Deterring Terrorism: a New Strategy

Deterring Terrorism: a New Strategy

by Max Abrahms


Terrorists are poor candidates for deterrence. They are difficult to deter because they are motivated by a wide variety of personal and strategic aims. The diversity of these aims practically ensures that many terrorists will derive utility from their actions regardless of how governments respond. In fact, even opposite government responses tend to generate utility for terrorists due to the complexity of their incentive structure. To an extent, however, terrorism may still be deterred by dissuading terrorist supporters since they are critical for mounting large-scale terrorist campaigns. Compared to terrorists, their supporters are more deterrable due to the relative simplicity of their incentive structure. People generally support terrorists for a single reason—to achieve their political demands. Fortunately, a growing body of empirical research finds that terrorism is a losing tactic for perpetrators to induce major concessions from governments. The policy community can help to deter terrorism by teaching its supporters about the tactic’s politically counterproductive effects. 

Keywords: deterrence, counter-terrorism



Traditional concepts of deterrence try to thwart unwanted behaviour by manipulating adversary incentives. Deterrence-by-punishment threatens to impose costs on the adversary for an undesirable course of action. Deterrence-by-denial seeks to deny him any benefits from it.[1] Clearly, both strategies are based on influencing the adversary by reducing the utility of his actions. Unfortunately, neither approach is likely to succeed since terrorists are generally motivated by such a wide variety of personal and strategic aims that they are liable to derive utility from their actions regardless of how governments respond.

Although traditional concepts of deterrence are unlikely to work against terrorists on any systematic basis, the tactic itself may be deterred with an alternative counterterrorism approach. Deterrence-by-delegitimisation focuses less on deterring adversaries themselves than their support constituencies.[2] This less well-known indirect form of deterrence offers superior counterterrorism promise because terrorist supporters are more likely to be motivated by a relatively straightforward incentive structure. Unlike the perpetrators themselves, their supporters are generally driven by one main goal—the desire to coerce government concessions. In recent years, a growing body of academic research has found that terrorism decreases rather than increases the odds of government compliance. In this fundamental sense, the tactic of terrorism is politically counterproductive. The policy community’s primary contribution to deterring terrorism should be to broadcast this finding in a targeted public diplomacy campaign to terrorist supporters.

The argument of this article proceeds in three sections. In the first section, an explanation is offered why classic concepts of deterrence are doomed to fail against terrorists. The strategies of deterrence-by-punishment and deterrence-by-denial are based on the unrealistic premise that governments can deter terrorists by simply removing the utility of their violent behaviour. This assumption is faulty not because terrorists are categorically irrational actors, but because they do not employ a uniform, consistent metric of success. Indeed, many terrorists seem to regard their actions as fruitful regardless of how governments choose to respond. The second section argues that most terrorism is deterrable, however, even if its practitioners are not. This section details the burgeoning academic literature on terrorism’s political ineffectiveness and explains how this finding can be exploited to deter terrorist supporters and, by extension, the tactic itself. The conclusion issues an appeal to the policy community—work closer with the academic community on counterterrorism. Only by sharing our knowledge can we hope to deter the terrorism threat.


Why Terrorists Tend to Be Undeterrable

The conventional approaches to deterrence are actually two sides to the same coin. In deterrence-by-punishment, the threat of reprisal is intended to deter the adversary with unacceptable costs. In deterrence-by-denial, the point is to deter him by removing the potential value of his actions. As Matthew Kroenig and Barry Pavel noted: “Whereas cost imposition strategies threaten retaliation, benefit denial strategies threaten failure. If actors believe that they are unlikely to succeed or reap significant benefits from a certain course of action, they may be deterred from taking it.”[3] When it comes to combating terrorism, however, this objective is intractable because its practitioners seem to derive value from their actions notwithstanding the nature of the government response.

Nowhere is this clearer than in Andrew Kydd and Barbara Walter’s pioneering study on terrorist motives. [4] In “Strategies of Terrorism,” Kydd and Walter report that terrorists are motivated both to coerce government concessions and to provoke government retaliation. Left unsaid is that these government responses are essentially opposites. Terrorism succeeds as a coercive strategy when governments appease the perpetrators by accommodating them with concessions. Conversely, terrorism succeeds as a provocation strategy when governments dig in their political heels and go on the offensive. If Kydd and Walter are correct, then terrorism offers strategic utility to many perpetrators whether governments act conciliatory or not.

The empirical record is replete with evidence that terrorists are indeed motivated by such inconsistent strategic objectives. Members of al-Qaeda and its affiliates, for example, emphasize in public pronouncements that coercing government concessions is an important strategic objective. Al-Qaeda has historically called on the United States to withdraw militarily from the Muslim world and to sever relations with apostate regimes.[5] Al-Qaeda affiliated members have also emphasized these foreign policy goals in private. In October 2001, for instance, a trove of letters written by Osama bin Laden was seized by Scotland Yard.  The objectives listed in the letters repeat the coercive goals of driving out U.S. forces from the Muslim world and ending U.S. interference in Muslim politics. [6] Surely, al-Qaeda would declare victory if Washington were to accede to such political demands.

Yet al-Qaeda has an equally rich tradition of trying to elicit the opposite government response. Al Qaeda military leader, Sayf al Adl, said the main goal of 9/11 was not to coerce the U.S. from the Muslim world, but to provoke American military operations there. According to al Adl, President George W. Bush played into this strategy by pursuing the “anticipated response” in Afghanistan, Iraq, and other Muslim countries. In a May 2005 statement, he explained: “What we had wished for actually happened.”[7] Similarly, bin Laden often said the purpose of 9/11 was “for us to provoke and bait this administration.”[8] More recently, Ayman al-Zawahri praised operatives for “provoking” the United States into adopting costly counterterrorism responses at home and abroad.[9] These public pronouncements accord with al-Qaeda’s private statements. In autumn 2001, for instance, a journalist visiting Afghanistan famously recovered Zawahiri’s personal computer with hundreds of correspondences to bin Laden, Khalid Sheikh Muhammad, and other 9/11 planners. These correspondences make clear that the al-Qaeda leadership was unworried about provoking a U.S. invasion of Afghanistan. In fact, they hoped the U.S. would respond in that fashion and then get bogged down in a costly asymmetric conflict.[10]

To gain insight into how al-Qaeda evaluates strategic success, Abrahms and Lula conducted a content analysis of bin Laden’s translated statements made in public and private between 1994 and 2004.[11] Collated by the Foreign Broadcast Information Service, this self-contained compilation of 98 interviews, correspondences, and fatwas is believed by counterterrorism officials to provide reliable insight into al-Qaeda’s strategic mindset during that period.[12] The authors examined the asymmetric campaigns exalted by bin Laden Osama as political successes and then categorised them. According to the al-Qaeda leader, the most successful asymmetric campaigns included cases in which the target country was coerced into making accommodations or provoked into adopting the opposite response. 

