990s and early 2000s, the study of European enlargement has become a cottage industry, and its relevance here is that scholars have argued that the membership processes helped to constrain ethnic conflict in eastern Europe during the challenging democratization processes of the 1990s. Ironically, this literature suggests that some kinds of intervention helped to inhibit other, more dangerous involvements by outsiders. This literature also serves as a battleground for the larger debate in international relations theory between rationalists and constructivists: is compliance driven by responses to threats (denied membership) or to the norms and socialization?

Kelley (2004), focusing mostly on conditionality as opposed to socialization, argues that international organizations have a positive impact on ethnic relations by linking membership admission to domestic behavior. International organizations such as the European Union (EU) and the Organization for Security and Cooperation in Europe (OSCE) are able, through reward membership, to pressure governments to introduce domestic changes such as ethnic conflict resolution in order to meet their membership standards. Kelley also maintains that it is largely through rational incentive methods that change can really occur and positively affect ethnic relations. Kelley demonstrates, for instance, that the Council of Europe (CE) and the OSCE have been able to influence states like Latvia, Estonia, Slovakia, and Romania to adopt certain legislation that eased their ethnic tensions. Vachudova (2005) makes a similar argument, although she focuses more attention on how domestic politics shaped how each country reacted to these pressures.

Linden (2000) largely concurs. He explains that, despite their history of conflicts, Romania and Hungary maintained peaceful ethnic relations following the collapse of the Communist bloc to increase their chance of becoming members of the North Atlantic Treaty Organization (NATO) and the EU. Therefore, interstate behavior conforming to international norms, as prescribed by these international organizations, would account for the surprising absence of ethnic conflict between Hungarians and Romanians since the early 1990s.

Others (Cronin 2002; Linden 2002; Checkel 2005) have focused less on the threats and inducements presented by membership processes and more on socialization – that various actors have helped to alter the norms in play and the identities of the various actors to foster cooperation and inhibit conflict. Cronin, for instance, asserts that the OSCE’s High Commissioner on National Minorities played a crucial role in teaching the new governments what was expected of European states and shaming those that fell behind. Kornprobst (2007) argues that argumentation can help to resolve disputes as justification plays a major role in facilitating conflict. Issues, when they became less justified, become easier to resolve.

Saideman and Ayres (2007; 2008), however, challenge the literature on European membership by arguing that domestic constituents’ preferences have a bigger impact on a state’s foreign policy than the external conditions set by international organizations. They raise questions about the credibility of the membership processes as countries were allowed into the European Union and into the North Atlantic Treaty Organization despite falling far short of the membership criteria. Most notably, Cyprus failed to comply with European Union integration standards but nevertheless succeeded in joining the EU because Cyprus had a strong patron in the European Union, namely Greece.

To sum up, scholars studying the membership processes of Euro-Atlantic institutions recognize the impact of international institutions and domestic politics on the course of ethnic conflict in eastern Europe, but they disagree on which level of analysis matters more and on the processes involved – conditionality, socialization, both or neither.

Defensive Positionalism

Paquin (2008) is one of the few scholars who used the realist paradigm to explain third state intervention. Built on the defensive realist work of Grieco (1988; 1990) and Mastanduno (1993), Paquin demonstrates that the United States adopts a “defensive positionalist” strategy when dealing with foreign secessionist movements. By looking at the US reaction toward Macedonia’s secession from Yugoslavia, Paquin shows that regional stability is a core US interest when dealing with foreign ethnic and secessionist conflicts. He argues that the powerful position of the USA in the international system “is maintained by the prevention of power losses that could originate from instability in the international system” (Paquin 2008:442). For this reason, the USA will not support a secessionist movement that creates instability. This explains, according to him, why the USA waited so long before recognizing Macedonia’s independence. Thus, the source of regional stability would determine upon whose behalf the USA intervenes.

Balancing and Bandwagoning

Findley and Teo (2006) have also used realist ideas to study foreign interventions in ethnic conflicts. They focus their attention on the actor-centric factors that could explain such interventions. They show that states tend to base their decisions to intervene on the realist strategy of balancing or bandwagoning, depending on the situation. Findley and Teo demonstrate, for instance, that a state is more likely to intervene on the side of the opposition if a rival state has already intervened in the conflict to support the government (2006:834). They maintain that alliance politics also plays a role in deciding which side will be supported by a state. Indeed, a state is more likely to support the government of a country in crisis if one of its allies has already intervened on the same side.

Despite the work mentioned above, the realist community has largely neglected this important dimension of international relations. One area for future research is for realists to engage the literatures discussed above and below to assess the relevance of power and security competition for the study of intervention.

