Economic sanctions and the dynamics of terrorist campaigns

Abstract

Although states rarely use economic sanctions specifically to combat transnational terrorism, potential targets of sanctions often face terrorist campaigns within their territory. States may avoid using sanctions against states with terrorists for fear of weakening target states excessively, thereby indirectly strengthening terrorist groups. However, this argument has not been subjected to rigorous empirical testing. This study presents a theoretical and empirical examination that explores how the imposition of sanctions affects the dynamics of ongoing terrorist campaigns in the targeted state. We argue that comprehensive sanctions that are imposed on targets that are fighting transnational terrorists within their territory should make these groups more resistant to collapse. However, similar sanctions imposed against states that serve as “home bases” or sanctuaries to terrorists should shorten the lifespan of these groups. Our empirical analysis yields results largely supportive of these theoretical expectations.

Keywords

Economic sanctions transnational terrorism

Sanctions are commonly used for reasons unrelated to transnational terrorism; yet decisions on sanction imposition can be intertwined with efforts to fight terrorism. Consider the contradiction between the sanction policy and counterterrorism objectives in the situation the US faced over the International Criminal Court (ICC). In July 2002, over 100 states participated in the founding of the ICC. The goal of the court was to provide an international tribunal to prosecute individuals that committed crimes against humanity, genocide or other crimes during war. Although agreeing in principle with the creation of the tribunal, the US refused to ratify the treaty, arguing that American soldiers might be accused of war crimes and become subject to arrest. In protest, Congress also passed the American Servicemembers’ Protection Act, which threatened to suspend military aid to any country that was party to the ICC. Numerous states responded by signing agreements barring them from turning over US soldiers to the ICC. Yet several other states faced punitive sanctions, including many key US allies that were fighting alongside American forces in the war on terror. The US therefore faced a suboptimal outcome: the threat of sanctions was instrumental to preventing states from cooperating with the ICC, but sanction imposition could undermine these states’ efforts to combat transnational terrorists.

Several studies suggest that punitive actions, such as sanctions in the aforementioned example, can harm the ability of states to engage in counterterrorism by weakening the state’s internal capacity (Carter, 2015; Piazza, 2008; Schultz, 2010). However, we presently do not have any indication to what extent sanctions harm the ability of target states to fight transnational terrorists.¹ We further have no indication of how particular types of sanctions influence the ability of transnational groups to persist and accomplish their objectives. This raises an important theoretical and policy issue: states may refuse to impose sanctions to avoid prolonging transnational terrorist campaigns, but we presently do not know if sanctions really extend these campaigns.

This study presents an investigation into how sanctions affect the survival of transnational terrorist groups. We argue that the effect of sanctions is contingent on the relationship between the terrorists and the state targeted by sanctions. Specifically, we argue that comprehensive sanctions against targets that are fighting transnational terrorists lengthen terrorist campaigns, while comprehensive sanctions used against targets that serve as “home bases” or sanctuaries accelerate the demise of terrorist groups. To develop this argument, we first present a brief literature review examining economic sanctions and the link between transnational terrorism and state capacity. We next present our theoretical framework that bridges the two bodies of literature and state testable hypotheses linking different types of economic sanctions and the duration of transnational campaigns. The following section reports results of our empirical analyses, which rely on data from the updated version of the Threat and Imposition of Sanctions (TIES) dataset and from the Jones and Libicki dataset on terrorist campaigns.² After discussing our findings, we conclude with a discussion of how sanctions may create unintended consequences in terms of combatting transnational terrorist groups.

Sanctions, terrorist groups, and unintended consequences

Much of the early conventional wisdom characterized economic sanctions as an ineffective tool used to engage in coercive bargaining. Sanctions were seen as a policy that could impose some cost on targets unless the targeted states met the demands of a particular sender. Empirical studies using the Hufbauer, Schott, and Elliott data consistently demonstrated that sanctions failed to accomplish their objectives, and often ended up doing more harm to the sender’s interests than good (Drury, 1998; Morgan and Schwebach, 1997; Pape, 1997). However, numerous theoretical and empirical studies now demonstrate that the previous findings largely resulted from selection bias (Drezner, 2003; Morgan and Miers, 1999; Smith, 1995). The general conclusion was that if targets engaged in offensive behavior, they probably already expected that sanctions would be imposed, and chose to adopt the behavior anyway despite its costs. Yet the threat of sanctions could be effective in preventing targets from adopting these offensive behaviors prior to sanction imposition. This logic and several empirical studies now indicate that sanctions, and particularly the threat of sanctions, may be a far more effective tool of coercion than previously believed (Allen, 2005; Bapat and Morgan, 2009; Early, 2011; McLean and Whang, 2010; Whang et al., 2013).