These competing goals of coercion and provocation are hardly confined to al-Qaeda. In fact, they are strategic objectives found across numerous terrorist groups.[13] So, too, are other strategic goals that are equally difficult to reconcile. A common terrorist strategy, for example, is “spoiling” peace processes by ramping up violence during negotiations in order to halt them in their tracks. Whereas coercion is intended to induce politically conciliatory behaviour and provocation is intended to elicit the opposite political response, spoilers seek to destroy any peaceful political movement at all.[14] Scholars may be tempted to conclude that terrorists are thus irrational. The point, however, is that many terrorists are able to derive utility from their actions regardless of how governments respond due to the complexity of their incentive structures. Terrorists are often able to accomplish at least some of their core strategic aims when governments retreat, advance, or do nothing at all. Since almost any conceivable response is liable to generate strategic utility from the vantage of terrorists, they are decidedly poor candidates for deterrence.

In fact, the byzantine strategic goals of terrorists only partially account for their complex incentive structure. People participate in terrorism for an even wider range of personal goals than strategic ones. The personal benefits of participating in terrorism are hardly affected by the nature of government reactions. Research shows, for example, that terrorists are often motivated by the social benefits of participating in a tight-knit group independent of any political progress.[15] For this reason, terrorists routinely reject compromise proposals, eschew superior political tactics, and fight rival groups sharing their given ideology. Such terrorist behaviours may not be politically instrumental. Yet each generates utility for those members who are motivated by the social solidarity of participating in a terrorist group and therefore wish to perpetuate it.

Participating in terrorist groups also supplies members with countless personal benefits beyond social solidarity. For many terrorists, perpetrating the violence helps to give them purpose, end their boredom, facilitate travel to new destinations, gain respect, follow their religious convictions, terminate their miserable lives, or simply harm and frighten others. In the early 1990s, many policy-makers began to recognize that the conventional understanding of terrorist groups needed revision. Whereas past terrorists seemed motivated to achieve their given strategic objectives, the “new terrorists” are increasingly defined by their questionable attachment to them. Since the 1990s, the international terrorism threat has been driven by perpetrators aiming to kill the maximum number of civilians, perhaps as an end in itself. A 1995 National Intelligence Estimate observed that the 1993 World Trade Center bombing was intended “to kill a lot of people, not to achieve a more traditional political goal.”[16] Former CIA director James Woolsey similarly noted that “Today’s terrorists don’t want a seat at the table; they want to destroy the table and everyone sitting at it.”[17] Ashton Carter, John Deutch, and Philip Zelikow expanded on this interpretation in a 1998 article in Foreign Affairs, writing that the new wave of “catastrophic terrorism” is not designed to affect policy, but to create destruction in itself.[18] This macabre incentive among international terrorists blossomed after the 9/11 attacks. When news first reached bin Laden and his lieutenants of the human consequences, they were reportedly elated while though the Bush administration was still debating how to respond.[19] For al-Qaeda leaders, the nature of the U.S. response was secondary if not wholly inconsequential because the bloodshed alone was already cause for jubilation.

But just because terrorists rejoice from an operationally successful attack, this does not mean they can be deterred with a denial strategy. Denying terrorists from carrying out operationally successful attacks is a losing strategy for two main reasons. First, terrorists are manifestly motivated by numerous goals, some of which do not even require attacks at all.[20] Second, a consensus exists within the policy community that terrorists will always finds ways to mount operations, given sufficient resolve. As Stephen Flynn remarks, terrorism “will be perennially in the offing” because “it is an ongoing hazard, something we will never successfully eliminate.”[21] This is true for several reasons. For terrorists, potential targets include anywhere people gather. As such, very little capability is required for carrying out an attack. In the rare cases where targets are effectively hardened, terrorists simply move on to softer targets. Governments may try to play cat and mouse, but are ultimately constrained in their responses particularly within democracies.[22] In sum, the ease of perpetrating attacks virtually guarantees some form of success though is hardly a requirement for it.  

For the sake of prediction, scholars tend to model the behaviour of terrorists by attributing to them simple, straightforward incentive structures. In their efforts to achieve parsimony, however, these models are often too reductive. The evidence suggests that terrorists tend to harbour varied, complex, even inconsistent strategic and personal aims. Given the complexity of their objectives, terrorists seemingly derive utility from their actions regardless of how governments respond. The inability of governments to reduce the utility of terrorism seemingly presents an insurmountable challenge for deterring its practitioners.


Deterring Terrorist Support

It would be easy to conclude that terrorism cannot be deterred because its practitioners are fundamentally undeterrable. In fact, counterterrorism circles are heavily populated by deterrence naysayers. Richard Betts, for example, contends that deterrence has “limited efficacy…for modern counterterrorism.” Paul Davis and Brian Michael Jenkins likewise assert, “The concept of deterrence is both too limiting and too naïve to be applicable to the war on terrorism.” And President George W. Bush’s National Security Strategy concluded, “Deterrence will not work against a terrorist enemy.”[23] This pessimistic outlook is unwarranted. Terrorism may be deterrable even though most of its practitioners are not.

