The Extremist's Advantage in Civil Wars

One of the puzzles of the current wave of civil wars is that rebel groups espousing extremist ideologies—especially Salafi jihadism—have thrived in ways that moderate rebels have not.¹ Groups such as Jabhat al-Nusra and the Islamic State (also known by the acronym ISIS) have attracted more recruits, foreign soldiers, and financing than corresponding moderate groups such as the Free Syrian Army, Ahlu Sunna Waljamaa, or Jaysh Rijaal al-Tariqa al-Naqshbandia (JRTN).² The proliferation and success of extremist groups is particularly surprising given that their goals are far more radical than those of the populations they seek to represent.³ Salafi jihadists aim to establish a transnational caliphate using military force, an objective the vast majority of Muslims do not support.⁴ Why have so many extremist groups emerged in countries experiencing civil wars since 2003, and why have they thrived in ways that moderate groups have not?

This article has two goals. The first is to provide a theoretical framework for understanding the role of ideology, especially an extreme ideology, in civil wars. It argues that an extreme ideology can offer rebel entrepreneurs significant organizational advantages over more moderate groups, especially in environments with multiple competing rebel groups, weak rule of law, and bad governance. The second goal is to apply this theory to current civil wars in Muslim countries in order to explain the rise of radical Islamist groups since 2003.

The article argues that under certain conditions, rebel leaders (such as Abu Bakr al-Baghdadi of the Islamic State) have strong incentives to embrace an extreme ideology even if they do not believe the ideas that underlie it.⁵ The same is true of more moderate citizens who choose to support or associate with these groups.⁶ Average citizens may have incentives to join or collaborate with an extreme rebel group if they feel that such a group is more likely to win a war and resist corrupting influences once in power. The initial leaders of ISIS, for example, were a mix of religious zealots (Abu Ayyub al-Masri and Abu Bakr al-Baghdadi), disgruntled tribesmen, and members of Saddam Hussein's secular Baathist regime.⁷ These individuals then built their organization by recruiting foot soldiers largely ignorant of Salafi tenets and practices.⁸ The recent rise of radical Islamist groups, therefore, does not necessarily indicate an increase in support for radical ideas in Muslim countries experiencing civil war as much as it may reveal average Sunnis behaving strategically during uncertain and difficult times.

The core of the argument is that an extreme ideology can help rebel elites overcome three organizational challenges that may arise as they seek to build movements in highly competitive, low-information environments.⁹ The first is a potentially debilitating collective-action problem.¹⁰ To mobilize and maintain an army, rebel leaders must convince at least some individuals to pay the high costs of fighting, a requirement that most people would prefer to avoid. Normally, rebel groups attempt to overcome collective-action problems by offering recruits private rewards in the form of money, security, or access to plunder. Extremist groups, especially faith-based groups, have a particular advantage in the provision of private goods, because they can offer cheap, deferred compensation in the form of an “eternal afterlife” or “rewards in paradise,” which nonreligious ideologies cannot do.¹¹ They can also promise a potentially devastating type of personal punishment (eternal damnation in the case of Christianity and excommunication in the case of Islam) that is both costless to enforce and impossible for targets to escape.

The second organizational challenge comprises two potentially harmful principal-agent problems.¹² To evade capture and avoid defeat, rebel leaders must recruit soldiers who will remain committed and loyal to the organization even after they are deployed to the field. An extreme ideology can help overcome this agency problem by screening out less committed soldiers, which then reduces the problem of poor performance, side-switching, and betrayal. Rebel leaders can also use an extreme ideology to signal their own dedication to a cause, allowing them to attract more devoted and hard-fighting soldiers to their ranks.

The third organizational challenge is a potentially destabilizing commitment problem. To successfully compete against other factions fighting a war, rebel leaders must reassure their soldiers and supporters that they will resist corruption once in power. This is especially important in countries with few institutional constraints on government elites and a history of exploitation. An extreme ideology, especially one that demands personal sacrifices from its leaders, could serve as a way for rebel elites to credibly commit to more principled behavior once in office in a way that competing groups cannot. Taken together, these three challenges could help explain why ideologically extreme rebel groups might outperform moderate groups even in environments where the preferences of most citizens are not extreme.

This argument represents a significant departure from the conventional literature on civil wars in three important ways. First, it starts from the assumption that adopting a specific ideology is a strategic decision made by rebel leaders and not simply an extension of the underlying beliefs or grievances in a society. Until now, most studies of civil war have treated the choice of ideology as exogenous to the war; the goals and beliefs of rebel groups were assumed to reflect preexisting societal cleavages and the political disagreements that emerged from them.¹³ In contrast, this article argues that rebel leaders choose an ideology based in part on the cleavage structure of society but also on a real desire to outmaneuver and outcompete other factions fighting a war.¹⁴ The choice of ideology, therefore, is likely to be at least partly influenced by the endogenous dynamics of the war itself: the number of rebel groups vying for power, the quality of local information networks, and the strength of institutional checks on government behavior.¹⁵

Second, this article views the stated ideology of a rebel group as a form of cheap talk. Until now, most studies of civil war have assumed that the goals and ideas endorsed by warring factions were genuine. This article argues instead that rebel elites, their soldiers, and rank-and-file sympathizers likely understand that public declarations about ideology are potentially empty words that may or may not be backed by real action. The leaders of the Kurdish-Iraqi group Ansar al-Islam, for example, had invested for years in public propaganda designed to distinguish their group from the Islamic State, only to merge with the group in 2014.¹⁶ The public's understandable skepticism about elite motives may create an opening for political entrepreneurs to adopt an extreme ideological position as a way to signal their true dedication to a cause. Salafi jihadists may be perceived as more committed to real reform than more moderate groups, because adhering to a set of extreme principles inflicts at least some costs on leaders.¹⁷ As I argue below, it is the cheap-talk nature of most ideological platforms that makes an extreme ideology, with its excessive dictates and demands, potentially informative.

Third, this article treats rank-and-file supporters of extremist groups as strategic actors in their own right and not simply blind followers to a cause. Until now, most people have viewed the supporters of extremist movements as true believers, ignoring the motivational processes of these individuals. Even if rebel elites were deemed to be strategic or self-interested in their choice of ideology, the “masses” were assumed to be more ideologically driven. This article argues, however, that not all participants in these movements need to be truly committed to an ideology to be willing to support a particular group. They need only believe that an extreme group is better positioned to deliver an outcome closer to their desired preferences than other groups competing for their support.

Still, this does not mean that all rebel leaders use ideology instrumentally or that true believers do not exist. In fact, rebel entrepreneurs require at least some true believers for an extreme ideology to be an effective strategy in war. To be successful, elites require passionate devotees to a cause who are willing to join a movement in its infancy and fight especially hard. These ideologues allow the group to outcompete rival organizations, winning early battles and making the group potentially more attractive to moderate individuals seeking to assess whom to support. An extreme ideology, therefore, can make a group attractive to both ideological and non-ideological individuals. True believers join because they are genuinely committed to the goals and principles of a movement. More practical individuals join because they believe the group is better organized, more likely to win, and less corruptible than rival groups.