These new results demonstrating that sanctions can coerce effectively under certain conditions have led some scholars to warn that the imposition of sanctions may also produce considerable political instability within target states (McGillivray and Stam, 2004; Marinov, 2005). This pressure may be a positive result from the sender’s perspective owing to its coercive power, that is, the threat of instability might compel target states’ leaders to alter their behaviors, or acquiesce to the threat of sanctions. However, the literature on political rebellion demonstrates that increasing the political instability of a state may increase the relative power of opposition groups, including terrorist organizations (Collier and Hoeffler, 2005; Fearon and Laitin, 2003; Lake and Rothchild, 1998; Piazza, 2008). Empirically, the literature on terrorism demonstrates that these groups benefit from political instability and general economic weakness (Enders and Hoover, 2012; Justino, 2009; Weinstein, 2007). These observations suggest that terrorists within the target state stand to benefit from sanction imposition. Choi and Luo (2013) show that there is a positive relationship between sanctions and terrorism and conclude that it could be due to the increase in hardship generated by sanctions, which in turn mobilizes those who are already in the most vulnerable position to lash out against foreigners. This unintended consequence may require senders to reconsider using sanctions against target states, particularly if the terrorists appear more threatening than the target government. For example, although the US expressed concern with Yemen’s human rights record for much of the War on Terror, the US routinely refused to impose sanctions against the country, citing the need to prevent al Qaeda-affiliated terrorists or Iranian supported groups from gaining a foothold in the territory.³ Similarly, while India has numerous disputes with Pakistan, India clearly seems to prefer maintaining relations with the current Pakistani government as opposed to strengthening Kashmiri terrorist groups such as Lashkar-e-Tayyiba (LeT) or Jaish-e-Muhummad (JeM). We therefore see the critical dilemma: senders may seek to use sanctions to compel targets into altering their behavior, but fear that punishing targets could result in their destabilization. This in turn would strengthen the power of transnational terrorist groups, which are usually more hostile and threatening than target governments from the sender’s perspective.

Although this argument is accepted in policymaking circles, let us consider just how damaging sanctions are to target states’ counterterrorism efforts. At the baseline, we know that most terrorist groups do not survive for extended periods and fail to accomplish their objectives. Rapoport (1992) reported that nearly 90% of terrorist organizations do not reach their first anniversary. Several other empirical studies also demonstrate that the majority of groups do not survive for longer than 10 years.⁴ Others have noted that Rapoport’s numbers are overly pessimistic (Vittori, 2009),⁵ but the fact still remains that most groups fail early on, while only a handful groups such as FARC (Fuerzas Armadas Revolucionarias de Colombia) and ETA (Euskadi Ta Askatasuna) last for generations. Additionally, recent microlevel studies suggest that terrorist groups often suffer from considerable internal dysfunction, thereby lessening the threat they pose to state security (Forest et al., 2006; Shapiro, 2013).

The findings that terrorists are unlikely to survive and accomplish their objectives raise the question: are sanctions really all that damaging? In other words, is it the case that imposing sanctions will enable these very weak organizations to accomplish their objectives? If the conclusion is that targets are unlikely to suffer any noticeable destabilization, and terrorists are unlikely to strengthen to a significant extent, there is no justification to avoid imposing sanctions on target states that face transnational terrorists in their territory. Moreover, one could argue that sanctions may well be necessary to alter target policies that exacerbate the problem of terrorism. This raises two additional questions. First, under what conditions can senders impose sanctions against targets with terrorists in their territory? Second, are there specific types of sanctions that may be “safer” than others and less likely to produce the unintended consequence of strengthening terrorists?

Sanctions and the survival of transnational terrorists

Consider two states, a sender and a target, along with a terrorist group that is engaging in anti-government violence within the target’s territory.⁶ The sender and the target engage in some forms of economic exchanges, which may include trade, investment, and possibly transfers of foreign aid. These economic gains provide the target government with the resources it needs to provide public goods and pay its military and police forces. These resources therefore support the target’s ability to engage in counterterrorism and keep the terrorist group at bay. Let us assume that the resources available to the target government are maximized if it maintains free economic exchanges with the sender. However, if the sender chooses to threaten or impose sanctions against the target for political reasons, the sanctions introduce market imperfections that create barriers to commerce between individuals and companies within the sender and the target (e.g. McLean and Whang, 2010; Morgan and Schwebach, 1997). For example, if a sender passes a law that fines individuals US$1000 per hour if they visit a target country, this may dissuade the sender’s citizens from touring the target or entering into contracts with the target’s firm. Other sanctions, such as cuts in foreign aid or the imposition of blockades, impose costs more directly using the government’s resources.