Unlike the strategies of deterrence-by-punishment and deterrence-by-denial, deterrence-by-delegitimisation does not seek to deter the perpetrators themselves. Rather, deterrence-by-delegitimisation aims to deter unwanted behaviour by discrediting the perpetrators in the eyes of their supporters. For counterterrorism purposes, this means our focus should be on deterring terrorist supporters by discrediting the perpetrators. This approach has a large, untapped strategic upside for three main reasons.

First, the ability of terrorists to generate violence depends critically on their level of support. There is indeed power in numbers for producing terrorism.[24] When support from the local population grows, so too does the terrorism threat since its perpetrators are then better equipped to elude authorities and acquire material resources essential for sustaining full-fledged terrorist campaigns.[25] Admittedly, even isolated terrorists are able to inflict some measure of pain because terrorism is the proverbial weapon of the weak. But shrinking the pool of supporters would go a long way towards curbing terrorism since it enfeebles its perpetrators.

Second, supporters of terrorism are potential candidates for deterrence due to the relative simplicity of their incentive structure, which facilitates the manipulation of costs and benefits undergirding the deterrence mechanism. In marked contrast to terrorists, their supporters tend to be motivated by one main goal—achievement of the terrorist group’s political demands. International polls consistently show that when terrorism is seen as strategically advantageous, public support for the perpetrators increases. But when terrorism is viewed as strategically disadvantageous, public support decreases. Al-Qaeda in Iraq is an illustrative example, as local support for it dried up once its attacks were seen as politically costly. Similarly, Palestinian support for Hamas and other terrorist groups in Israel is positively related to perceptions of  political effectiveness. When terrorism is viewed as an impediment to Israeli concessions, the Palestinian public invariably turns against the perpetrators, effectively isolating them.[26]

Third, terrorist supporters are deterrable because they systematically overestimate the political value of terrorism. In recent years, a growing body of empirical research has found that terrorism does not actually help the perpetrators to coerce major government concessions. Terrorism is not simply highly correlated with political failure; the tactic appears to have an independent, negative impact on the odds of government concessions. Terrorism can therefore be deterred by educating its supporters about the harmful effects to their political preferences. Below, is a summary of the existing research landscape on terrorism’s political impact. Across several methodologies, the evidence indicates that terrorism is a losing political tactic that hampers perpetrators from obtaining their demands.

Terrorism is usually defined as non-state attacks against civilian targets for a putative political purpose.[27] This combination of target selection and objective is, however, in tension. For decades, specialists have noted that terrorism almost never results in strategic concessions. In the 1970s, Walter Laqueur published “The Futility of Terrorism” in which he asserted that perpetrators seldom manage to wring important government concessions.[28] In the 1980s, Bonnie Cordes, Bruce Hoffman, and Brian Jenkins likewise observed, “Terrorists have been unable to translate the consequences of terrorism into concrete political gains…[I]n that sense terrorism has failed. It is a fundamental failure.”[29] Martha Crenshaw also pointed out, “Few [terrorist] organisations actually attain the long-term ideological objectives they claim to seek, and therefore one must conclude that terrorism is objectively a failure.”[30] In the 1990s, Thomas Schelling proclaimed, “Terrorism almost never appears to accomplish anything politically significant.”[31] Sun-Ki Chai remarked that terrorism “has rarely provided political benefits” at the bargaining table.[32] Virginia Held went even further, claiming that the “net effect” of terrorism is politically counterproductive.[33] Since the September 11 attacks, a series of large-n studies has confirmed that only a handful of terrorist groups in modern history have accomplished their political platforms.

In 2006, Max Abrahms published in International Security an article entitled “Why Terrorism Does Not Work”; the first large-n study on terrorism’s political effectiveness.[34] The effectiveness of terrorism can be measured in terms of its process goals or outcome goals. Process goals are intended to sustain the terrorist group by attracting media attention, scuttling organisation-threatening peace processes, or boosting membership and morale often by provoking government overreaction. The outcome goals of terrorists, by contrast, are their stated political ends, such as the realization of a Kurdish homeland, the removal of foreign bases from Greece, or the establishment of Islamism in India. An important difference between process goals and outcome goals is that unlike the former, the latter can only be achieved with the compliance or collapse of the target government. The study assessed whether terrorism helps militant groups to achieve their outcome goals, that is, their core strategic demands. To this end, Abrahms analysed the political plights of the twenty-eight Foreign Terrorist Organisations (FTOs), as designated by the U.S. State Department. The analysis yields two main findings. First, the FTO success rate is quite low—under ten percent—compared to other non-state tactics. On average, the FTOs perpetrated terrorism for decades without any visible signs of political progress. Second, and even more importantly, the successful FTOs used terrorism only as a secondary tactic. FTOs are just like other militant groups that exhibit wide variation in their tactical choices. All of the political winners directed their violence against military targets, not civilian ones. By disaggregating the FTOs by target selection, Abrahms helped to reveal the full extent to which terrorism—defined as non-state attacks against civilian targets—has historically been a losing political tactic.

Subsequent studies have found even lower rates of terrorist success. Seth Jones and Martin Libicki examined the universe of known terrorist groups between 1968 and 2006. Of the 648 groups identified in the RAND-MIPT Terrorism Incident database, only 4 percent obtained their strategic demands.[35] More recently, Audrey Cronin reexamined the success rate of these groups, confirming that less than 5 percent prevailed.[36] Suicide terrorism is usually more lethal than the conventional type, but its practitioners fail at an even higher rate.[37]

These low figures actually exceed the coercion rate, however, as terrorists may accomplish their demands for reasons other than civilian pain. In fact, all of the studies emphasize that terrorism does not encourage concessions. In his 2006 study, Abrahms concluded that “the poor success rate is inherent to the tactic of terrorism itself.”[38] Jones and Libicki contend that in the few cases in which terrorist groups have triumphed, “Terrorism had little or nothing to do with the outcome.”[39] And Cronin observes that the victorious have achieved their demands “despite the use of violence against innocent civilians [rather] than because of it,” and that “The tactic of terrorism might have even been counterproductive.”[40] Hard case studies have inspected the limited historical examples of clear-cut terrorist victories, determining that these salient events were idiosyncratic, unrelated to the harming of civilians, or both.[41]