Note that the theory does not claim that ideas do not matter. Even the most strategic rebel entrepreneur understands the benefit of choosing a set of ideas that already resonates with local citizens.¹⁸ It would make no sense to embrace an Islamist ideology in a majority-Christian country or white nationalism in the Democratic Republic of Congo. To have any chance of success, rebel entrepreneurs must choose a set of ideas that coincides with the interests of at least a subset of society. It is no surprise, for example, that most rebel groups in Iraq, Libya, Syria, and Yemen have embraced political Islam as their base ideology, given that it is favored by large majorities of Muslim citizens in those countries. Instead, this article argues that rebel entrepreneurs will strategically emphasize those elements of an ideology that provide them the greatest competitive advantage given the strategic conditions on the ground.

The finding that an extreme ideology can be an effective tool of war under certain conditions could have potentially far-reaching implications for policymakers struggling with the rise of violent extremist groups around the world. Since the terrorist attacks of September 11, 2001, the United States has been grappling with how to reduce the growth and influence of Salafi jihadist groups whose goals directly threaten U.S. interests. If such groups are growing in number because Muslim citizens are becoming more radical in their beliefs, then successful counterstrategies must attempt to change these beliefs—a monumental task. If, however, citizens choose to support these groups for more practical reasons—because Salafi jihadist groups are better able to build an effective fighting force or offer greater reassurance against corruption—then effective counterstrategies need only address the conditions that make support for these groups advantageous. Eliminate the underlying conditions that make an extreme ideology expedient to embrace, and you eliminate the incentives elites and moderates have to back it.

What follows is divided into five sections. In the first section, I explain what this article does and does not do. In the second, I consider the existing literature on the role of ideology in civil war and define the concepts of “ideology” and “extremism.” In the third section, I lay out a theory of the strategic use of extreme ideology in civil war. This includes the three strategic problems that elites face when attempting to build a rebel organization, the conditions under which these problems are likely to be especially severe, and the ways in which an extreme ideology may help to reduce or eliminate them. In the fourth section, I use this theoretical framework to explain the rise of radical Islamist groups in civil wars since 2003, especially Salafi jihadist groups. In the final section, I outline the implications that this research could have both for scholars studying civil war and for policymakers struggling to address the rise of al-Qaida, ISIS, and other Salafi jihadist groups around the world.

This is an article about the potential benefits that rebel elites may gain by adopting an extreme ideology, especially a religious ideology, and the practical benefits moderate citizens may gain for backing these elites. The theory, therefore, applies to extremism that emerges in the context of a civil war, by a group pursuing violence, and that is religiously rather than nonreligiously based. The article does not directly address extremist ideology outside the civil war context, such as the use of extremism in the give-and-take of conventional politics. It also does not consider nonviolent extremism practiced by groups such as the Amish or nonreligious extremism such as Adolf Hitler's use of Nazism in the 1930s and 1940s. Still, I suspect that the theory is likely to apply to situations with similar characteristics to civil wars: circumstances where groups are competing for power under conditions of rapid political change and weak enforcement mechanisms.¹⁹ These are the environments in which collective-action problems, principal-agent problems, and commitment problems are likely to be particularly severe and where advantages are likely to accrue to organizations that best solve these problems. The degree to which the theory generalizes beyond religious extremist groups in internal conflicts, though extremely important, is left to future research.

This is also not an article about the origins of ideology in a given society. It does not address where ideas come from, why they resonate with certain populations but not others, or how they change over time.²⁰ Moreover, it is not an article about the means by which citizens may be indoctrinated with one set of ideas over another; that is a topic best left to experts in psychology or education. All of these topics are worthy of serious study but are beyond the scope of this article.

An extensive review of the literature on civil wars finds no book and only three articles on the role of ideology in civil war.²¹ One of the articles uses quantitative analysis to examine whether ideology influenced different players in Colombia's civil war.²² The authors found that it did: ideology allowed paramilitaries and guerrillas to distinguish themselves from each other, and it influenced the beliefs of soldiers over time. The second article summarizes the ways in which ideology could affect the behavior of rebel groups in civil war, including how it might influence their organization, activities, and mobilization.²³ A third article argues that ideology, especially radical ideologies, is necessary to mobilize individuals.²⁴ A number of other articles mention ideology, but in ways not central to their main arguments.²⁵ This article offers a theoretical framework for the role of ideology in civil war that serves as a blueprint for a more ambitious research program on the subject.

The article defines ideology, in its simplest form, as a set of beliefs about the proper order of society and how it can be achieved.²⁶ It is, according to Anthony Downs, “a verbal image of the good society and of the chief means of constructing such a society.”²⁷ All rebel groups pursuing political violence embrace some form of ideology, whether implicit or explicit; political contestation at its heart is the fight over how a country should be governed. The core ideology of communism, for example, is economic equality through the elimination of private property. The core ideology of Salafi jihadism is a return to a “pure” state of Islam via the institutionalization of the caliphate.²⁸

Extremism is trickier to define.²⁹ If one defines a group as “extremist” based on whether it uses violence to achieve its goals, as many people do,³⁰ then this definition encompasses every rebel group in every civil war that has ever been fought. Such a definition is unhelpful in explaining variation in the level of extremism across groups fighting the same civil war. Both ISIS and the Free Syrian Army, for example, are rebel groups involved in the Syrian civil war, yet they are not comparable in their level of ideological extremism. The challenge for scholars is to formulate a measure of “extremism” that does not rely on specific modes of conduct or on value judgments made by the researcher about the radical nature of a group's goals and ideas.

This article defines ideological extremism in relation to the majority opinion of the affected population on a key ideological dimension.³¹ An important dimension in the Muslim world is the proper interpretation of the role of Islam in society, with the policy space ranging from more conservative and strict to more liberal and tolerant. The majority position on the role of Islam in Muslim society is consistent around the world. According to a survey of 38,000 Muslims in thirty-nine countries by the Pew Research Center, most Muslims (including those in the Middle East and North Africa) favor both democracy and a prominent role for Islam in the political life of their country.³² Clear majorities of Muslims around the world also strongly reject violence in the name of Islam.³³ This finding extends even to Iraq, where 91 percent of Muslims in 2013 said that suicide bombing was not justified, even during war.³⁴ These majority opinions offer a baseline for what “moderate” and “extreme” mean in the Muslim world. Groups such as the Muslim Brotherhood that believe that modern democratic institutions are compatible with Islam and support democratic processes, therefore, would be classified as “moderate Islamists.”³⁵ Groups such as the Salafists, which reject democracy and adhere to a very narrow and conservative version of Islamic law, would be classified as “extreme Islamists.”

