Jiyoung Ko, Kathleen E. Powers 2024
Does nationalism increase the probability of international conflict? An affirmative answer has intuitive appeal: Nationalists promote force to protect their land and people from foreign threats. Research on nationalism in international conflict implicates elites, masses, and political interactions between these actors when asserting its status as a powerful force that raises the risk for interstate wars. Yet both micro- and macro-level evidence cautions against drawing broad conclusions about how nationalism affects conflict. Nationalism sometimes prompts aggression. In other contexts, nationalism produces restraint. Systematic knowledge about how nationalism relates to international conflict therefore requires answers to questions about which nationalisms promote conflict and whose nationalism matters.
This article first reviews theory and evidence about nationalism’s conflict-causing potential. We discuss the microfoundations that link nationalism to foreign policy attitudes before describing research that implicates nationalism as a cause of militarized conflict. Next, we argue that understanding the complex relationships between nationalism and conflict requires theorizing the causal processes that connect various stakeholders’ nationalism to foreign policy outcomes. Moreover, research on identity content suggests that nationalism is compatible with a variety of foreign policy preferences. Throughout, we center research that features nationalism as a principal independent variable or causal mechanism precipitating conflict.1Of course, rally effects and related phenomena suggest that nationalism is partly endogenous to war (Mueller 1973).
Any review about nationalism must contend with the delicate matter of conceptualization — the field contains nearly as many definitions for nationalism as articles about nationalism and war (see Mylonas & Kuo 2017 and Bonikowski 2016 for helpful discussions). The research we discuss variously describes nationalism as an identity, ideology, or belief, for example. For our purposes, nationalism captures a set of sentiments related to a national group and its superiority. This broad perspective centers the phenomenon implicated in international conflict research.
Microfoundations: Nationalism and foreign policy attitudes
One research program tackles questions about nationalism and conflict from the bottom-up, examining the psychological foundations that connect beliefs about the nation to militaristic attitudes and policy preferences. Evidence that determines whether nationalism creates foreign policy hawks is important for at least two reasons. First, it provides insights into the psychology of foreign policy attitudes, explaining why nationalism might mobilize elites and citizens toward war. Second, if nationalism generates militarism, tracking public nationalism provides a leading indicator for future conflict support (Johnston 2017, though cf. Weiss 2019). Research connecting individual or mass public nationalism to militarism informs macrolevel claims that nationalist surges raise the risk for war.
Arguments linking nationalism to militarism use psychology to explain how beliefs about national superiority cause people to inflate threats from foreign countries. Humans categorize themselves and others into social groups (Tajfel & Turner 1979), favor fellow group members, and feel good when their group succeeds. Although people can endorse “in-group love” without “out-group hate” (Brewer 1999), asserting national superiority implies competition (Kosterman & Feshbach 1989) and boosts self-esteem (Branscombe & Wann 1994). In turn, nationalists believe in the group’s moral righteousness, preserve resources for their own group, and strive to advance the group’s status. Nationalism biases views about outsiders, leading people to perceive adversaries as hostile and having malign intentions (Herrmann 2017; Cottam & Cottam 2001). These beliefs facilitate aggression, insofar as people desire domination over others or believe that protecting their own country requires force. Notably, this micro-level research expects variation between individuals. The psychological mechanisms that predict conflict support apply among citizens who express strong nationalism, not those weakly committed to their national group’s superiority.
Individual-level research often distinguishes nationalism from related views about national in-groups. Scholars use nationalism, national chauvinism, or similar terms to denote the set of beliefs and identities that cause threat inflation and conflict, treating patriotism, attachment, or identification as separate phenomena.2See e.g., Druckman (1994), Huddy and Khatib (2007) Gries et al. (2011), and Herrmann, Isernia, and Segatti (2009) for arguments distinguishing nationalism from related attitudes about the nation (cf. Bonikowski 2016). This review centers the former. We use “nationalism” to capture those sentiments presumed to cause militarism and identify cognate concepts where appropriate.