Combining Levels of Analysis

Increasingly, scholars have found working at one level of analysis to be too limiting. Carment et al. (2006) develop an approach based on Robert Putnam’s Two-Level Game model. They explain that it is the interdependence between domestic and international environments that creates opportunities and constraints on decision makers as far as foreign intervention is concerned. Government leaders are the central strategic actors who make simultaneous calculations of opportunities and constraints at both the domestic and the international “bargaining tables.” They argue that institutional constraints and ethnic domestic composition are the main variables that explain the variation of third state intervention in ethnic conflicts. Thus, variations in the decision to intervene can be explained by opportunities at the internal and external levels, rather than by international norms or institutions.

Similarly, Regan (1998) develops an approach that focuses on aspects of both domestic and international politics. He starts by arguing that politicians seek to be successful, which leads him to seriously consider both domestic and international constraints. Regan argues that his decision theoretic model is influenced by both realist and liberal considerations since, as he points out, “factors attributable to both a realist and liberal understanding of world politics contribute to foreign policy decisions” (1998:764). For instance, his study shows that intense conflicts are less likely to attract outside actors (1998:754).

Clearly, one of the key steps in the next generation of scholarship on intervention is to take seriously how domestic and international forces interact to encourage or discourage states as they consider policies towards ethnic conflicts in other countries.

The Impact of Foreign Intervention

If several scholars have been interested in explaining the factors leading states to intervene in ethnic conflicts, others have been more attracted to the consequences of such interventions on the resolution of these conflicts. In the next section, we consider how interference from outside might affect an ethnic conflict. We then turn to the question of duration – does intervention shorten or lengthen ethnic conflicts?

Influencing the Course of Ethnic Politics

The possibility of intervention may play a critical role in the early stages of an ethnic conflict. Cetinyan (2002) argues that the expectations of outside involvement will shape the stances taken by ethnic groups and their host states. Jenne (2004; 2007) considers this same bargaining process between a minority in one country and its government and how it is affected by the absence or presence of a nearby homeland state. Rather than focusing on the possibility of irredentism, she focuses on whether the homeland shows significant interest and whether it has some power to pursue that interest. If so, then the group is likely to become mobilized and radicalized as it becomes confident of this outside assistance, while the host government may become more accommodating, given the group’s external ally.

Duration of the Conflict

To be clear, however, most of the work on duration has focused on civil wars in general and less so on ethnic conflict, so the review below addresses a few key examples of the former. Following a civil war, does peace last longer when there is a clear military victory or when there is a negotiated settlement? Licklider (1995) addresses this issue and attempts to identify the most effective way to end civil conflicts. As empirical evidence suggests, intrastate conflicts are difficult to end by negotiated settlement because the stakes are high most of the time and because there is a lack of institutional trust between the parties. Therefore, military victory has a positive impact on peace duration. However, Licklider notes that civil wars with an ethnic dimension are different, since military victory may lead to genocide rather than negotiation with the losing side.

Balch-Linsday and Enterline (2000) and Regan (1996; 2002) find that intervention may increase the length of civil wars if the external interference is even-handed. On the other hand, when outsiders concur and take the same side, then the conflict ends sooner. Moreover, conflicts may end sooner if the outsiders use force (Balch-Lindsay and Enterline 2000). Krain (2005), asking a somewhat different question, develops similar findings – that intervention to stop mass killings works only when the outsiders intervene against the perpertrator (usually a government).

Fortna (2004a) focuses on the impact of peacekeeping missions on the resolution of intrastate conflicts. She tries to understand whether peace is more likely to endure after civil war when peacekeepers intervene. This issue is still debated and there is no consensus on it (Doyle and Sambanis 2000; Hartzell et al. 2001). So far, the only emerging consensus is on the fact that peace is more likely to last after decisive military victory as opposed to wars that end in a tie (Toft 2003; Fortna 2004b).

By examining the impact of peacekeeping missions in the aftermath of civil wars, Fortna finds that when there is no clear winner in a conflict, there is a 50 percent chance that war will resume in the absence of peacekeepers. However, this percentage drops to one-third when there is a peacekeeping mission on the ground (Fortna 2004a). She concludes that intervention from the international community through peacekeeping clearly helps to maintain the peace and, therefore, that despite some examples of peacekeeping failures, peacekeeping makes a difference in the resolution of conflicts.

Again, the work here mostly focuses on civil wars in general, rather than ethnic conflicts. Therefore, more work should be done to determine how intervention affects different kinds of ethnic conflict. We know that secessionist civil wars last longer (Fearon 2004) than other forms of civil wars, but we do not know whether different kinds of intervention affect the various forms of ethnic conflict (secession, irredentism, coups, riots, revolutions, etc.) in similar ways or not.

Methods and Data

These issues have not been approached in one single way. In most of the areas we have discussed, scholars have applied both quantitative and qualitative techniques. The diaspora literature stands out for relying almost exclusively on case studies and on very notable cases. Otherwise, the rest of the work in this field follows the current standards by using a mixture of case studies and quantitative analyses depending on the questions in play.

This area of research poses many of the same challenges as in other areas of international studies. Focusing only on instances of intervention is problematic, but then it is hard to figure out the appropriate noninterventions to study. As mentioned above, the diaspora literature tends to focus on a few cases, but it is not clear whether these cases are typical or outliers, making it hard to figure out which dynamics apply to all diasporas.