In a competitive environment, where groups are fighting over the definition of an ideal government, choosing an ideology on the extreme end of societal preferences seems destined to fail. By definition, the number of citizens holding these extreme views is likely insufficient to ensure that these movements prevail over more moderate ones. The rise of Salafi jihadists defies this logic. Groups such as ISIS, Jabhat Fateh al-Sham, al-Qaida, al-Shabaab, and Boko Haram have all succeeded in outcompeting other groups to conquer and control territory, an achievement that requires at least the implicit support of the local population. It is the extreme nature of their beliefs relative to the majority opinion that makes the growth and survival of these groups so perplexing.

This article offers a theory for the rise of violent extremist groups that reveals the conditions under which individuals will have strategic incentives to behave as if they believe in an extreme ideology even if they do not. Assume that there are three main types of actors in a civil war: political entrepreneurs who are fighting to gain political power, moderate citizens who must determine which of the competing political elites to support, and ideologues who are devoted to a particular cause.³⁶ The goal of political entrepreneurs is to win the war and gain power. The goal of moderate citizens (beyond basic survival) is to align with those political elites most likely to win the war and institute policies most closely associated with their own political preferences. The goal of ideologues is to establish their perfect vision of society. To win the war, political entrepreneurs must gain the support of at least some of the moderate citizens who represent the majority of the population; the more soldiers and sympathizers a group is able to attract, the more likely it is to win the war.

Political entrepreneurs who seek to build and sustain a rebel organization confront three organizational challenges that, under certain conditions, may create strong incentives for them to embrace an extreme ideology. First, rebel entrepreneurs often face a substantial collective-action problem—what Mark Lichbach called the “rebel's dilemma.”³⁷ To be successful, rebel entrepreneurs must find a way to recruit individuals willing to fight and die for a cause even when the benefits of victory will be shared with those who do neither. Second, rebel entrepreneurs face a classic principal-agent problem. To be successful, rebel elites must be able to recognize and attract soldiers who will remain trustworthy and loyal once deployed to the field.³⁸ Third, rebel entrepreneurs face a commitment problem that creates incentives for soldiers, donors, and rank-and-file sympathizers to defect from the organization unless leaders can reassure them that future spoils will be shared.

Moderate citizens also face at least two challenges when seeking to determine which party to support in the midst of war. These challenges could create incentives for them to embrace a more extreme group even if their preferences are more moderate. The first is related to the outcome of war. All else equal, citizens would prefer to support the group that is most likely to win the war, because doing so would shield them from punishment related to backing the opposition. The second is related to the quality of governance. Citizens would also prefer to back the rebel group that is most likely to institute reforms, even if its ideology is not exactly aligned with theirs. In weakly institutionalized settings, citizens understand that rebel leaders have incentives to abandon costly political reforms once they are safely in power. The challenge is to determine as early as possible which political elites are more likely to resist corruption once in office.

These two challenges encourage moderate citizens to try to ascertain which of the competing rebel groups could potentially win the war and which is more likely to be trustworthy over time. Information about the relative strength of a group is fairly easy to gather; citizens can observe how groups perform on the battlefield. The more battles a group wins, the more attractive it becomes. Information about the trustworthiness of elites is more difficult to obtain; all rebel elites have an incentive to claim that they will institute reforms once in power, even if they know they will not. The desire to back the winning faction and the one least likely to sell out once in power could lead moderate citizens to shift their support in favor of more extreme groups. An extremist group that institutes at least some reforms is preferred to a moderate group that institutes none.

In what follows, I explore three organizational hurdles that elites face in the context of civil war, explain how an extreme ideology could be an effective tool for solving them, and reveal why moderates might gravitate toward these groups even if their policy preferences are less radical.

One of the first organizational hurdles that rebel entrepreneurs face when attempting to build a fighting force has to do with collective-action problems. Most citizens would prefer to reap the rewards of living under their preferred political system without having to pay the costs of fighting to install it. To be successful, however, rebel elites must convince some individuals to fight for them, a task that is especially hard in the nascent phase of a movement.³⁹

Theoretically, rebel elites can reduce collective-action problems by pursuing two possible strategies. First, they can change the payoffs that recruits receive for volunteering for battle, offering them inducements to join.⁴⁰ Soldiers can be paid a high salary or provided education and health care benefits. They can be granted permission to supplement their salaries through looting, taxing, or exploiting conquered territories.⁴¹ Soldiers can also be given things as simple as food, housing, or security. One of the attractions of the Taliban in Afghanistan, for example, was that it offered citizens protection from the arbitrary violence of warlords.⁴² Each of these inducements serves to increase the private benefits that a person enjoys by supporting an organization, enhancing incentives to fight and reducing incentives to free-ride.

A second strategy that elites could pursue is one that would impose punishments for nonparticipation in a movement.⁴³ Rebel leaders can inflict heavy costs on individuals who choose to support a competitor or remain uninvolved in a war.⁴⁴ Such action could include the forced expropriation of an individual's property or the destruction of a family's home. It could also include the targeted assassination of individuals who join the enemy or refuse to fight against it. According to one member of Boko Haram, “I officially joined them when they started killing indiscriminately. I needed protection and immunity from persecution by them so I could continue with my business.”⁴⁵ Collective-action problems disappear when the costs of nonparticipation are high.⁴⁶

Both moderate and extreme rebel groups have the ability to offer inducements and inflict punishments to solve the collective-action problem associated with recruitment. An advantage, however, will accrue to groups able to craft rewards and punishments that do not require a significant outlay of resources. The lower the economic and material costs of attracting a steady stream of recruits, the more resources that can be devoted to the war effort, and the more battlefield success a group is likely to have.

An extreme ideology based on religion is uniquely positioned to compete in this regard in at least four ways. First, religious organizations have the ability to offer costless deferred compensation in the form of promises of rewards in the afterlife. Second, many religions already include dictates that rebel leaders can use to enforce behavior in ways that benefit the organization. Salafi jihadists, for example, have invoked Islam's principle of takfir as license to kill dissenters and defectors of their movement.⁴⁷ In this way, religion could make it easier for a rebel group to engage in coercion in order to attract recruits. Third, religious leaders are often viewed as having greater moral authority and legitimacy than ordinary citizens, making it easier for them to dispense punishments without incurring civilian backlash.⁴⁸ The ruling royal family of Saudi Arabia aligned with Wahhabism for exactly this reason; the alliance gave the monarchy the status of spiritual and political heads of the land, gaining the deference of Saudi citizens. Fourth, religious organizations have the unique ability to inflict a potentially devastating type of personal punishment: eternal damnation in the case of Christianity and excommunication in the case of Islam. Not only is this punishment costless to enforce, but it is also impossible for targets to escape, as punishment follows an individual even if he or she chooses to switch sides or defect from the battlefield. Religion, thus, could create the opportunity to offer cheap, deferred inducements and punishments, enabling rebel leaders to potentially outcompete less extreme or more secular organizations. It also allows them to enter a war late, because they can undercut competitors by producing rewards and punishments more cheaply.