Substantial research shows that nationalism correlates with public support for conflict. Surveys gauge nationalism using an impressive array of indicators that capture beliefs about national superiority — via sentiments about international sports victories, whether the world would be better off if the respondents’ home country had greater influence, and whether the home country is generally superior to others (Hurwitz & Peffley 1987; Kosterman & Feshbach 1989; Druckman 1994; De Figueiredo & Elkins 2003; Kemmelmeier & Winter 2008; Herrmann, Isernia & Segatti 2009). Individual scores on the resulting nationalism scales correlate with support for force and antipathy toward foreign countries (Hurwitz & Peffley 1987). For example, Herrmann, Isernia and Segatti (2009) find that nationalism predicts militarist dispositions and decreases support for appeasing adversaries in both the U.S. and Italy. Federico, Golec and Dial (2005) conclude that nationalists support military action against Iraq. Scholars observe similar patterns in non-western countries. Gries et al. (2011) find that Chinese nationalism correlates with higher perceived threats from the U.S. and support for a tougher U.S. policy, for example, and nationalism correlates with hawkish foreign policy preferences in a South Korean student sample (Bliss, Oh & Williams 2007). Ko (2022) demonstrates that invoking historical animosity toward Japan raises both Chinese nationalism and public support for hawkish responses to a Sino-Japanese territorial dispute. Evidence showing the inverse relationship also makes the case for nationalism’s hawkish orientation: For instance, humiliating military defeats threaten national superiority and increase conflict support as people recoup their psychological loss with assertive foreign policy preferences (Barnhart 2020; Masterson 2022).
The same tendencies will manifest among elites if arguments about nationalism’s microfoundations generalize. Nationalist leaders should inflate threats (Walt 1996), promote myths about their country’s virtues (Van Evera 1994), and choose aggression against adversaries. But researching elite nationalism creates several new challenges for deducing its relationship to conflict. First, we lack significant survey research among heads-of-state. Public statements or speeches with nationalist content provide an alternative method for assessing whether a leader holds nationalist beliefs. But speech data raise a second challenge: Leaders may also use nationalist language to signal commitments to domestic or international audiences, confounding claims that their nationalist views cause conflictual orientations.
Research using related psychological concepts and employing at-a-distance measures nevertheless reach similar conclusions to those of public opinion scholars. Nationalist elites endorse more aggressive foreign policy approaches. Hermann’s (1980) leadership trait analysis framework argues that leaders with high scores on “in-group bias” and “distrust of others” take active, hawkish foreign policy approaches. Such leaders inflate their national capacity and view external actors as more threatening and competitive compared to leaders who combine trust with low in-group bias. Leaders with high in-group bias and low trust thus believe that their country ought to confront evil adversaries (Hermann 2005) — consistent with psychological research connecting beliefs about the group’s moral superiority to outgroup animosity. Shannon and Keller (2007) examine officials from the George W. Bush administration. They link this trait combination to the administration’s decision to buck international norms and invade Iraq. Related, Hymans (2006) argues that oppositional nationalists, those leaders who contrast themselves with a threatening adversary, have a stronger desire for nuclear weapons compared to other leaders.
However, a broader look at the field suggests that readers take pause before concluding that nationalism necessarily prompts individual belligerence (Lind & Ueki 2021). Some evidence casts doubt on key mechanisms, like threat inflation and low trust: Jones (2014) shows that U.S. study abroad students see their host country as less threatening when they return. Diminished nationalism from their experience does not explain these reduced threat perceptions. Instead, study abroad inflates respondents’ sense of national superiority, decoupling nationalism from this important perceptual outcome. Chung’s (2023) experiments in South Korea and Japan imply a similar conclusion about nationalism and trust, as affirming national identity raises international trust rather than lowering it (see also Chung 2015). Affirmed respondents also endorse cooperating with other countries at higher rates.
Other research identifies factors that weaken the connection between nationalism and support for conflict. Ko (2023) cautions that nationalists demand both hawkishness and complete victory. Elites therefore dampen their calls for war and demonstrate restraint when they believe that fighting risks defeat. Others argue that the connection between nationalism and conflict support depends on the specific manifestation of nationalist meaning and norms. Bonikowski and DiMaggio (2016 963) conclude that U.S. “creedal” nationalists believe in national superiority and value “liberal principles.” Their support for war falls in the middle when compared to other types of nationalists in the authors’ 4-part typology, suggesting that some nationalists hold more hawkish views than others. Powers (2022) in turn argues that nationalist hawkishness is a contingent outcome: Nationalists adhere to their group’s dominant norms and values. These norms sometimes favor conflict, but other times do not. Similarly, Ko’s (2022) experiment shows that reminding Chinese respondents about their national achievements stimulates nationalism without increasing militarism. Collectively, these studies raise important questions about when and why nationalism’s microfoundations favor international conflict.