Theoretically, increasing the cost of economic transactions indirectly or reducing inflows of capital directly may weaken the target’s economy, thereby decreasing the resources available for counterterrorism. The amount of weakening is largely a function of the type of sanction (blockades are likely more costly than asset freezes) and a sender’s level of enforcement. By reducing the gains from free commerce between itself and the target, the sender reduces the resource pool available to the target. This loss in resources may force targets to make politically difficult tradeoffs. For example, with fewer resources, a target state might have to choose between repairing roads and continuing to fight terrorists in its territory. Given that maintaining working roads is essential both for sustaining the target’s economy, and for maintaining political support, the target may devote less effort to counterterrorism in response to sanctions. This suggests that if a terrorist group is active and engaged in a campaign against the target state, the loss of economic resources may create the unintended consequence of harming the target’s counterterrorism capabilities. Since sanctions reduce the revenue available, the target state may be forced to cut back on counterterrorism operations in order to fund other activities, such as providing public goods or rewarding political allies. In cases where sanctions significantly harm the target’s economy, and create substantial reductions in government revenue, the target may weaken considerably and face much greater difficulties in suppressing terrorists within its territory.

Fortunately for the target, these effects are likely to be minimal if it is facing a purely domestic terrorist organization. Like the target, domestic terrorists draw their support strictly from within the target’s economy. Therefore, if the target’s economy is harmed by sanctions, the economic losses would affect both the government and the domestic terrorist group, thereby rendering the effects of sanctions indeterminate. However, if the government is facing transnational terrorists, the terrorists will draw support from a foreign state or population, neither of which are affected by the sender’s sanctions. As a result, while the target may suffer following the imposition of sanctions, transnational terrorists remain inoculated from these costs. The economic damage from the sender’s sanctions may therefore weaken the target government relative to the transnational terrorists. These effects will probably be more pronounced if sanctions are particularly damaging or long lasting. Theoretically, this suggests that if a state that is fighting a transnational terrorist group faces sanctions, it will be less able to suppress the group, and the terrorist campaign is likely to last longer. This logic suggests that the imposition of sanctions, although often done for reasons having little to do with transnational terrorism, may create a counterproductive effect that is similar to other large-scale policies aimed at fighting terror. Intentionally or not, governments that impose sanctions may galvanize these movements by weakening their government adversaries.⁷

To illustrate this dynamic, consider the case of the sanctions imposed by the US during the Carter Administration on Nicaragua. In the early 1970s, the Nicaraguan government headed by General Anastasio Somoza faced a nascent terrorist campaign led by the burgeoning Frente Sandinista de Liberación Nacional (FSLN).⁸ This group began conducting terrorist activities against the regime to protest corruption and Somoza’s politically motivated distribution of relief monies from the Managua earthquake of 1972. Somoza’s government quickly employed widespread torture in its effort to suppress the group. Although prior US administrations ignored these abuses owing to Somoza’s anti-communist stance, President Carter pledged during his campaign to cease American support for states that engaged in serial human rights abuses. Carter quickly fulfilled this campaign promise by suspending military aid to Nicaragua in June of 1977. A month later, Carter announced export restrictions on police equipment to Nicaragua. Costs of these sanctions amounted to approximately 1% of Nicaragua’s total GNP.⁹ Both actions were specifically aimed at weakening the capacity of Somoza to abuse his population through his campaign against the FSLN. However, Carter’s sanctions galvanized opposition to the Somoza regime, particularly given that Somoza’s repressive apparatus was losing support from the US, while the Sandinistas continued receiving support from Cuba, the Soviet Union, and from sanctuaries within Costa Rica (Hufbauer et al., 1985: 571; Schoultz, 1981: 363). This analysis suggests that the export restriction on police and military equipment to Nicaragua undermined Somoza’s efforts to suppress the FSLN, assisted the group in transitioning from a terrorist organization to a full blown guerrilla insurgency, and ultimately facilitated the collapse of the Somoza regime. In this case, Carter’s sanctions against Nicaragua clearly undermined a key US goal of containing Communist subversives in the country. These sanctions were seen as so counterproductive that the Reagan Administration quickly reversed them upon assuming office in 1981. In announcing the suspension of Carter’s human rights sanctions, new Secretary of State Alexander Haig clearly stated, “International terrorism will take the place of human rights in our concern because it is the ultimate abuse of human rights”.¹⁰

We can identify several variables that make this general prediction more specific. First, we would not expect weaker sanctions, such as travel bans, to affect the survival of terrorist groups. Instead, we argue that more comprehensive measures, such as embargoes and blockades, are more likely to exhibit some effect on the duration of transnational terrorist campaigns. Second, target states’ counterterrorism efforts are likely to become enhanced by resources gained from senders’ exports. However, if states in the international system restrict their exports to targets, this undermines the ability of these states to augment their fight, and may undermine its effectiveness.