The tactic does not appear to be epiphenomenal to government intransigence or the result of selection bias. On the contrary, the latest wave of scholarship provides a raft of evidence that escalating violence against civilians impedes non-state challengers from attaining their demands. To demonstrate the political ineffectiveness of terrorism, Abrahms published in Comparative Political Studies a coercion study that scrutinised the political outcomes of 125 FTO campaigns. The study reveals substantial variation in the political success of Foreign Terrorist Organisations depending on their tactical choices. Evidently, FTOs are significantly more likely to coerce government compliance when their violence is directed against military targets instead of civilian ones—even after controlling for the capability of the perpetrators, the nature of their demands, and many other tactical confounds.[42] Virginia Fortna analysed the coercive effectiveness of terrorism within civil wars. After factoring out the relative capabilities of rebel groups, she found they are also more likely to coerce government compliance by refraining from terrorism.[43] Similarly, Anna Getmansky and Tolga Sinmazdemir found that the Israeli government in particular is significantly less likely to cede land to the Palestinians when they have perpetrated terrorism. The authors exploit variation in the operational outcome of terrorist attacks and find that “successful” ones actually prompt Israeli land seizures rather than territorial concessions.[44] Relatedly, Erica Chenoweth and Maria Stephan found that protest groups suffer at the bargaining table when they employ violence against the population.[45] The same is true for militant groups that seize hostages. Militant groups are far more likely to successfully pressure government compliance when they refrain from harming the hostages, particularly civilian ones.[46] With few exceptions, coercion studies thus find that terrorism lowers the likelihood of government concessions.[47]

Terrorism rarely frightens citizens of target countries into supporting more dovish politicians. On the contrary, studies on public opinion demonstrate that terrorist attacks tend to raise popular support for right-wing leaders opposed to appeasement. Based on their dataset of Palestinian attacks from 1990 to 2003, Claude Berrebi and Esteban Klor found that terrorism boosts national support for right-wing parties in Israel, such as the Likud.[48] In a related study, the authors demonstrate that Israeli localities struck by terrorism gravitate to right-bloc parties opposed to territorial concessions.[49] Eric Gould and Estaban Klor also explored geographic variation in terror attacks within Israel and found that the bloodiest ones are the most likely to induce this rightward electoral shift.[50] Anna Getmansky and Thomas Zeitzoff found that Israelis within range of rocket-fire from the Gaza Strip are significantly more likely to support right-wing candidates.[51] These trends appear to be the international norm, not Israeli specific. Christophe Chowanietz analysed variation in public opinion within France, Germany, Spain, the United Kingdom and the United States from 1990 to 2006.[52] In each target country, terrorist attacks have shifted the electorate to the political right in proportion to their lethality. Related observations have been registered after al-Qaeda and its affiliates killed civilians in Egypt, Indonesia, Jordan, the Philippines, Russia, Turkey, and the United States.[53] RAND observes in a précis of the literature: “Terrorist fatalities, with few exceptions, increase support for the bloc of parties associated with a more intransigent position. Scholars may interpret this as further evidence that terrorist attacks against civilians do not help terrorist organisations achieve their stated goals.”[54] By bolstering hardliners, militant groups engaged in terrorist attacks are more likely to be crushed from the backlash they provoked.[55]

To understand why terrorism is a suboptimal instrument of coercion, it is useful to review how this violent tactic is supposed to work in the first place. In theory, terrorism operates as a political communication strategy that signals to the target country the costs of noncompliance; terrorism allegedly coerces government accommodation when the expected cost of the violence against civilians exceeds the expected cost of making the concession.[56] This bargaining logic lacks external validity, however; in fact, terrorism is a poor coercive tactic precisely because it is a flawed communication strategy.

Content analyses of media stories strongly suggest that terrorism struggles to amplify terrorist demands. Michael Kelly and Thomas Mitchell have produced the most ambitious study on the media’s coverage of terrorist demands. Their content analysis of terrorism articles in the New York Times and Times of London reveals that historically “less than 10 percent of the coverage in either newspaper dealt in even the most superficial way with the grievances of the terrorists”[57] Terrorists are unable to broadcast their demands even when the perpetrators emphasise them, are highly educated, and speak the majority language of the target country. As Alex Schmid and Janny de Graaf illustrated  in the case of the American Weather Underground, “The terrorists could bomb their names on to the front pages, but they could do next to nothing to make sure that the message intended by their bombings was also the message transmitted.”[58] In her analysis of European-based terrorist groups, Bonnie Cordes et al. likewise find that “The violence of terrorism is rarely understood by the public.”[59] Kelly and Mitchell go even further, noting the use of terrorism seems to “sap…its political content.”[60] Anecdotal evidence thus abounds that terrorism is a losing political tactic because it is a poor communication strategy.

In a recent study published in International Studies Quarterly, Abrahms proposed and tested a new psychological theory to explain why terrorism underperforms politically. The Correspondence of Means and Ends bias is a newfound cognitive heuristic in international relations. It posits that citizens of target countries are apt to infer the extremeness of the perpetrators’ political preferences directly from the extremeness of his tactics. That is, terrorists are seen as harbouring extreme, unappeasable ends because of their use of extreme means. Because of this human tendency to confound the extreme means of the perpetrator with his presumed ends, escalating to terrorism or other violent tactics can discredit him as a viable negotiating partner.[61]

To test the Correspondence of Means and Ends bias, Abrahms conducted an online experiment on a large, representative national sample of American adults. All subjects were presented with a simple vignette of an unidentifiable group issuing a traditionally moderate preference through the American media—the release of its imprisoned leaders from U.S. custody in exchange for permanently demobilising. Subjects were randomly assigned, however, to two conditions that differed along a tactical dimension. In the control condition, the group surrounds a bunch of American civilians, takes them hostage, but does not physically harm anyone in the course of the confrontation. The same information was presented in the treatment condition, except the group escalates tactically by killing the civilians in its custody. To minimise framing issues, the survey instrument paid attention to the formal aspects of the instrument by avoiding any derivatives of the word terror or any other emotive labels to describe either the coercive acts or the actors themselves. The two conditions were thus duplicates, except in the painful treatment the moderate group adopts a more extreme method by killing the civilians instead of releasing them unharmed.