An important outcome of these features is that they are likely to attract a disproportionate share of ideologues to a group, especially in the early phases of mobilization. Rebel groups with a cadre of highly committed, dogged fighters not only win battles, but gain a reputation for disciplined, high-quality fighting units. This reputation then serves to attract more moderate citizens who are drawn to the group because of its dominance on the battlefield.⁴⁹ According to William McCants, the success of ISIS convinced many former fighters of the Free Syrian Army to defect for what many soldiers felt was the better-funded and better-organized jihadist group.⁵⁰ Rebel entrepreneurs who embrace an extreme ideology, therefore, could gain an early competitive advantage over more moderate groups in recruiting the very best fighters, which then translates into an advantage in recruiting less ideologically driven soldiers over time. Abu Bakr al-Baghdadi and other ISIS leaders appeared to have understood this two-pronged effect. In an attempt to attract both zealots and moderates, ISIS implemented its dictates and punishments inconsistently. When popular support waned, the leadership often became more lenient toward the local population. According to McCants, “[B]eing so strict was good for impressing puritans, but it wasn't terribly crowd pleasing.”⁵¹

Rebel entrepreneurs also face two potential principal-agent problems that an extreme ideology could help solve. The first stems from the uncertainty rebel leaders have regarding the dedication and reliability of soldiers volunteering for service.⁵² The second stems from the uncertainty that recruits have regarding the sincerity and devotion of rebel elites.

dedication and reliability of recruits. One of the challenges that rebel entrepreneurs face is that they cannot identify ex ante which volunteers will remain loyal to the organization over time. They must accept or reject soldiers based on incomplete information on how individuals are likely to perform in the field once free of elite monitoring. This lack of information is potentially problematic because soldiers (1) do not always have the same preferences as their leaders, (2) could behave in ways that hurt the organization and its elites, and (3) are difficult to monitor once deployed.⁵³

Rebel leaders understand that not all soldiers join rebel movements for equally honorable reasons. Some join because they are truly committed to the organization and its goals; others join for more self-interested reasons such as adventure, revenge, or camaraderie.⁵⁴ To simplify, assume that two types of rebel recruits exist: those who are dedicated to the organization and those who are not. Dedicated recruits are likely to remain loyal to the organization, be reliable, and fight hard. Less dedicated recruits are more likely to perform poorly, be lazy, exhibit predatory behavior, and betray the movement and its leaders to the enemy. Potential recruits know whether they are dependable. Rebel leaders do not.

One of the keys to a successful organization is the ability of rebel leaders to distinguish between dedicated and undedicated recruits before they are incorporated into the organization where they can inflict harm. One way to do this is for rebel leaders to demand a costly signal from potential recruits.⁵⁵ Costly signals can come in many forms. Leaders can demand that potential recruits go through a rigorous training period or “boot camp.” They can require great sacrifice—for example, renouncing one's former country or making a public pledge to the opposition, which then marks them as traitors to the government. Organizations could require new recruits to commit an egregious act such as rape or a gratuitous killing.⁵⁶

Once again, an extreme ideology could help determine which volunteers are likely to be committed to the organization and which are not. The costly signals described above all require that the organization expend resources. Boot camps demand money and personnel and are an inefficient way to determine commitment because only a certain percentage of recruits are able to complete the program. Public denouncements put recruits at risk of government and community reprisals, reducing the numbers of dedicated recruits ultimately available to fight. Rape and gratuitous killing may be a costly signal of commitment, but these actions alienate the local population, making local operations and occupation more difficult.

The most advantageous signals are those in which the costs are borne entirely by recruits and not rebel leaders. An extreme ideology could be such a signal. By forcing volunteers to pay high upfront costs in the form of socially alienating, group-entrapping practices, an extremist group ensures that it has chosen individuals who are more likely to remain true over time.⁵⁷ Salafi jihadists, for example, must renounce friends and family who do not embrace Salafi jihadism. They must then follow a strict interpretation of Islamic doctrine that often levies harsh, nonnegotiable punishments for even slight indiscretions. Jabhat al-Nusra went one step further, requiring all new recruits to immediately join the front line, where they were “tested for bravery, dedication, and loyalty to the organization.”⁵⁸ Individuals who intend to shirk their duties or subvert the organization are less likely to join under these conditions.⁵⁹

In addition, an extreme ideology naturally appeals to ideologues in the population—individuals at the extreme end of the preference distribution who have more to gain by fighting.⁶⁰ Because the difference between winning and losing is larger for individuals with extreme preferences than for moderates, these individuals are willing to absorb heavier costs to attain victory.⁶¹ More committed recruits, therefore, naturally gravitate toward more extreme ideological groups, creating a helpful separating equilibrium.

Finally, Jacob Shapiro argues that religious groups may have an additional advantage screening potential recruits given their large social networks. Hamas, for example, was better able to identify, monitor, and control its members as a result of its rich array of social services than was its secular competitor, Fatah.⁶²

trustworthiness of rebel leaders. Rebel leaders, however, may also face a reverse principal-agent problem. High-quality, dependable soldiers will attempt to identify which of the competing rebel factions have equally honorable leaders. Highly dedicated soldiers understand that rebel leaders have incentives to claim they are dedicated to political change even if they are really motivated by ambition or greed. How do these citizens determine which leaders to back and which to avoid?

Dedicated and determined citizens can identify more dedicated leaders via a basic signaling game. Assume that there are two types of rebel leaders: those who believe in the goals and principles of the group and those who do not. Rebel leaders know their type; citizens do not. Elites can claim that they are devoted to a particular set of goals, but because all leaders have incentives to present themselves this way, these claims are the equivalent of cheap talk. One opposition leader in Syria, for example, bluntly admitted that many Free Syrian Army commanders lacked discipline and that the question every Syrian had for the opposition was, “Are you going to bring chaos or order?”⁶³ Determining which leaders are truly devoted to reform becomes a critical task not only for the most fervent supporters but for moderate supporters as well.

Rebel leaders who are able to devise costly signals of their dedication are likely to attract a greater number of high-quality soldiers needed to win a war. Rebel leaders have at least two ways to do this. The first is to choose a set of ideals on the extreme end of the ideological spectrum.⁶⁴ Leaders who pick an extreme ideology suggest that they are in it not just for the power or self-enrichment but because they truly care about political change. The second is to choose an ideology that demands personal sacrifice from the leaders, something that religious extremism often requires.⁶⁵ Strict guidelines on elite behavior signal to potential followers that the leaders may be equally committed to a cause. Osama bin Laden's decision to embrace Salafism imposed significant behavioral and financial constraints that allowed him to distinguish himself from many of his competitors.