Nationalism as a cause of international conflict
A parallel research program examines whether nationalism breeds or spreads militarized international conflict. The state of this research echoes its microfoundational counterpart: Many studies present evidence showing that nationalism causes war. Others add important qualifications to these conventional expectations. This section reviews evidence linking nationalism to conflict via nation-building, territory, domestic political incentives, and country-wide nationalist surges before discussing recent research on nationalism’s potential to foster non-conflict outcomes.
Some scholars treat nationalism and war as intertwined via nation-building. Several studies claim that the number of international wars and the way actors fight wars changed as nation-states emerged and spread through the system (Cederman, Warren & Sornette 2011; Wimmer 2013). Indeed, scholars attribute at least three types of interstate conflicts to nationalism and nation-building. First, nationalism propels wars when stateless nationalities seek sovereignty, in line with principles of self-determination (Van Evera 1994; Woodwell 2007; Mearsheimer 2011). Such conflicts arise from an imbalance between states and nations and often lead to regional wars (Miller 2007). Second, nationalism prompts conflict when actors use military intervention to recover national diaspora communities. States can launch military interventions to reunite lost kin (Mylonas 2013). However, the likelihood that a state pursues such violent irredentism depends on several factors including shared boundaries, international pressures, domestic politics, and the content of nationalism (Saideman & Ayres 2008). Third, leaders may provoke international conflict to consolidate national unity against a foreign adversary — a dynamic that explains Bismarck’s motivations in the Franco-Prussian war, for example (Sambanis, Skaperdas & Wohlforth 2015).
Nationalism also contributes to explaining why territorial disputes so often escalate to war. Territorial conflict is more likely when the disputed territory holds intangible value (Hensel & Mitchell 2005). Nationalism constitutes one key component of intangible value. For example, domestic political dynamics create territorial “homelands” that bind nationalism to physical land, rendering some tracts more nationally significant than others (Shelef 2020). States engage in conflict at greater rates after they lose homeland territory compared to non-homeland territory (Shelef 2016). Nationalism also contributes to territorial indivisibility, though Goddard (2010) notes that nationalism alone cannot account for this phenomenon. Goddard explains that Jerusalem is “indivisible” because Israeli and Palestinian elites used religious and nationalist rhetoric to legitimate their claims to the city. These legitimation strategies foreclosed compromise and make Jerusalem a flash point for conflict.
Another strand of research examines how domestic political dynamics foster nationalist conflict. Some institutional or domestic factors create incentives for leaders to promote nationalism in their population, catalyzing international conflict. Mansfield and Snyder (2004) and Snyder (2000) argue that leaders in democratizing countries may stoke nationalism to build popular support without bearing the full costs of democratic accountability. This nationalist myth-making leads to military conflict through unchecked logrolling among nationalist elites or by locking leaders into the nationalist tactics they used to secure mass support. Ciorciari and Weiss (2016) build on this insight, proposing that weakly institutionalized democracies are more likely to allow nationalist protests and adopt aggressive foreign policies in response to such protests compared to other regime types, including electoral autocracies and established democracies. Nationalist protests carry high risks to regime stability and are relatively costly to repress for weakly institutionalized democracies. Finally, leaders in ethnically diverse societies may use nationalism to fend off domestic challenges, exploiting nationalist myth-making opportunities to promote a narrative that the nation excludes some ethnic groups (Gagnon 1994). This approach increases the likelihood that a state engages in violent conflict with neighboring countries along the lines of the ethnic cleavages promoted in the nationalist myth.
Quantitative studies evaluate whether aggregate trends support the claim that nationalism catalyzes military aggression, complementing the extensive body of qualitative nationalism scholarship. Schrock-Jacobson (2012) provides the first large-N evidence testing nationalism’s effect on interstate war onset from 1816 to 1996. Schrock-Jacobson (2012) creates an original nationalism index for each country-year in the data. The index summarizes several proxies for nationalism, such as whether the state contains a politically salient nationalist party or attempts to limit rights for domestic groups not considered as part of the nation. The results show that high nationalism scores in one year predict a higher probability that a state will go to war in the following years, though the strength of this relationship depends on the type of nationalism. Of course, a confounding variable could explain both the rise in nationalism and conflict in any observational study.