Hypothesis 1. Comprehensive sanctions (embargoes and blockades) against states that are fighting transnational terrorists make the collapse of these groups less likely.

Hypothesis 2. High-cost sanctions against states that are fighting transnational terrorists make the collapse of these groups less likely.

Hypothesis 3. Export restrictions against states that are fighting transnational terrorists make the collapse of these groups less likely.

The logic of Hypotheses 1–3 is that comprehensive and costly sanctions that undermine exports to the target state undermine effective counterterrorism by weakening the target’s capacity. In these cases, the target of sanctions is also the target of the terrorist group, and is the location where the group conducts its terrorist attacks. Let us now assume that rather than sanctions being directed at the terrorists’ attack location, sanctions are instead directed at a target that serves as the terrorists’ home base. A home base is the location from where terrorist groups stage attacks. For example, both the LeT and JeM stage attacks against Indian-held Kashmir from their bases in Pakistan. In this case, Pakistan serves as the home base for these two groups, whereas India serves as their attack location.

There are two types of relationships transnational terrorists may have with the governments of their home bases. One possibility is that the government of the home base has a cooperative relationship with the terrorists and shares the group’s foreign policy goals. In this case, the target may allow the group to use its territory to stage attacks against its rivals, or may provide the group with direct support or sponsorship. These activities tend to make terrorist organizations more violent and more resistant to collapse (Bapat, 2012; Byman, 2005; Carter, 2012; Salehyan, 2009; Weinstein, 2007). The relationship between Pakistan and both the LeT and JeM captures this relationship. The Pakistani government directly supports the efforts of these groups to undermine Indian control over Kashmir. Both the state and the terrorists share the same goal of evicting India from the territory.

An alternative possibility is that the government of the home base is hostile to the transnational terrorists operating within its territory.¹¹ Despite this hostility, the terrorists may draw passive support from sympathetic populations within the territories of home base states (Byman, 2005; San Akca, 2015). For example, the transnational terrorist group known as Jemaah Islamiyah maintains cells in multiple Southeast Asian states. Based in Indonesia, the group has attempted to attack the interests of the US, Malaysia, the Philippines, and Singapore. Although the Indonesian government views the group as hostile, and has made efforts to crack down on it since the infamous 2002 Bali nightclub bombing, the group continues to draw support and local contributions from within Indonesian territory, as well as from charitable organizations in the Middle East. In this case, as well as others, it is often quite difficult for the government of the home base to crack down and stop the passive support given to the group from other non-state actors. For example, if transnational terrorists draw support from populations in border regions, these areas may be geographically far from the home base government or difficult to access owing to poor infrastructure. Alternatively, transnational terrorists may draw passive support from a key constituency of the home base government. Regardless, it is possible for transnational terrorists to gain resources from a home base, even in cases where the home base government is hostile to the group.

This raises the question: how would the imposition of sanctions against the home base of transnational terrorists affect their ability to continue their campaigns of violence? Although the imposition of sanctions is unlikely to stop active or passive support for transnational terrorists outright, sanctions can raise the price of both activities. In the case of active support, targets may rely on revenues generated by external trade to finance their support of terrorism. Therefore, if senders were to raise tariffs on goods from the home bases of terrorist organizations, the cost to these states of continuing to finance terrorism will increase over time. In effect, the rising cost relative to a constant gain may diminish the future value of supporting terrorism, which may encourage active supporters to abandon this activity. The pressure to stop supporting terrorism should further increase when active supporters forecast future economic downturns: if sanctions raise the price of goods, active supporters may be unable to finance multiple objectives. This may push active supporters to make choices such as providing private goods for government allies or maintaining support for terrorists. If this is the case, we would expect that over time sanctions against terrorists’ home bases will weaken these groups and accelerate their collapse. Sanctions may create similar pressures on passive support over time. The market imperfection introduced by sanctions may raise the prices of goods and services, thereby leaving fewer resources for civilians in the group’s home bases to aid terrorist operations. Individuals may therefore lose the disposable income they have to provide charitable contributions to terrorists, which in the aggregate may weaken the group’s capabilities.

The damage created by sanctions directed at the home bases of transnational terrorists may therefore create multiple conditions that undermine the group’s ability to continue its terrorist campaigns. First, the damage may make the support that these groups receive less efficient. These inefficiencies may leave the group vulnerable to collapse by weakening its capabilities and undermining its ability to sustain collective action. Second, the loss of revenue from sanctions may make the more vulnerable populations in a home base poorer, thereby making these individuals less able to provide assistance to terrorists. Third, the economic damage created by sanctions may induce the governments of target states to strike deals with sending states. Targets may offer to disarm their terrorists in exchange for sanctions relief. For example, the Abu Nidal Organization was expelled by Saddam Hussein’s Iraq in 1983, Hafez al Assad’s Syria in 1987, and Muammar Gaddafi’s Libya in 1999. In each case, the home bases took this action to gain relief from international sanctions. Although sanctions did not immediately compel these states to shut down Abu Nidal, the expulsion of the group became a valuable bargaining chip for each of these home bases. In sum, this suggests that sanctions may compel active and passive supporters into abandoning support for their transnational terrorists. We expect comprehensive sanctions to be the most effective in compelling home bases to disarm their terrorists. However, unlike terrorist targets (or attack locations), home bases are more likely to be affected by import restrictions that limit their ability to sell their goods on the world market, thereby generating revenues that can be used to support terrorist groups.