Subjects in both conditions were presented with a series of identical multiple choice and ordinal scale questions designed to assess both directly and indirectly the perceived extremeness of the group’s preferences. Specifically, all subjects were asked the following set of questions: (1) to evaluate whether the group is motivated to achieve its demand of freeing the imprisoned leaders in U.S. custody or to harm Americans out of hatred towards them; (2) to rate the group’s preferences from 1 to 7 along this continuum;[62] (3) to judge whether the group would in fact demobilise upon achieving its demand to free the imprisoned leaders; (4) to appraise whether the group would derive satisfaction from Americans physically harmed in an unrelated incident that would not contribute to winning back the imprisoned leaders in U.S. custody; and (5) to ascertain whether the group would continue to engage in the same actions against Americans even after discovering a less extreme method that promised to free the imprisoned leaders.

Following a standard convention in experimental research, Abrahms then applied a two-tailed difference of means test to determine whether the tactical manipulation alone yields significant variation in the perceived extremeness of the self-described moderate group’s preferences. Answers to each of the five questions are statistically significant at the .01 level or better. Compared to subjects in the control condition in which no civilians were physically harmed, those exposed to the painful treatment were on average: (1) 27 percent more likely to believe the group is motivated not to free the imprisoned leaders in U.S. custody, but to harm Americans out of hatred towards them; (2); 20 percent more likely to rate the group’s preferences as the most extreme on a standard 7-point ordinal scale;[63] (3) 23 percent more likely to believe the group would not demobilise upon achieving its demand to free the imprisoned leaders; (4) 33 percent more likely to believe the group would derive satisfaction from Americans physically harmed in an unrelated incident that would not contribute to winning back the imprisoned leaders; and (5) 22 percent more likely to believe the group would continue to engage in the same actions against Americans even after discovering a less extreme method to free its leaders from U.S. custody. The experiment therefore helps to resolve why governments dig in their political heels in the face of terrorism. When groups escalate to this extreme tactic, they are seen as harbouring equally extreme political preferences, undermining confidence in negotiating with them.

For experimentalists in psychology or behavioural science, the quality of a causal mechanism depends less on the scope of confirming cases than on the theoretical construct and its predictive power. As a robustness check, however, the study also tested the mechanism with another vignette, again varying only whether the moderate group escalates tactically by killing the hostages instead of releasing them unscathed. Subjects in both conditions were presented with the same set of questions to further assess whether the extremeness of tactics employed by non-state actors informs perceptions of their preferences independent of their actual demands. Across questions, those exposed to the painful treatment were again significantly (p<.01) more likely to conclude that the perpetrators are motivated to harm the population irrespective of whether the moderate demand were granted.

Figure 1: Average Survey Responses for Painful Treatment and Painless Control (Vignette 1)

1.   Group hates Americans and wants to harm them.
4.   Group would gain satisfaction from Americans harmed in unrelated incident.
2.   Group is most extreme on 7-point scale. 5.   Group would continue to do same actions upon discovering less extreme tactic to achieve its demand.
3.   Group would not demobilize upon achieving demand.  


Description: Max-gray-chart

This is the first controlled experiment on the mechanism of coercion. A concern inherent to this methodology is the sacrificing of external validity for precision. The results appear externally valid, however, in important ways. First, the vignettes in the experiment are not based on hypothetical scenarios. Each tracks closely with the most common international events from ITERATE, a leading dataset on non-state coercion. International Terrorism: Attributes of Terrorist Events, 1968-2005 (ITERATE 5) contains detailed information from over a thousand international hostage incidents between 1968 and 2005. By far, the two most common demands issued are for governments to cede money or prisoners, which occurred in 16 percent and 11 percent of the cases, respectively. The perpetrators demand prisoners in vignette 1 and money in vignette 2 in accordance with both the relative frequency of these moderate demands and the definition of terrorism itself as an extremism of means though not necessarily ends[.[64]

Second, case studies confirm that the publics of target countries are in fact prone to inferring the extremeness of challengers’ preferences directly from their tactics, empowering anti-accommodation hardliners in the face of terrorism. Within Israel, for example, polls show that respondents who perceive the tactics of Palestinians as “mainly violent” are more likely to believe their intent is to “destroy Israel.” Conversely, respondents who perceive the tactics of Palestinians as “mainly nonviolent” are more likely to believe their intent is merely to “liberate the occupied territories.” The Russian public also infers the extremeness of Chechen preferences directly from their tactics, fortifying hardliners against terrorist appeasement. Before the terrorism commenced, Russians favoured granting an independent Chechen state. When terrorism erupted in the late 1990s, however, the Russian public concluded that the Chechens were apparently bent on harming it, shifting popular support away from concessions, while bolstering Vladimir Putin to instead bomb Grozny. Al-Qaeda’s stated grievances about U.S.-Middle East policies fell on deaf ears for the same reason. Bin Laden and his associates stressed that the purpose of the September 11, 2001 attack was to coerce the United States into withdrawing from the Middle East. But most Americans thought the point was “to harm them” as an end in itself, a perception that fuelled George W. Bush’s strong counterterrorism response in the Arab-Muslim world.[65]

Observational evidence therefore accords with the experimental results that terrorism is an inherently flawed political communication strategy. The Correspondence of Means and Ends bias can account for why terrorism impedes government compliance. Evidently, citizens of target countries do not perceive the means of terrorists as fully independent from their desired ends. Terrorists struggle to induce government compliance because they are seen as unappeasable extremists by dint of their immoderate tactical choices. When a non-state actor escalates violence directed against civilians, citizens of the target country infer that the perpetrator harbours correspondingly extreme preferences, undermining the logic of concessions regardless of whether a bargaining space objectively exists.

Academic research on terrorism offers hope that the tactic is indeed deterrable with a delegitimisation strategy. The burgeoning literature on terrorism demonstrates that the tactic hinders perpetrators from achieving—even taking seriously—their political demands. Given their incentive structure, supporters of terrorism may be deterred if only they knew what academics already do: terrorists are uniquely ill-suited for bargaining due to their grisly tactical choices, which have a proven and understandable record of political futility.