Later work uses research designs that establish a causal relationship between nationalism and war. Gruffydd-Jones (2017) exploits the exogenous timing of annual national holidays. He finds that international conflict increases in the two months following national days, and attributes this pattern to the presumed nationalist surge that accompanies such events. Additionally, Bertoli (2017) used a regression discontinuity design to establish a causal relationship between a country’s participation in the men’s football World Cup and war. The analysis assumes that international sports competition raises nationalism in participating countries. It shows that barely qualifying countries engage in more subsequent militarized interstate disputes compared to those countries that just missed the qualification standards.
This research program also contains nuance about the extent that nationalism leads to international conflict. Both Snyder (2000) and Schrock-Jacobson (2012) conclude that civic nationalisms generate less conflict than their ethnic or counterrevolutionary counterparts, for example. Hutchinson (2017) emphasizes the complexity of the relationship between nationalism and conflict by noting that strong nationalism sometimes contributes to resolving disorders. Mearsheimer (2011) suggests that nationalism may decrease the probability of war by making it a costly and protracted endeavor. Nationalism imbues war with heightened symbolic value. It therefore increases resistance and the costs associated with territorial occupation by foreign powers. Similarly, Ko (2023) claims that under some conditions, popular nationalism has a restraining effect that suppresses the likelihood of conflict and helps maintain the status quo. When leaders are politically vulnerable and anticipate that they are unlikely to bring home a shining victory, they are less likely to channel nationalism into conflict. These studies challenge the prevailing assumptions behind the conventional wisdom that nationalism spreads conflict, highlighting the need to reevaluate our understanding of this complex relationship.
Whose nationalism matters and how?
At the actor level, several potential routes connect nationalism to conflict initiation. A leader might choose to use force because they harbor nationalist beliefs, for example. Or hawkish leaders could instigate mass public nationalism to gain domestic backing for their military adventures. Conversely, the nationalistic public could pressure leaders to initiate unwanted conflict. Elite and mass nationalism have distinct and interactive implications for conflict, yet much macro-level research either centers political elites (Gagnon 1994; Snyder 2000; Mansfield & Snyder 2004) or remains ambiguous regarding whose nationalism drives outcomes (Schrock-Jacobson 2012; Bertoli 2017). Research on microfoundations favors attitudinal outcomes, such that few studies directly examine how public nationalism influences the likelihood of conflict (Ciorciari & Weiss 2016; Gruffydd-Jones 2017; Ko 2023). Bridging existing gaps in theories that link nationalism to war thus requires research that unpacks the dynamic relationships between elites, citizens, and conflict.
Elite and popular nationalism take different forms. Elite nationalism manifests variously as a personality trait (Hermann 1980), leaders’ nationalist policy agendas, or leaders exploiting nationalism to legitimize their rule (Gagnon 1994; Mansfield & Snyder 2004). Rising nationalist political parties also capture elite nationalism in the political process (Schrock-Jacobson 2012). By contrast, popular nationalism is a widespread social phenomenon characterized by the presence of nationalistic sentiments among the general public (Ko 2023). Elite manipulation can prompt public nationalism. But grassroots movements or significant events — like national holidays or international sports competitions (Gruffydd-Jones 2017; Bertoli 2017) — also stoke public nationalism from the bottom-up.
These distinctions between elite and public nationalism imply different conflict-generating processes. Snyder (2000), for instance, identified several pathways from elite nationalism to militarized conflict. These include logrolling among nationalist veto groups and a competitive dynamic among elites that leads to increasingly extreme and assertive nationalist claims, for example. Each pathway culminates in nationalist bidding wars. Popular nationalism could spark direct aggression between competing states’ citizens that draws their states into militarized conflict. This route describes the 1969 football war between Honduras and El Salvador (Bertoli 2017), but remains rare. Ciorciari and Weiss (2016) and Ko (2023) instead show that popular nationalism primarily produces military aggression through public pressure on leaders (see also Zhao 2013). Leaders’ domestic political calculations and institutions shape how they respond to nationalist pressure from below.