Rebel leaders face one final organizational hurdle. Even if they are able to solve collective-action problems (by offering inducements or punishments to individuals to fight), and even when they are able to solve principal-agent problems (by identifying dedicated supporters and creating costly signals of their own devotion), they may still have difficulty maintaining the long-term support of citizens because of commitment problems.

Potential supporters of rebel groups know that rebel leaders, once in power, have incentives to use their office for personal enrichment even if they had no intention of doing so during the war.⁶⁶ That is because the payoffs for centralizing power and stealing from the state radically change once a group wins the war, especially in weakly institutionalized settings.⁶⁷ Rebel leaders who are best able to commit to good governance in the future, therefore, are likely to gain additional moderate support during the war.⁶⁸

Again, an extreme ideology may have three advantages here. First, groups on the ideological extreme are likely to have an easier time committing to more far-reaching reform than moderate groups. In bargaining contexts, it is often useful to be represented by an agent who is more hard-line.⁶⁹ Hard-line agents will reject deals that more moderate agents would accept, forcing an adversary to make a better offer.⁷⁰ Palestinians, for example, might prefer Hamas as a negotiating agent with Israel to Fatah, because Hamas is more likely to reject mediocre deals.⁷¹

Second, extreme ideologies frequently attempt to control all aspects of people's lives, making their behavior more predictable over time.⁷² In her analysis of totalitarian movements, for example, Hannah Arendt emphasizes the ways in which extremist groups seek to eliminate all forms of spontaneous human action and freedom, reducing the unknowns associated with future behavior.⁷³ The same concept helps violent extremist movements credibly commit to future reform.

Third, moderate citizens understand that ideologically extreme rebel groups include true believers who could punish leaders who renege on promises. The presence of ideologues within the party, therefore, helps leaders credibly commit to at least some accountability after the war has been won.

Religious extremist groups, however, may have an added advantage over secular groups in terms of committing to good behavior over time. Centralized religions often have their own infrastructure for justice. Radical Islam, for example, comes with its own jurisprudence—a system of laws interpreting nearly every facet of governance with a wide variety of interpretative forums from which to draw. The leadership of al-Qaida appeared to understand this advantage by purposively targeting “regions beset by anarchy, where local populations would welcome their ability to institute basic governance and Islamic sharia law.”⁷⁴ Religion, especially Islam, also has trustworthy third parties willing to step in to arbitrate disputes and punish leaders—imams, muftis, and ayatollahs are just some examples.⁷⁵ Their presence could play an important role in allowing Islamist rebel leaders to outcompete more moderate groups on this dimension.

The theory outlined above explains how an extreme ideology may help rebel entrepreneurs overcome the three organizational hurdles discussed above and, in the process, recruit and retain more soldiers and sympathizers. It also explains the benefits that an extreme ideology may offer to more moderate citizens if they believe it will help a group win a war and resist corruption. The theory does not, however, explain the conditions under which embracing an extreme ideology is likely to be more or less advantageous to both groups. In what follows, I argue that three conditions are likely to produce particularly severe collective-action, principal-agent, and commitment problems and that it is these conditions that favor the emergence and success of extremist groups. These conditions—periods of rapid political change, intense competition, and limited constraints on executive power—frequently occur in countries with authoritarian regimes in the throes of civil war. These conditions also exist in Muslim countries experiencing civil war today.

Elites seeking to change the political status quo cannot pick just any ideology. Those who hope to have some chance to attract recruits are limited to political ideas that resonate with some portion of the population they hope to govern.⁷⁶ Populations will have preexisting ideas about how things “ought to be” and what an “ideal” government might look like.⁷⁷ These ideas are likely to be influenced, in part, by historical lines of political contestation, which often parallel ethnic, religious, sectarian, or class divisions.⁷⁸ The choice of ideology, therefore, will depend on these preexisting lines of contestation; this is the element of ideology that is exogenous to the war itself and does not change rapidly over time.

Every ideology, however, falls along a continuum from moderate to extreme. Rebel entrepreneurs, therefore, must also choose where along this continuum to place their movement. This is where the endogenous civil war environment comes into play. Three contextual factors are likely to create incentives to move to the ideological extreme. The first involves the level of competition in a given war. Collective-action problems are likely to be particularly severe when multiple rebel groups exist, all of which seek to appeal to the same subset of the population. After Saddam Hussein was deposed in 2003, multiple insurgent forces emerged within both the Sunni and Shia populations to fight for control of Iraq. The greater the number of rebel factions seeking to represent the same population, the more intense the collective-action problems, and the greater the inducements and punishments leaders will need to offer to compete.⁷⁹

The second factor relates to the level of uncertainty that exists in a civil war. Principal-agent problems are likely to be particularly problematic (and an extremist ideology particularly helpful) when rebel leaders and potential recruits have limited information about each other. This situation is likely to occur when a rebel group and its leaders are unknown to the local population, either because they originated outside the country or because they are operating far away from the individuals they seek to recruit. In both situations, rebel entrepreneurs must draw from a population with whom they have had limited contact and where local information networks are likely to be weak. Not only do leaders have less knowledge about the trustworthiness of individuals who volunteer for their organization, but local citizens have equally limited knowledge about which of the many emerging faction leaders is particularly well qualified to fight and win a war. Costly signals of dedication and trustworthiness from both leaders and recruits are likely to be particularly valuable under these circumstances.

The third factor is related to the level of institutional constraints on executive power. Commitment problems are likely to be acute for rebel entrepreneurs in countries where citizens know there is limited rule of law, few checks on government power, and endemic corruption. These are the civil wars in which citizens are likely to demand stronger commitments to good behavior over time in exchange for their support. An ideology that provides its own strict rules and laws, and its own mechanisms for justice, becomes quite useful under these circumstances.

These three conditions suggest that extremism will not emerge and thrive in all civil wars. Rebel groups that face limited or no competition for local support, that have deep local networks from which they can draw fighters, and that operate in a country with a strong rule-of-law tradition have far fewer incentives to move to the ideological extreme. These are the cases where the local population has little need for especially costly signals or credible commitments, and where they are more likely to gravitate toward moderate groups whose ideologies better match their own.

Seen in this light, the theory offers insights into the rise of Salafi jihadist groups in the post-2003 civil wars. According to the theory, when faced with the opportunity to compete for power, rebel entrepreneurs first choose ideologies likely to appeal to the needs and desires of a particular population. They then determine the group's level of extremism based in part on how severe collective-action, principal-agent, and commitment problems are likely to be.