Hypothesis 4. Comprehensive sanctions (embargoes and blockades) against home bases of transnational terrorists make the collapse of these groups more likely.

Hypothesis 5. High-cost sanctions against home bases of transnational terrorists make the collapse of these groups more likely.

Hypothesis 6. Import restrictions against home bases of transnational terrorists make the collapse of these groups more likely.

Testing the hypotheses: data and method

To test the hypotheses formulated in the previous section, we create a dataset that combines information from two primary sources: the updated TIES dataset and Jones and Libicki’s (2008) data on terrorist groups. The TIES dataset provides information on the time frame of each sanction episode, as well as various characteristics of sanctions: the type of imposed sanctions, specific measures that were utilized against the sanctioned state, and the scope of sanctions. The sanction episodes included in the TIES dataset were initiated in the period from 1945 to 2005. While the total number of observations in TIES is 1412, sanctions were in fact imposed in 845 cases. We identify comprehensive sanctions as those that can significantly contribute to a weakening of the target’s capabilities. These include embargoes (partial or total) and blockades. We also create an alternative measure for comprehensive sanctions, which gauges whether the target experienced major or severe sanction costs. In addition, we create measures to capture import and export restrictions. We drop episodes of threatened sanctions that were never imposed owing to either the target’s decision to concede or the sender’s reluctance to follow through on its threat, because our theoretical argument suggests that sanctions affect the survival of terrorist groups through costs generated by the implementation of sanctions. The Jones and Libicki dataset contains variables that identify terrorist groups and countries in which the groups operate, the years of operation, the type of each group and its main objective, and the manner in which the group ended its existence. The number of groups for which we have this information is 648, and their operation years range from 1866 to 2006. After eliminating purely domestic terrorist campaigns, we are left with a list of 209 transnational campaigns, with the operation period between 1922 and 2006, which means that our unit of analysis is group-year. A significant number of these transnational campaigns—150—ended during the period under study, but only 35 collapsed because of police or military actions taken by the government.

Note that our analysis focuses on terrorist groups that operate in more than one country at the same time. Also, not all surviving groups are active until the last year of their terrorist campaigns. Therefore, we modified the Jones and Libicki dataset using information from the Global Terrorism Database (GTD) and the Terrorist Organization Profiles (TOPs).¹² We begin by dropping all groups that are purely domestic. To do this, we first coded attack locations for each group, as well as countries that serve as home bases. If a group conducted attacks only in the country that served as its home base, such a group is a domestic group (e.g. Liberation Tigers of Tamil Eelam, and Laskar Jihad) and hence is dropped from the dataset; otherwise, it is considered a transnational group and is included in the data.¹³ Second, the year of the last attack recorded in the GTD is treated as the final year of the terrorist campaign. Third, for transnational groups with multiple attack locations and/or home bases, we needed to choose one country in each set in order to construct control variables for country-specific determinants of terrorist groups’ survival. Based on previous work indicating that transnational terrorists often base within weaker state environments (Bapat, 2007; Krieger and Meierrieks, 2011; Piazza, 2008), we assume that a group’s ability to carry out attacks is the greatest in the weakest (in terms of its capabilities) country. We identify the weakest country by comparing GDP per capita of all attack locations for each terrorist group and choose the one with the lowest value.¹⁴ We repeat the same coding procedure for home bases to choose the weakest home base, since the weakest states should be least successful in their counterterrorist efforts. This procedure also helps us eliminate most of the cases in which major powers are either attack locations or home bases of transnational groups. Major powers tend to be most successful in eliminating terrorist threats within their borders, while being targets of frequent sanctions episodes.¹⁵ For instance, the US has been sanctioned more frequently than any other country, that is, 59 times, according to the TIES dataset, which represents more than 7% of all sanction impositions.¹⁶ Subsequently, we treat the weakest country as the main country for which all country-specific variables are obtained. As a result, we have two sets of control variables: one for the weakest attack location, and the other for the weakest home base.¹⁷

The objective of this study is to evaluate factors determining the survival of transnational terrorist groups.¹⁸ Since Figure 1 suggests that terrorist campaigns that collapse tend to do so quite quickly, we test our hypotheses using the Weibull survival model. Each model clusters standard errors by country. To estimate a survival model, we rely on two variables. Group collapse is coded as 1 in the year when a group is eliminated through the use of military or police force, and 0 otherwise. We also create a count variable (Group time) that counts the number of years since the beginning of the group’s life cycle until a given year, before the group’s terrorist campaign ends.