Determining the unit of analysis is also a challenge. Focusing on each ethnic group, as the Minorities At Risk (MAR) project does as well as those that build up on it, allows us to focus on the characteristics of groups that may attract the attention of outside states, but presents challenges as well (see; for datasets that build upon MAR, see Saideman 2001; 2002; 2007; Toft 2003; Jenne 2007). Because an ethnic group’s situation may be influenced significantly by whether it has interested outsiders or not (Cetinyan 2002; Jenne 2004), it may be the case that the process of case selection (which groups are coded in the dataset and which ones are not) may be related to the dynamics we are trying to understand. More importantly for the study of intervention, MAR only has limited information about external dynamics.

International Crisis Behavior (ICB), like MAR, is based at the University of Maryland (see Brecher and Wilkenfeld 2000) but has as the unit of analysis individual cases of crises between countries. Scholars can then consider whether intervention exacerbates a dispute, but like MAR, individual scholars must add their own variables, as ICB only has limited data about intervention. Carment and James (1995) can ask whether irredentist crises are different from nonirredentist ones, using this dataset, for instance.

The Correlates of War project contains a series of datasets that have been used to study intervention. Most directly, there is the Intra-State Wars dataset (Sarkees 2000). This dataset is most useful for assessing who intervenes and for how long, but says little about the qualities of the intervener aside from its size (Balch-Lindsay and Enterline 2000). Others use the Militarized Interstate Disputes dataset (MIDs) (Ghosn et al. 2004), which allows the researcher to ask questions about what causes a dispute to escalate or not (Trumbore 2003), but again, the user must bring additional data to ask questions about intervention. The Centre for the Study of Civil War at the International Peace Research Institute, Oslo (PRIO) has several datasets that also serve as good building blocks, but need much added to them to ask questions about intervention (see Gleditsch et al. 2002).

In sum, researchers in this area have many choices, but in nearly all cases, they will have considerable work to do to supplement the datasets they choose to use.

The Future of the Field

The past two decades have seen a great deal of work and much progress made in understanding the conditions under which outsiders will get involved in an ethnic conflict and to what effect. Yet, there is still a considerable work to do. Here, we raise a few potential directions for the next decade of work on the causes and effects of intervention into ethnic conflict.

First, in most of this work, the combatants are largely seen as the objects of intervention with most of the causal weight placed on either international factors or the domestic politics of the intervening country. We need to take seriously the efforts made by the ethnic groups and governments as they try to encourage or discourage external involvement. The first efforts here have focused on how ethnic groups appeal to outsiders (Bob 2005; Saideman et al. 2005), but governments can play a role as well.

It should be clear by now that some groups gain more support than others in the same state and that a group may attract more assistance in one country than its kin in a neighboring state. Moreover, assistance varies over time, such as support for the Kurds of Iran and Iraq, but much of the work thus far tends to treat intervention more as constant. Work that focuses on timing or shifts in support may provide more insight into the forces that influence intervention.

Similarly, many ethnic groups have multiple organizations competing to represent them. While the Palestinians are the obvious case of such a group, their situation is far from unique.

We need to take seriously not only why some ethnic groups receive more support or assistance from difference sources, but also why some organizations are more or less successful in attracting outside help compared to others, despite all representing the same ethnic group.

Essentially, this is a call to take seriously the variation that exists between, among, and within ethnic groups in their strategies and their outcomes. The first generation focused the larger forces shaping patterns of intervention, but focusing on the variations may provide us with the leverage we need to determine the drivers of intervention.

Second, nearly all the work on duration – the causes of the persistence and termination of conflict – has focused on civil wars. Some attention has been paid to whether ethnic and nonethnic civil wars are distinct, but we need to do more to figure out whether intervention affects different kinds of ethnic conflict in different ways. Secessionist civil wars may last longer – is this because there is less intervention? Do ethnic revolts tend to produce overwhelming outside assistance on one side of the conflict, producing shorter conflicts? Interactions may exist between the type of conflict and the involvement of outsiders, producing shorter or longer periods of violence. As mentioned earlier, we need to take seriously whether different types of ethnic strife have distinct dynamics. If not, that would still be an important finding.

Finally, scholars are only now taking seriously how different forms of intervention may produce different kinds of outcome (Regan and Aysegul 2006). This move to taking more seriously the method of involvement may again provide us with more variation and, therefore, more leverage to understand the sources and the effects of intervention.

Of course, in suggesting these future courses of research, we do not mean to imply that the older questions have been decidedly answered. There is still plenty of debate about the sources and constraints of intervention, but considering the variations in the objects of our study – groups, organizations, assistance – may help to clarify what we have learned and what we still need to understand.


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We are thankful to the two anonymous reviewers for their constructive comments. We would like to thank Lauren Van Den Berg and Ora Szekely for their research assistance, and we are grateful to the Canada Research Chair program for funding them.