Although not definitive, my theory suggests that the emergence of so many Islamist groups in recent years appears to follow this pattern. Political contestation in the Middle East began in earnest in 2003 with the fall of Saddam Hussein and expanded with the Arab Spring protests of 2010–11. These two events undermined the post–World War II imperial order and created an opening for political entrepreneurs to assert new visions for government and society. Not surprisingly, every rebel group that subsequently formed in the region embraced political Islam (“Islamism”) as its main ideology.⁸⁰ As discussed above, large majorities of citizens in the Muslim world favor a prominent role for Islam in the political life of their countries, and political identity in the Muslim world has long been vested in religion rather than ethnicity.⁸¹ In addition, an Islamic form of government served as an attractive counterpoint to the corrupt, mainly secular regimes that had triggered the protests.

The question, however, is why so many groups chose to embrace a fringe form of Islamism rather than a more moderate one. According to the theory, rebel entrepreneurs have incentives to move to the ideological extreme when competition for new recruits is intense, when uncertainty about the dedication of rebel leaders and recruits is high, and in countries with weak political institutions and a history of bad governance. All three of these conditions existed in the Arab world when civil wars broke out.

The first distinguishing feature of the current wave of civil wars is the large number of Sunni factions fighting in each one. Four major Sunni factions are currently fighting in Syria, three in Iraq, three in Libya, two in Yemen, and three in Somalia (this does not include the many smaller Sunni factions that also exist).⁸² Sunni factions proliferated in these wars for at least three reasons. First, Sunnis represented the largest sectarian group in all but one of these countries (Iraq) and the largest group excluded from power in Syria and Iraq. Sunni citizens, therefore, had the greatest incentive to fight for political change. Second, Sunnis represent between 85 and 90 percent of Muslims worldwide, creating an exceptionally large pool of potential recruits from which rebel groups could draw. Third, Sunni-based rebel groups had the added opportunity to attract financing from wealthy Persian Gulf countries keen to install Sunni-led governments throughout the Middle East. Thus, the combination of large local Sunni populations, even larger global Sunni populations, and wealthy Sunni patrons made it possible for multiple political entrepreneurs to attempt to form their own separate factions.

The proliferation of Sunni rebel factions created heavy competition and, thus, incentives for some of them to embrace an extreme version of Sunni Islamism—Salafi jihadism. The usual collective-action problem associated with recruiting soldiers was exacerbated by the need to outcompete rival groups, making relatively costless inducements and punishments particularly important. Salafi jihadism's veneration of the “martyr” and its aggressive use of takfir were tools that less extreme groups did not have when vying for the same set of Sunni citizens.⁸³

So, why did citizens gravitate toward the most extreme of the extreme rebel groups (ISIS or Jabhat al-Nusra) when they could have opted for slightly less extreme groups such as Ahrar al-Sham, the Jaysh al-Fath coalition, or Jaysh al-Islam? Citizens could have gained similar benefits and reassurances from these competing groups, yet opted for the most extreme ideological choice. The reason, I argue, has to do with timing. ISIS and al-Qaida solved the collective-action problem earlier than these other groups, drew from a ready-made and more devoted external network of followers willing to grant financial and material support, and more rapidly coordinated effective strikes against the state. Thus, these groups appeared more capable at an earlier point in the war, consolidated power, and distinguished themselves from a field of similar-looking groups.⁸⁴

The second distinguishing feature of the post-2003 civil wars was the emergence of rebel groups with weak local connections. ISIS, for example, did not have deep roots in Iraqi or Syrian society, or in Libya, Mali, Nigeria, Somalia, or Yemen. In addition, all of the most extreme Salafi jihadist groups—al-Qaida in the Islamic Maghreb, al-Shabaab, al-Nusra, and ISIS—split from preexisting movements. These groups were second-movers in their respective civil wars, forced to play competitive catch-up with existing Sunni factions. Jabhat al-Nusra, for example, formed ten months after the uprising in Syria began.⁸⁵ In highly competitive environments, where little information is known about a new group, Salafi jihadism can provide a relatively quick and easy way to appeal to the most devoted citizens and potentially hardest fighters. In addition, recall that moderate citizens have incentives to support the group that is likely to win the war. Salafi jihadist groups start out weak but steadily grow stronger as they are able to recruit these dedicated and strong fighters. In so doing, they increase their appeal to more moderate citizens, who gain more information about the relative strength of competing groups as the war progresses.

A third distinguishing feature of these civil wars was the authoritarian nature of the incumbent regimes and the absence of the rule of law in each of the affected countries. The weak political restraints on Arab leaders and the extraordinary corruption with which they ruled created severe commitment problems for rebel leaders claiming to seek to serve the Sunni population. It is no coincidence that an ideology that emphasized morality and justice emerged in a region that had been dominated by repressive and shockingly bad governments.

Salafism promised to represent Islam in all its purity. One of the foundational beliefs of this ideology is that adherents should live like their “pious predecessors”—those who lived prior to any Western interference or corruption in the region. The call for a return to early Islamic heritage was a call for a return to values that have disappeared in the modern era of despotism, patrimonialism, and bad government.⁸⁶ ISIS won followers by promising to establish a theologically authentic state rather than a modern political one. According to one expert, “It is the group's doctrinally consistent bypassing of Western political culture that has allowed it to pick up so many recruits.”⁸⁷

In addition, war destroyed any semblance of law and order, making the Salafi jihadist groups even more attractive to moderate citizens as violence and disorder progressed. This helps explain why Salafi jihadists in Iraq and Syria gained adherents in the midst of war and why they remained militarily relevant much longer than their moderate rivals. War dramatically reduced what few institutions existed and offered an advantage to those groups who could best promise and deliver order and justice.

Did the same occur on the Shia side? Although Shia factions proliferated, especially in the Iraq civil war, these groups did not move to the ideological extreme to the same degree as did Sunni factions. The same is true of the Kurds in both Iraq and Syria. There are two reasons for this. First, the competition among Shia factions was not nearly as intense as it was among Sunni factions; dramatically fewer Shia factions formed in both the Iraq and Syrian civil wars. Shia rebel leaders, therefore, did not have the same incentives to shift to a more extreme version of Islamism because collective-action problems were not as severe. Second, Shia organizations in Syria and Iraq were homegrown, unlike their Sunni counterparts, which transcended international borders.⁸⁸ Shia factions, therefore, were not under the same burden to provide quick information about their dedication to the cause for which they were fighting.