Figure 1.

Distribution of failed terrorist groups’ duration periods from start to collapse.

Explanatory variables

To test the hypotheses that link group and government characteristics and the use of sanctions to the likelihood of terrorist groups’ collapse, we rely on two sets of variables. First, Jones and Libicki’s dataset provides information on group size (Group size), coded as an ordinal variable ranging from 0 when a terrorist group has fewer than 100 members, to 3 when a group has more than 10,000 members. Previous research suggests that a larger group size increases terrorist groups’ survival odds (Gutfraind, 2009). We also count the number of attack location and home base states for each terrorist group to create the Number of homebases/attack locations variables: it is probably more difficult to defeat groups that operate in numerous locations than groups with a more restricted scale of operations. Values of Number of attack locations range from 1 to 10—the maximum number of states corresponds to Black September, a clandestine wing of al-Fatah, which carried out a number of attacks in the Middle East, North Africa, Western Europe and North America. Values of Number of homebases range from 1 to 7: the groups with the highest number of home bases are Aum Shinrikyo and the Islamic Movement of Uzbekistan. Finally, we control for the country’s regime type and its durability: political institutions may constrain governments’ counter-terrorism efforts to a varying extent, support different degrees of freedom of association and communication, as well as allow more (or less) independent and reliable mass media (Hoffman, 2006; Li, 2005). The Regime type variable is a country’s Polity2 score, ranging from −10 (strongly autocratic regimes) to 10 (strongly democratic regimes). The Regime durability variable (logged) gauges how durable the country’s regime is: it is a count of the number of years since the last political transition. These two measures were extracted from the Polity IV dataset.

Third, to be able to test our hypotheses, we construct several variables that capture the use of sanctions and measure relevant characteristics of sanctions imposed on the country in which one or more terrorist groups operate. The source of information on sanctions is the TIES dataset. First, we create variables to capture comprehensive sanctions. We rely on the Sanction type variable of the TIES dataset to code the following two dummies: Embargo equals 1 if Sanction type equals 1 or 2 (i.e. total or partial economic embargo) and 0 otherwise; and Blockade equals 1 if Sanction type equals 5 (i.e. blockade) and 0 otherwise. We also create a dummy for sanctions that impose major or severe sanction costs on the target as an alternative measure of comprehensive sanctions (High-cost sanctions). When the Target economic costs variable of the TIES dataset takes the values of 2 or 3 (i.e. major or severe costs), the dummy takes the value of 1; otherwise, it equals 0. In addition, we create two sanction variables that represent import and export restrictions imposed by sanctioners against the target country: Import sanction equals 1 if Sanction type equals 3 (i.e. import restriction) and 0 otherwise; Export sanction equals 1 if Sanction type equals 4 (i.e. export restriction) and 0 otherwise. Note that the Sanction type variable of the TIES dataset codes all applicable sanction types for each sanction episode; therefore, the resulting sanction dummies are not mutually exclusive.

Theoretically, the most comprehensive forms of economic sanctions are embargoes and blockades, given that both essentially shut down commerce between the sender and the target. Hypothesis 1 therefore predicts that these types of sanctions are more likely to prolong terrorist campaigns when directed at targets that are fighting terrorists. Hypothesis 2 predicts that high-cost sanctions of all types, including those that do not fall into the embargo and blockade categories, are also likely to prolong the survival of transnational terrorists. The third hypothesis specifically examines how export restrictions affect the ability of target states to defeat transnational terrorist campaigns. Each of these hypotheses predicts that sanctions should prolong the survival of these groups.

Hypotheses 4–6 examine how these variables affect the survival of terrorists in their home bases/sanctuaries. These hypotheses predict that the independent variables should have the opposite effect on campaign duration. That is, while sanctions against targets that are fighting terrorists prolong these campaigns, sanctions against home bases shorten campaigns and encourage the demise of terrorist groups. Hypothesis 4 predicts that embargoes and blockades should accelerate the demise of terrorist groups when directed at their home bases, whereas Hypothesis 5 indicates that costlier sanctions should also shorten campaigns when directed at home bases. Hypothesis 6 indicates that import sanctions harm home bases. Therefore, terrorist group survival should become more likely when export restrictions are imposed against countries attacked by terrorists, whereas terrorist groups should be more likely to collapse when sanctioners use import restrictions against terrorists’ home base countries.