Several important questions remain unresolved about these processes that connect nationalism to international conflict. First, how do leaders’ own nationalistic beliefs shape their responses to popular nationalism? Existing research typically omits the public from the equation when establishing that leaders’ nationalism influences their foreign and security policy. Many models assume that leaders are rational actors who weigh the costs and benefits of conflict initiation even when confronting popular nationalism, but a leader’s own nationalistic beliefs may bias their judgments. Gruffydd-Jones’s (2017) study implies that nationalistic leaders will more readily exploit public nationalism to suit their aims. This proposition hints that public and elite nationalism have mutually reinforcing effects on conflict initiation. These interactions suggest that understanding the trajectory from nationalism to conflict requires systematic research on whether and when public and leader-level nationalism reinforce or counteract each other to shape a leader’s decision-making process. Such nuanced investigations will significantly improve our understanding of the intricate interplay between elite and public nationalism in conflict initiation.
Second, how does the public respond to elite nationalism? Existing research often assumes that a homogeneous public will align with elite nationalism as it escalates towards war. But elite attempts to foment public nationalism often fail (Whitmeyer 2002). Elites may only captivate the most nationalistic subset of their target audience, or the smaller subset of citizens who share their views about what nationalism means. These considerations raise questions about political persuasion and selling nationalism to a diverse public (Snyder 2000). For example, what elite-led tactics or messages strengthen nationalist beliefs among key constituencies? Which persuade the public to support military ventures? Are there specific domestic circumstances, such as economic hardships or increasing immigration, that render the public more susceptible or receptive to endorsing elite nationalism and calling for war? When are elite attempts most likely to fail? Exploring these questions will allow scholars to more fully grasp how the two agents of nationalism interact in sparking international conflict.
Content
Some nationalisms prompt support for conflict, whereas others do not. Reviewing both the micro- and macrolevel evidence hints that beliefs about a nation’s superiority do not automatically inflate threats nor cause war. Actors experiencing similarly intense feelings about their country may adopt distinct foreign policy stances. And nationalism scholars have long separated nationalisms into different types, distinguishing war-prone ethnic, exclusive, or malignant nationalisms from their benign civic, inclusive, or enlightened counterparts (Kohn 1944; Snyder 2000; Schrock-Jacobson 2012; Tudor & Slater 2021; Jones 2014; Brown 2000; Aridici 2019). Research on content — “the meaning of a collective identity” (Abdelal et al. 2006, 696) — attempts to explain the fluctuating relationship between nationalism and conflict.
The inconsistent link between nationalist content and individual foreign policy preferences has psychological foundations. Powers (2022) argues that strong group memberships encourage conformity to the group’s norms (see also Terry & Hogg 1996; Theiss-Morse 2009). If those norms require that members protect their united group from outsiders, hawkishness should prevail among nationalists. But some dominant norms suppress militarism, like commitment to the liberal American Creed (Bonikowski 2016) or reciprocity norms (Powers 2022). Content differences link nationalist beliefs to both hawkish and dovish policy preferences.
Macro-level work divides states according to their dominant nationalism and, like the micro-level work, argues that some nationalisms are more war-prone than others. This research program has long approached varieties of nationalism using the dichotomous civic/ethnic framework (Kohn 1944). Ethnic nationalisms broadly imply a kinship among co-nationals. Researchers typically connect ethnic nationalism to conflict, arguing that ethnic nationalists endorse wars to preserve their national character or unite co-ethnics in one territory (Snyder 2000; Schrock-Jacobson, 2012). By contrast, standard accounts characterize civic nationalism as inclusive, a nationalism that accommodates all citizens via democratic institutions. Civic nationalism predicts prudence under threat (Schrock-Jacobson 2012). Yet scholars have long criticized this dichotomy on normative, conceptual, and measurement grounds (Nieguth 1999; Kuzio 2002; Brubaker 2004). Some in turn reject the framework and create complementary schemes (Saideman & Ayres 2008). Moreover, research about civic/ethnic nationalism and war must address two outstanding challenges. At the micro-level, central causal claims about the mechanisms that link civic and ethnic nationalisms to distinct foreign policy attitudes remain untested. At the macro-level, typical state-level classifications mask important within-country variation over how citizens define their country’s nationalism (see Bonikowski 2016 for a similar critique). Different citizens or leaders adopt distinct nationalist commitments, further suggesting limits on our capacity to draw firm conclusions about whether and when a state’s ethnic or civic nationalist character prompts versus suppresses conflict.