In short, Salafi jihadism succeeded in winning over local populations because its particular ideology represented the sweet spot for the strategic use of extremism discussed above. First, Islamism tapped into the desire of the population for a more just political system based on religion.⁸⁹ Justice, honor, and a lack of corruption were the key ideals the ideology promoted and this mirrored the ideals sought by a majority of the population in Iraq, Libya, Syria, and Yemen. Second, Salafi jihadists helped citizens identify which of the many competing Sunni leaders was most likely to be devoted to this cause, notwithstanding their claims. In a highly competitive world of rapid change, citizens were looking to identify those leaders who had some chance to remain true to a just Islamic state. Finally, this extreme ideology addressed the concerns of more moderate citizens that leaders would become corrupt once in office. In weakly institutionalized environments with a history of corruption—especially those in which institutions were further degraded by war—citizens understood that leaders could not be held accountable once in power. The language of Islam had resonance with the population, while the extreme version of Salafi jihadism reassured the population that a more principled Islamic state might actually be installed.

If embracing an extreme ideology at a particular point in time is so beneficial, why have all groups fighting these civil wars not adopted Salafi jihadism? Many groups have increasingly adopted a more extreme version of Islamism over time. Figure 1 reveals that starting in the early 1990s, the number of Salafi jihadist groups active worldwide began to increase, with a particular surge in growth after the Arab Spring. This growth suggests that political entrepreneurs increasingly recognized the benefits of embracing an extreme version of Islam given current conditions, and progressively adopted it.

Still, not all groups have moved to the ideological extreme. As of 2016, 30 percent of all major militant groups in Syria, 50 percent of all major militant groups in Somalia, and 65 percent of all major militant groups in Iraq are not Salafi jihadist. Four reasons likely account for this.

The first reason is that ideology is not entirely changeable; not all groups can easily switch ideology to become more extreme. A group that desires to become Salafi jihadist must gain the support of clerics with an established radical interpretation of Islam compatible with Salafi jihadism. To do so, rebel leaders must first prove their internal devotion to the creed, something not all elites are willing to do. Osama bin Laden, for example, was credible in part because he was willing to adhere to a strict interpretation of everyday living prescribed by Salafist doctrine.⁹⁰ Thus, while rebel leaders may come to instrumentally prefer a different ideology as a result of wartime processes, not all groups can successfully adopt any ideology they wish.⁹¹

Second, rebel entrepreneurs understand that there are decreasing marginal returns for embracing the same ideology as the rest of the field. Once four Salafi jihadist groups exist in a given civil war, becoming the fifth Salafi jihadist group is less likely to lead to success. Rebel entrepreneurs, therefore, may have incentives to differentiate their group from a crowded field of Salafi jihadist groups by staking out a different ideological position. Ahrar al-Sham, for example, has made significant efforts to distinguish itself from more extreme groups since 2015. The more a rebel group can differentiate itself from other rebel groups, the less competition it will face, and the easier it may be to recruit its own unique set of soldiers and supporters.

Third, there are benefits for capturing and maintaining the middle ground in a crowded field of competing rebel factions. These rewards can come in many forms, including support from moderate foreign sponsors, such as the United States, or aid from moderate sympathizers unwilling to help more extreme factions.⁹² The Syrian rebel group Ahrar al-Islam pivoted from a more extreme jihadist brand toward ideological moderation in early 2015 in an effort to convince Turkey and the United States that the organization could serve as a palatable alternative to the regime of Bashar al-Assad.⁹³ Moderate groups may also be allowed to organize and operate within countries in ways that radical groups are not; governments may be more willing to tolerate them; and outside states may be more willing to endorse them. The Muslim Brotherhood in Egypt, for example, has succeeded and survived in large part because it has avoided the extremist label.

Fourth, there are at least three types of costs groups must pay to embrace an extreme ideology that some leaders might seek to avoid. For one, groups that adopt Salafi jihadism are more likely to be targeted in the United States' war on terror, creating a powerful enemy with which they must simultaneously battle. The leaders of Hayat Tahrir al-Sham—formerly known as Jabhat al-Nusra—for example, sought to rebrand themselves and distance their organization from al-Qaida in part to avoid U.S. air strikes.⁹⁴ Second, there is a short-term/long-term trade-off for leaders who embrace an extremist ideology. An extreme ideology could help elites achieve short-term organizational goals during a war, only to make a negotiated settlement more difficult over the long term. Extremist rebel groups are more likely to engage in acts of terror, which then make them less likely to be invited to the negotiating table.⁹⁵ They are more likely to experience splintering,⁹⁶ and their leaders could face retribution from true believers in their party for any concessions they make. Al-Qaida's leadership, for example, at times sought to limit its extremism but was unsuccessful because of more extreme subsidiaries.⁹⁷ The benefits of extremism in the midst of civil war, therefore, must be weighed against the challenges of extremism when trying to end a conflict and transition to peaceful political rule.

There are a number of different explanations for why rebel leaders might embrace an extreme ideology and why these groups might then attract more supporters during war than moderate groups. The first set of explanations emphasizes the intrinsic appeal of ideology. It is possible that Salafi jihadist groups have grown in number and influence because Muslim citizens have become more radical since 2003. The empirical evidence, however, does not appear to support this. Surveys by the Pew Research Center found that Muslim views of ISIS are overwhelmingly negative. Ninety-nine percent of Muslims in Lebanon, for example, said that they had “an unfavorable opinion of the Islamic militant group in Iraq and Syria known as ISIS.”⁹⁸ It is also possible that the act of fighting a war serves to polarize a population, making citizens more likely to shift to the ideological extreme as the war progresses. If this were the case, then citizens would gravitate toward more extreme groups, not for any practical reason, but because their beliefs have become more extreme over time.

Also, it is possible that elites embrace Salafi jihadism not because of any organizational advantages, but because they are able to tap into the preestablished network created by al-Qaida and funded by wealthy Gulf states. Zarqawi, for example, clearly understood that aligning his Sunni rebel group, Jamaat al-Tawhid wal-Jihad, with al-Qaida in Iraq in 2001 would gain him access to al-Qaida's network of private Gulf funders, operational expertise, and recruitment mechanisms. Finally, it is possible that extremist groups have thrived because they are willing to engage in more brutal tactics than moderate groups, allowing them to outcompete rival groups in terms of coercion.

All of these explanations are plausible, and some almost certainly played a role in the rise of radical Islamist groups in Muslim countries around the world. The value of this article, however, is to point out that an extreme ideology can still have great value even if none of these other factors is at play.

This article helps to explain one of the major international phenomena of our time: the rise of Salafi jihadist groups in civil wars in the Muslim world. It began with the observation that the number of Salafi jihadist groups fighting in civil wars has grown and, in many cases, these groups have outperformed and outlasted more moderate groups. By 2016, Salafi jihadist groups accounted for most of the militant groups in Syria, half of all such groups in Somalia, and a third of all militant groups in Iraq.

Currently, the scholarly literature has no theory for why rebel groups would embrace an extreme ideology or why more extreme groups would perform better than more moderate groups in war. The academic literature has tended to ignore the role of ideology in civil war.⁹⁹ Instead, scholars have assumed that the core features of rebel groups—their identity, goals, and beliefs—were exogenous to the war in which they were fighting and not part of an ongoing strategy of the war itself.