Finally, we utilize a number of control variables identified in previous studies as important determinants of terrorist campaign duration. The impact of economic sanctions on a state can be exacerbated or weakened by the presence of other factors influencing its vulnerability to economic sanctions. We include several such variables to capture relevant economic and geographical aspects of target states.

We create a measure of a state’s trade dependency by calculating the percentage of trade over total GDP (Trade dependence). The higher the percentage of trade as a share of GDP, the more dependent the host state is on economic interactions with other states. Sanctions imposed against such states should be more economically damaging to the government and, thus, should positively affect the duration of terrorist campaigns. Furthermore, Blomberg et al. (2011) suggest that trade openness should be positively associated with terrorist groups’ survival if trade flows provide opportunities for terrorists to import necessary supplies.

In addition to international economic linkages, the civil conflict literature has identified numerous factors influencing states’ propensity to experience political violence. Many previous studies have linked larger populations to a higher risk of conflict (Fearon and Laitin, 2003; Hegre and Sambanis, 2006). Scarcity theories suggest that more populous states have more competition for scarce resources. Similarly, lower levels of GDP per capita and GDP growth are often linked with instability and increase in support for terrorist groups. Lower GDP per capita and GDP growth indicate lower levels of economic opportunities and greater poverty, and hence more significant motivations for violence. The source of data for these variables (Trade dependence, Population, GDP per capita and GDP growth) is the World Bank’s World Development Indicators, and we use a logarithmic transformation of the trade ratio, GDP per capita and population variables in our analyses.¹⁹

Geographical factors can also be linked to terrorist groups‘ strength, as well as the government’s ability to defeat them. Non-contiguous and mountainous territories tend to serve as safe shelters for terrorist groups and are more difficult for governments to subdue and control. We use two measures from Fearon and Laitin’s (2003) study of states’ vulnerability to militant challenges: the logged share of the country’s territory that is mountainous (Nested mountains), and a dummy variable (Non-contiguous) that takes the value of 1 if the country has a non-contiguous territory and 0 otherwise.

Finally, to control for the effect of the Cold War rivalry between the US and the USSR on terrorist group survival, we code a dummy variable. Cold War takes the value of 1 for the years between 1947 and 1991, and 0 otherwise.

For robustness checks reported in the Appendix, we created additional control variables. First, to capture group characteristics, we use Jones and Libicki’s classification of terrorist groups by type: religious, nationalist, left- or right-wing. For each characteristic, we create a dummy variable that takes the value of 1 when this characteristic is present, and 0 otherwise. Second, we code two dummy variables for the issue type involved in a particular sanction episode: these variables allow us to distinguish sanctions motivated by political considerations and sanctions driven by economic disagreements. The Political issue dummy equals 1 if the Issue variable of the TIES dataset takes the values of 1–11 (contain political influence, contain military behavior, destabilize regime, release citizens, property or material, solve territorial dispute, deny strategic materials, retaliate for alliance or alignment choice, improve human rights, end weapons/material proliferation, terminate support of non-state actors and deter or punish drug trafficking practices), and 0 otherwise. The Economic issue dummy equals 1 if the Issue variable of the TIES dataset takes the values of 12–14 (improve environmental policies, trade practices, implement economic reform), and 0 otherwise. Third, we create a dummy variable that indicates whether or not the terrorist group controls some territory (Territorial control).

Discussion of empirical results

Table 1 presents the results related to sanctions against targets that are fighting terrorists. The results provide empirical support for Hypotheses 1–3. Each model demonstrates that sanctions are associated with an increase in the amount of time it takes for governments targeted by terrorist groups to terminate terrorist campaigns. The coefficients on the Blockade and High-cost sanction variables indicate that transnational terrorist campaigns face a lower hazard of ending when these groups fight against countries that are targets of comprehensive sanctions. The coefficient on another variable that represents comprehensive sanctions (i.e. Embargo) fails to reach statistical significance at conventional levels. This supports the argument that the counterterrorism efforts of target states are adversely affected by sanctions that weaken targets’ economies and force these countries to spend less on counterterrorism programs. Regression results reported in the last column of Table 1 provide support for Hypothesis 3, which states that when senders restrict exports to countries fighting transnational terrorist groups, targets’ capabilities to combat terrorists are weakened as targets lose access to goods produced by senders’ companies. Taken together, these findings indicate that comprehensive sanctions such as blockades, along with export sanctions, may harm the ability of targets to suppress their transnational terrorists.

Table 1.