The foregoing analysis strongly suggests that most terrorism is deterrable even if many of its practitioners are not. Classical conceptions of deterrence are based on dissuading the adversary from unwanted behaviour by disincentivising it. The problem with deterring terrorists, however, is their incentive structure is so complex they are likely to derive utility from their actions regardless of the government countermeasure. Terrorism may still be deterred, however, by dissuading terrorist supporters. Supporters are essential not for terrorists to wage an isolated attack, but for them to mount a campaign of sustained operations. Terrorism has power in numbers because with greater local support, terrorists are better positioned to elude authorities and obtain material resources, necessary factors for long-term survival. In direct contrast to terrorists, their supporters are deterrable due to the simplicity of their incentive structure. People generally support terrorists for a single reason—to achieve their political demands.

Fortunately, a growing body of research finds that terrorism is a losing tactic for perpetrators to attain their demands. Four main findings attest to terrorism’s political ineffectiveness. First, terrorism is highly correlated with political failure. Historically, a surprisingly small percentage of perpetrators have managed to achieve their political platforms with terrorism. Second, the low political success rate of terrorism is inherent to the tactic itself. Coercion studies rather consistently find that nonstate actors are less likely to achieve their demands when they employ terrorism than other tactics such as guerrilla warfare, and that this correlation holds even after controlling for the capability of the perpetrators, strength of government opposition, and dozens of other potential confounds. Third, electorates do not become more dovish in the face of terrorism. On the contrary, they tend to gravitate towards more hawkish, right-wing leaders opposed to concessions. Finally, terrorism is suboptimal political behaviour because it is an inherently flawed communication strategy. Terrorism obfuscates rather than amplifies the demands of the perpetrators. Notwithstanding their actual nature, terrorists are suspected of harboring extreme political preferences by dint of their extreme tactics. This perception that terrorists are wedded to radical political views understandably dissuades target countries from trying to appease them.

Policy-makers frequently complain about the irrelevance of contemporary political science research. According to this widespread view, political scientists favour esoteric topics over intrinsically important ones and methodological rigour over clarity.[66] Such allegations may ring true for other areas of the field, but not for counterterrorism. Since the September 11, 2001 attacks, academic research has answered numerous questions about terrorism, including its political effects. Initially, many political scientists assumed that groups turn to terrorism because of its effectiveness in achieving their demands. This viewpoint has undergone a sea change, however, once subjected to empirical scrutiny. A consensus is forming that terrorism tends to steel target countries from making concessions. The policy community can help to mitigate the terrorism threat by broadcasting this message to its supporters in a targeted public diplomacy campaign. Supporters of terrorism will be deterred once they know that their actions obstruct their preferences.

About the Author: Max Abrahms is a professor of public policy in the department of political science at Northeastern University. He is also a term member at the Council on Foreign Relations. He has published extensively on the outcome of terrorism, its motives, and the implications for counterterrorism strategy. Dr. Abrahms can be reached at


[1] Glenn H. Snyder, Deterrence and Defense: Toward a Theory of National Security (Princeton: University Press, 1961).

[2] Jeffrey W. Knopft, “Use with Caution: The Value and Limits of Deterrence,” World Politics Review, June 2013. On deterring terrorism through delegitimisation, see also Alex Wilner, “Deterring the Undeterrable: Coercion, Denial, and Delegitimization in Counterterrorism,” Journal of Strategic Studies 34:1 (2011).

[3] Kroenig, Matthew, and Barry Pavel. "How to Deter Terrorism." The Washington Quarterly 35.2 (2012): 23.

[4] Andrew H Kydd and Barbara F. Walter, “The Strategies of Terrorism," International Security 31, no. 1 (2006): 49-80.

[5] Max Abrahms, “Al Qaeda's Scorecard: A Progress Report on Al Qaeda's Objectives,” Studies in Conflict and Terrorism 29.5 (2006): 509-529. A sample of primary sources includes: “Interview with Osama bin Laden,” CNN, interview broadcast 10 May 1997, posted by on 10 May 1997, at, accessed 7 August 2005; Ayman al-Zawahiri, Knights Under the Prophet’s Banner – Meditations on the Jihadist Movement (London: Al-Sharq al-Awsat, 2001) quoted in Oxford Analytica, 14 May 2002, at Oxford Analytica, “Middle East/Afghanistan: Al Qaeda Threat,”14 May 2002, at, accessed on 4 May 2005.  For an almost identical statement, see “Al-Qaeda Urges More Attacks, Al-Zawahiri Tape,” Agence France Presse, 21 May 2003, posted by at, accessed 7 July 2005.

[6] Philip Wilan and Nick Hopkins, “Bin Laden Letters Order U.S. Massacre,” The Guardian, posted 18 October 2001, at,1361,576197,00, accessed 23 August 2005.

[7] FBIS Report - GMP2005060637100, May 21, 2005.

[8] Osama bin Laden, Transcript: Translation of Bin Laden's Videotaped Message, November 1, 2004,

[9] Quoted in Alan Cowell, “Attack U.S., Qaeda Chief Tells Muslims in a Speech,” New York Times, September 13, 2013,

[10] Cullison, Alan. "Inside Al-Qaeda’s hard drive." The Atlantic Monthly 294 (2004): 55-65.

[11] Abrahms, Max, and Karolina Lula. "Why Terrorists Overestimate the Odds of Victory." Perspectives on Terrorism 6, 4-5 (2012).

[12] U.S. Department of State, “Compilation of Usama Bin Ladin Statements: 1994—January 2004,” Foreign Broadcast Information Service (Washington, DC: FBIS, 2004), at

[13] See, for example, David Rapoport, “Terrorism” in M. Hawkesworth and M. Kogan, (Eds.), Routledge Encyclopedia of Government and Politics (London: Routledge, 1992); Brian Jenkins, International Terrorism: A New Model of Conflict (Los Angeles: Crescent, 1975); Lake, David A. "Rational Extremism: Understanding Terrorism in the Twenty-first Century." Dialogue IO 1.01 (2002): 15-29; Robert Pape, Dying to win: The strategic logic of suicide terrorism. New York: Random House Digital, Inc., 2005.