Research on varieties of nationalism casts new light on core assumptions about nationalism’s conflict-prone character while raising important questions for future work. First, which nationalisms cause militarism? Research has produced a cornucopia of concepts to replace the civic/ethnic dichotomy, creating new insights about nationalism and conflict. But these siloed programs impede synthesis. Scholars studying nationalism and conflict could fruitfully work toward common conceptual frameworks that combine inductive (Bonikowski & DiMaggio 2016) and deductive insights (Tudor & Slater 2021) about content and move beyond the civic-ethnic framework. Furthering cross-subfield and cross-disciplinary dialogues will aid this effort. Second, which nationalist norms promote support for cooperation or aid? Nationalism scholars should investigate whether and when nationalism promotes non-conflictual foreign policies. Research on status motivations could prove generative. Some states seek to enhance their status by demonstrating moral superiority, for example (Wohlforth et al. 2018). Insofar as status concerns and nationalism share common foundations, some nationalists should favor foreign aid over conflict.
Conclusion
The belief that nationalism is a primary cause of militarized conflict long went unchallenged in international relations (Van Evera 1994). The past few decades have featured significant progress in providing evidence for claims about nationalism’s aggressive nature. However, it is premature to conclude that nationalism universally drives international conflict. Our review suggests that additional progress requires asking under what conditions nationalism leads to conflict and how nationalism contributes to the causal processes that produce war.
Our review identifies two possible conditions under which nationalism causes conflict. Each merits deeper investigation. First, nationalism appears to amplify the odds of conflict when tied to an explicit political goal. Scholars observe conflict when nationalist appeals concern sovereignty (Miller 2007), the return of homeland territory (Shelef 2016), uniting ethnic kin (Saideman & Ayres 2008; Mylonas 2013), or confronting a rival (Gruffydd-Jones 2017). Research comparing undirected nationalism to nationalism attached to unfulfilled aims would inform this speculative pattern. Second, the connection between nationalism and conflict appears strongest when nationalism implies out-group distrust or animosity. Outgroup animosity is not inherent in nationalism (Powers 2022). Yet once it has been established and activated, increasing an out-group’s salience creates an aggressive nationalism (Ko 2022). When nationalism implicates a sharp distinction between insiders and outsiders, both micro- and macro-level studies find that it correlates with conflict at higher rates. This category includes the distrusting and oppositional worldviews that characterize aggressive citizens and leaders (Hermann 1980; Hymans 2006; Federico, Golec & Dial 2005) alongside the ethnic and counter-revolutionary nationalisms that center internal and external “others” in nationalist rhetoric (Schrock-Jacobson 2012; Snyder 2000).
Research should also place equal weight on identifying when nationalism does not produce conflict or aggression. As our review shows, concluding that nationalism universally sparks international conflicts is not warranted. Promising possible conditions include when nationalism is directed at internal qualities, such as affirming national identity or celebrating national achievements (Chung 2015; Ko 2023), when it is built on broadly liberal principles, such as equality, diversity, and tolerance (Bonikowski & DiMaggio 2016; Schrock-Jacobson 2012; Snyder 2000; Powers 2022), or when nationalism is paired with circumstances that enhance out-group trust (Jones 2014). Overall, these possibilities suggest that research on nationalism and conflict should attend to the diverse repertoire of nationalism and the situational contexts within which nationalism manifests. Finally, analyzing the relationship between nationalism and conflict requires that scholars identify the agents who experience, promote, or define nationalism. Nationalism has been implicated in several parts of the conflict process, including as a cause, effect, or mechanism for leaders to gain domestic support. Knowing who promotes which forms of nationalism — and when — will enhance conceptual clarity and advance a holistic understanding of nationalism and international conflict.
- 1Of course, rally effects and related phenomena suggest that nationalism is partly endogenous to war (Mueller 1973).
- 2See e.g., Druckman (1994), Huddy and Khatib (2007) Gries et al. (2011), and Herrmann, Isernia, and Segatti (2009) for arguments distinguishing nationalism from related attitudes about the nation (cf. Bonikowski 2016).