This article has attempted to fill this gap. It has argued that the choice of ideology, especially the level of extremism, is likely to be endogenous to specific features of a civil war: the level of competition, a group's local support network, and the institutional constraints on state power. When competition is high, information poor, and institutional constraints weak, an extremist ideology could help rebel groups mitigate difficult collective-action, principal-agent, and commitment problems. An extremist ideology, therefore, can give rebel entrepreneurs an organizational advantage under certain conditions. All three of these conditions were present in the post-2003 civil wars in Muslim countries, and all help explain the emergence and growth of Salafi jihadist groups.

This theory challenges a number of assumptions about extremist ideology and its adherents. The popular press is filled with stories about the increasing radicalization of Muslims around the world. The assumption is that Salafi jihadism has grown in popular support and strength because the number of true believers has grown. This article offers a different interpretation of the rise of these groups. Muslims need not believe in an extreme version of Islam to sympathize and support groups that embrace such a vision. They need only operate in a world where political power is heavily contested and the quality and commitment of competing rebel groups is uncertain. An extremist ideology will always attract citizens who believe in the ideology, but during times of uncertainty and insecurity it will attract more moderate citizens as well.

Finally, the popular press often portrays individuals who join or collaborate with extremist groups as either true believers or hapless victims. The formation of so many Salafi jihadist groups and the ability of groups such as Jabhat al-Nusra, ISIS, and al-Qaida to capture and administer territory suggests a deeper level of local support than many Westerners have been willing to acknowledge. This article reveals the very practical incentives that moderate citizens might have to support such groups in environments of uncertainty, competition, and state abuse of power. The seeming popularity of Salafi jihadist groups, therefore, may have less to do with the ideas Salafi jihadism promotes than with the security and assurances it offers.

The framework reveals the role that an extreme ideology can play in organizing a rebel group and fighting a war. It suggests that many rebel leaders may have embraced Salafi jihadism because this particular ideology allowed them to use cheap inducements and punishments to attract supporters. The extreme nature of the ideology helped them recruit a core group of particularly tough fighters—zealots—who elevated the quality of the fighting force and helped enlist additional soldiers attracted to the success of the group. Salafi jihadism then allowed rebel elites to reassure Muslims that they would remain true to the rule of Islam and avoid aligning with the West, making them additionally attractive to a more mainstream audience. Al-Baghdadi and al-Zarqawi effectively used these advantages to outcompete other Sunni groups.

This article is the first step in understanding the role that ideology, especially extremist ideology, plays in civil war. It reveals the incentives that individuals may have to promote an extreme ideology even if they do not believe in its ideals. Much more work needs to be done. On the theoretical side, significantly more analysis is needed on the societal bases of ideology and on the initial choice of ideology by rebel entrepreneurs. Why do certain ideas resonate more with some societies than others? Additional theorizing is also needed on the strategic choices made by individual citizens and the conditions under which their support for one ideology over another may change and evolve over time.

On the empirical side, this framework lends itself to rigorous testing. The theory proposes a number of conditions purported to encourage the emergence of extremist rebel groups. These include periods of heavy political competition, low information, and weak political institutions. It also identifies additional factors that could cause elites and citizens to embrace an extreme ideology, including rapid social change, lengthy civil wars, and powerful Salafi jihadist networks. At the macro level, data could be collected on each of these variables to determine whether extremist groups are more likely to emerge under any of these conditions. At the meso level, data could be collected to determine whether the ideology of rebel groups fighting in a civil war changes as conditions on the ground change. Do rebel groups shift to more extreme ideologies if the number of rebel groups increases over time, or if financing from radical organizations suddenly becomes available? Finally, at the micro level, data could be collected to determine whether moderate citizens are strategic, shifting their support to more radical groups based on certain predicted conditions on the ground. Do moderate individuals behave as the theory predicts or are they more heavily influenced by other factors? It is my hope that this article triggers a larger research program on ideology and civil war that addresses many of these theoretical and empirical issues.

The theory, if correct, could have three potentially important implications for policymakers seeking to counter the rise of radical Islamist groups around the world. The most important concerns the sources of support for extremist groups, especially from local populations. The type of counterstrategy the United States pursues will depend heavily on whether U.S. leaders assume that Muslim citizens support Salafi jihadist groups because they truly believe in a seemingly “medieval” and fringe interpretation of Islam, or because they believe these groups are more likely to deliver justice and reform in countries where both characteristics are missing. This article reveals the incentives that moderate citizens may have to support extreme groups and the conditions under which these incentives are likely to be strong and weak. It also reveals the parts of an extremist strategy that are designed to appeal to more moderate citizens. Dissuading true believers from joining these movements will be a huge challenge, but convincing more moderates to defect might not.

This article suggests three ways in which moderate support for these movements might be undercut. The first involves the competitive nature of these wars and the collective-action problems this creates for rebels. Wars with multiple competing rebel factions create incentives for rebel entrepreneurs to go to the ideological extreme, but this competition also creates opportunities for outsiders to bolster less extreme groups. This can be done by helping moderate groups build high-quality fighting units that would then attract the support of a larger percentage of moderate citizens. The second has to do with agency problems. Outsiders can also help to reveal the fraudulent nature of extremist elites and their claims. Religious authorities of a more moderate persuasion (often tribal leaders), for example, can use the politics of religious legitimacy as a check against radical leaders who attempt to use their religiosity as a costly signal of principle and devotion. Finally, outsiders can address the commitment problems that encourage extremism by helping to reform state institutions and refusing to support and sustain corrupt regimes.¹⁰⁰

Scholars can no longer close their eyes to the role of ideology in civil war. The rise of Salafi jihadist groups, with their global aims and their condemnation of the United States and its allies, has become one of the biggest security threats in the world today. To date, the United States has not been particularly effective at reducing their number. Indeed, these groups are growing over time. This growth suggests an underlying level of support from Muslim communities around the world that we do not yet understand. Only by analyzing the ways in which an extreme ideology may benefit both elites and more moderate citizens in civil war can we begin to understand how it might be strategically used, and the conditions under which it is likely to attract support. This article is a first step in that direction.

The author thanks Jesse Driscoll, Isaac Gendel, Dotan Haim, Ron Hassner, Allison Hodgkins, Joshua Kertzer, Aila Matanock, William McCants, Assaf Moghadam, Richard Nielsen, Emily Ritter, Michael Stohl, and Keren Yarhi-Milo for their willingness to read the manuscript and offer helpful feedback. She is especially grateful to Gregoire Phillips for answering an endless series of questions with enormous good cheer. Finally, she thanks the participants of the International Relations Faculty Colloquium at Princeton University for inviting her to present this work and following up with thoughtful suggestions.