[14] See, for example, Stedman, Stephen John. "Spoiler problems in peace processes." International security 22.2 (1997): 5-53; and Kydd, Andrew, and Barbara F. Walter. "Sabotaging the peace: The politics of extremist violence." International Organization 56.2 (2002): 263-296.

[15] Abrahms, Max. "What terrorists really want: Terrorist motives and counterterrorism strategy." International Security 32.4 (2008): 78-105.

[16] Quoted in The 9/11 Commission Report: Final Report of the National Commission on Terrorist Attacks Upon the United States, the National Commission on Terrorist Attacks Upon the United States (London: W.W. Norton and Company, Inc., 2004), 341.

[17] Quoted in The 9/11 Commission Report, 2.

[18] Ashton Carter, John Deutch, and Philip Zelikow, “Catastrophic Terrorism,” Foreign Affairs, Vol. 77, No. 6 (November/December 1998), 80-94.

[19] See the 9/11 Commission Report.

[20] Jessica Stern has noted, for example, that for many terrorists participating in the organisation is akin to a fun “outward bound experience”, regardless of whatever they manage to accomplish once in it. See Jessica Stern, Terror in the Name of God: Why Religious Militants Kill (New York: Ecco, 2003), 5.

[21] Stephen Flynn, “A National Security Perspective on Resilience,” Resilience: Interdisciplinary Perspectives on Science and Humanitarianism, Vol. 2, March 2011, p. 1; Stephen Flynn, “Resiliency in the Face of Unrestricted Warfare Attacks,” in Unrestricted Warfare Symposium, Johns Hopkins University, March 24-25, 2009, pp. 123-124,

[22] Max Abrahms, "Why Democracies Make Superior Counterterrorists,” Security Studies 16.2 (2007): 223-253; and Walter Enders and Todd Sandler, “What Do We Know about the Substitution Effect in Transnational Terrorism,” Researching Terrorism: Trends, Achievements, Failures 119 (2004): 137.

[23] Trager, Robert F., and Dessislava P. Zagorcheva. "Deterring terrorism: It can be done." (2006), p. 87.

[24] DeNardo, James. Power in numbers: The political strategy of protest and rebellion. Princeton: University Press, 1985.

[25] On the importance of terrorist support, see Mia Bloom, Dying to kill: The Allure of Suicide Terror (New York: Columbia University Press, 2005); and Krueger, Alan B., and Jitka Malečková. "Attitudes and action: Public opinion and the occurrence of international terrorism." Science 325.5947 (2009): 1534-1536.

[26] See, for example, Bernard Gwertzman, “Shikaki: Palestinian Mood is Pro-Peace and Anti-Terror,” Council on Foreign Relations, May 14, 2005,; Golnaz Esfandiari, “World: Poll Finds Muslim Approval Of Terrorism Declines,” RFE/RL, July 15, 2005, Shikaki, Khalil. "Palestinians divided." Foreign Affairs (2002): 89-105.

[27] See, inter alia, A.K. Cronin, ‘Behind the curve: globalization and international terrorism’, International Security  27 (3),2003 30 -58; Boaz Ganor  Defining Terrorism: Is One Man’s Terrorist another Man’s Freedom Fighter? Police Practice and Research, Vol. 3, Issue 4, 2002, pp. 287 - 3042002; Bruce Hoffman, Inside Terrorism New York: Columbia University Press, 2006; Louise Richardson What Terrorists Want.  London: John Murray, 20062006;  Nicholas Sambanis,“Terrorism and Civil War.” Terrorism, Economic Development, and Political Openness, in: Philip Keefer and Norman Loayza (Eds.) Terrorism, Economic Development and Political Openness.  Cambridge: University Press, Walzer 2002 and A.P. Schmid & A.J. Jongman. Political Terrorism. A New Guide to Actors, Authors, Concepts, Data Bases, Theories & Literature. New Brunswick, N.J.: Transaction Books, 2005.

[28] Laqueur, Walter. "The futility of terrorism." Harper's 252.1510 (1976): 99-105.

[29] Cordes, Bonnie, et al. Trends in international terrorism, 1982 and 1983. No. RAND/R-3183-SL. RAND, Santa Monica, CA, 1984, 49.

[30] Martha Crenshaw, "Theories of Terrorism: Instrumental and Organisational Approaches" The Journal of strategic studies 10.4 (1987): 15.

[31] Thomas C. Schelling, “What Purposes Can ‘International Terrorism’ Serve?” in R.G. Frey and

Christopher W. Morris, (Eds.), Violence, Terrorism, and Justice (Cambridge: University Press, 1991), p. 20.

[32] Chai, Sun-Ki. "An Organisational Economics Theory of Antigovernment Violence." Comparative Politics (1993): 99.

[33] Virginia Held, “Terrorism, Rights, and Political Goals,” in R.G. Frey and Christopher W. Morris, (Eds.), Violence, Terrorism, and Justice (Cambridge: University Press, 1991), p. 70.

[34] Abrahms, Max. "Why terrorism does not work." International Security 31.2 (2006): 42-78.

[35] Jones, Seth G., and Martin C. Libicki. How Terrorist Groups End: Lessons for Countering al Qa’ida. Rand Corporation, 2008.

[36] Cronin, Audrey Kurth. How Terrorism Ends: Understanding the Decline and Demise of Terrorist Campaigns. Princeton: University Press, 2009.

[37] Abrahms, Max. "Dying for Nothing? The Political Ineffectiveness of Suicide Terrorism." Debating Terrorism Counterterrorism (2010).

[38] Abrahms ,2006, 43-44.

[39] Jones and Libicki 2008, 32-33.

[40] Cronin 2009, 203.

[41] Abrahms, Max. "Are Terrorists Really Rational? The Palestinian Example." Orbis 48,3 (2004): 533-549; Abrahms, Max. "Al Qaeda's Scorecard: A Progress Report on Al Qaeda's Objectives." Studies in Conflict & Terrorism 29.5 (2006): 509-529; Rose, William, Rysia Murphy, and Max Abrahms. "Does Terrorism Ever Work? The 2004 Madrid Train Bombings." International Security 32.1 (2007): 185-192; Chenoweth, Erica, Nicholas Miller, Elizabeth McClellan, Hillel Frisch, Paul Staniland, and Max Abrahms. "What makes terrorists tick." International Security 33, no. 4 (2009): 180-202; Abrahms, Max. "Al Qaeda's Miscommunication War: The Terrorism Paradox." Terrorism and Political Violence 17.4 (2005): 529-549; Cronin 2009; Dannenbaum, Tom. "Bombs, Ballots, and Coercion: The Madrid Bombings, Electoral Politics, and Terrorist Strategy." Security Studies 20.3 (2011): 303-349; Moghadam, Assaf. "Suicide Terrorism, Occupation, and the Globalization of Martyrdom: A Critique of Dying to Win." Studies in Conflict & Terrorism 29.8 (2006): 707-729; Neumann, Peter R., and Michael Lawrence Rowan Smith. The Strategy of Terrorism: How It Works, and Why It Fails. New York: Routledge, 2007.

[42] Abrahms, Max. "The Political Effectiveness of Terrorism Revisited." Comparative Political Studies 45.3 (2012): 366-393.

[43] Fortna, Virginia. "Do Terrorists Win? Rebels' Use of Terrorism and Civil War Outcomes." Rebels' Use of Terrorism and Civil War Outcomes. Working Paper, Columbia University, 2011.

[44] Getmansky, Anna, and Tolga Sinmazdemir. "Success Breeds Failure: The Effect of Terrorist Attacks on Land Control in the Israeli-Palestinian Conflict." APSA 2012, Annual Meeting Paper. 2012.

[45] Stephan, Maria J., and Erica Chenoweth. "Why Civil Resistance Works: The Strategic Logic of Nonviolent Conflict." International Security 33.1 (2008): 7-44.

[46] Max Abrahms and Matthew Gottfried. “Does Terrorism Pay? An Empirical Analysis.” Forthcoming.

[47] This research finding is common, but not uncontested. A few discrepant studies suggest that under certain conditions terrorism may help militant groups to achieve their demands. See Gould, Eric D., and Esteban F. Klor. "Does terrorism work?." The Quarterly Journal of Economics 125.4 (2010): 1459-1510; Kathman, Jacob D., and Reed M. Wood. "Stopping the Killing During the “Peace”: Peacekeeping and the Severity of Postconflict Civilian Victimization." Foreign Policy Analysis (2014); Krause, Peter. "The Political Effectiveness of Non-State Violence: A Two-Level Framework to Transform a Deceptive Debate." Security Studies 22.2 (2013): 259-294; Krause, Peter. "The Structure of Success: How the Internal Distribution of Power Drives Armed Group Behaviour and National Movement Effectiveness." (2014); Thomas, Jakana. "Rewarding Bad Behaviour: How Governments Respond to Terrorism in Civil War." American Journal of Political Science (2014).

[48]Berrebi, Claude, and Esteban F. Klor. "On Terrorism and Electoral Outcomes Theory and Evidence from the Israeli-Palestinian Conflict." Journal of Conflict Resolution 50.6 (2006): 899-925.

[49] Berrebi, Claude, and Esteban F. Klor. Are Voters Sensitive to Terrorism? Direct Evidence from the Israeli Electorate. St. Monica: Rand Corporation, 2008.

[50] Gould, Eric D., and Esteban F. Klor. "Does Terrorism Work?" The Quarterly Journal of Economics 125.4 (2010): 1459-1510.

[51] Getmansky, Anna, and Thomas Zeitzoff. "Terrorism and Voting: The Effect of Exposure to Rockets on Voting in Israeli Elections."

[52] Chowanietz, Christophe. "Rallying Around the Flag or Railing against the Government? Political Parties’ Reactions to Terrorist Acts." Party Politics 17.5 (2011): 673-698.

[53] See Mueller 2006, 184, 587; Shapiro 2012, 5; and Wilkinson 1986, 52.

[54] RAND, 2009, 189.

[55] Cronin , 2009.

[56] Lapan, Harvey E., and Todd Sandler. "Terrorism and Signalling." European Journal of Political Economy 9.3 (1993): 383-397; Pape, Robert A. “The Strategic Logic of Suicide Terrorism.” American Political Science Review 97.3 (2003): 343-361.

[57] Kelly, M. J., & Mitchell, H. T. 1984. Transnational Terrorism and the Western Elite, 287.

[58] Schmid, Alex P., and Janny De Graaf. Violence as Communication: Insurgent Terrorism and the Western News Media. London: Sage, 1982, 111.

[59] Cordes, Bonnie, Paul Wilkinson, and Alasdair M. Stewart. "Euroterrorists Talk about Themselves: A Look at the Literature." Contemporary Research on Terrorism (1987): 321.

[60] Kelly and Mitchell, 1984, 287.

[61] Max Abrahms, “The Credibility Paradox: Violence as a Double-Edged Sword in International Politics,” International Studies Quarterly (December 2013).

[62] Respondents selected 1 if they believed the motive was based entirely on hatred towards Americans; 7 if they believed the motive was based entirely to achieve the moderate demand; and 4 if they believed both motives applied equally. The unlabeled values between these options allowed a more nuanced response.  A response of “uncertain” was also an option for all subjects.

[63] Subjects exposed to the painful treatment were also 13 percent less likely to rate the group’s preferences as the least extreme (p<.001). The middling option was selected the fewest times, indicating that the rubric of preferences adequately captured respondent perceptions.

[64] Oberschall, Anthony. “Explaining Terrorism: The Contribution of Collective Action Theory." Sociological Theory 22.1 (2004): 26.

[65] Abrahms, ,2006.

[66] Avey, Paul C., and Michael C. Desch. "What Do Policymakers Want From Us? Results of a Survey of Current and Former Senior National Security Decision-makers." International Studies Quarterly 58.4 (2014).



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