Determinants of terrorist groups’ forced end (attack location controls)

	M1	M2	M3	M4
	Embargo	Blockade	High-cost sanction	Export sanction
Sanctions I.V.	−0.42	−14.35**	−14.95**	−1.77**
	(0.97)	(0.93)	(0.45)	(0.69)
Group size	−1.18**	−1.21**	−1.16**	−1.25**
	(0.57)	(0.56)	(0.53)	(0.54)
Number of attack locations	−0.14	−0.13	−0.12	−0.12
	(0.17)	(0.17)	(0.17)	(0.17)
Trade dependence	0.18	0.18	0.14	0.22
	(0.56)	(0.53)	(0.53)	(0.54)
Population	−0.12	−0.13	−0.13	−0.06
	(0.26)	(0.24)	(0.24)	(0.23)
Regime durability	0.29	0.30	0.29	0.31
	(0.20)	(0.20)	(0.20)	(0.20)
Nested mountains	0.64**	0.63**	0.63**	0.50*
	(0.29)	(0.27)	(0.27)	(0.28)
GDP per capita	0.35**	0.28	0.33*	0.35**
	(0.17)	(0.18)	(0.18)	(0.18)
GDP growth	−0.00	−0.00	0.00	−0.01
	(0.04)	(0.04)	(0.04)	(0.04)
Non-contiguous	1.65**	1.63**	1.57**	1.73**
	(0.51)	(0.48)	(0.48)	(0.52)
Regime type	−0.08**	−0.07**	−0.08**	−0.09**
	(0.03)	(0.03)	(0.03)	(0.03)
Cold War	0.04	0.10	0.04	−0.18
	(0.65)	(0.65)	(0.66)	(0.69)
Constant	−7.47	−6.70	−6.88	−8.09
	(7.66)	(7.22)	(7.21)	(7.00)
ln_p	0.11	0.10	0.09	0.14
	(0.17)	(0.16)	(0.16)	(0.15)
Observations	1372	1372	1372	1372
Log likelihood	−60.72	−59.98	−59.33	−58.80
Wald test	62.36	865.95	2130.16	69.43

p < 0.10; **p < 0.05.

Table of coefficients; robust clustered standard errors in parentheses.

We turn next to the tests of Hypotheses 4–6, reported in Table 2. We find substantial empirical support for the hypotheses in the models that capture campaign duration until the terrorist groups’ forced end. Table 2 demonstrates that sanctions against home bases of transnational terrorists can increase the probability that these groups will meet a forced end. Specifically, the imposition of an embargo or high-cost sanctions significantly increases the likelihood of group collapse. One surprising finding presented in column 2 is that blockades all but eliminate the probability of a forced end, contrary to our expectations. These findings suggest that sanctions against home base states are likely to push terrorists to their demise, but some excessive sanctions, such as blockades, may be counterproductive. Table 2 further demonstrates that import restrictions accelerate the demise of transnational terrorist groups, which is supportive of Hypothesis 6. This indicates that sanctions that prevent home bases of terrorists from selling their goods and services on the open market may be more effective in compelling these states to stop supporting their terrorists.

Table 2.

Determinants of terrorist groups’ forced end (home base controls)

	M1	M2	M3	M4
	Embargo	Blockade	High-cost sanction	Import sanction
Sanctions I.V.	1.05**	−12.54**	1.11**	1.26*
	(0.52)	(1.12)	(0.54)	(0.65)
Group size	−0.63*	−0.68*	−0.61*	−0.69*
	(0.35)	(0.37)	(0.35)	(0.39)
Number of home bases	0.09	0.07	0.08	0.13
	(0.33)	(0.36)	(0.34)	(0.37)
Trade dependence	−0.08	0.01	−0.07	−0.14
	(0.42)	(0.40)	(0.42)	(0.45)
Population	0.47	0.47	0.43	0.36
	(0.39)	(0.44)	(0.41)	(0.46)
Regime durability	−0.43*	−0.38*	−0.42*	−0.42*
	(0.22)	(0.22)	(0.23)	(0.23)
Nested mountains	0.07	0.09	0.00	0.05
	(0.37)	(0.34)	(0.37)	(0.38)
GDP per capita	0.84**	0.84**	0.86**	0.72*
	(0.36)	(0.35)	(0.36)	(0.40)
GDP growth	−0.03	−0.04	−0.02	−0.03
	(0.04)	(0.04)	(0.04)	(0.05)
Non-contiguous	0.00	−0.22	−0.10	0.06
	(0.70)	(0.75)	(0.74)	(1.02)
Regime type	−0.08*	−0.09**	−0.08*	−0.11**
	(0.05)	(0.04)	(0.05)	(0.04)
Cold War	−0.38	−0.30	−0.37	0.06
	(0.61)	(0.64)	(0.64)	(0.68)
Constant	−17.54*	−17.41	−16.59	−14.74
	(9.99)	(10.91)	(10.38)	(11.17)
ln_p	0.10	0.05	0.05	0.02
	(0.10)	(0.11)	(0.10)	(0.11)
Observations	1325	1325	1325	1325
Log likelihood	−48.95	−50.51	−49.03	−48.49
Wald test	47.29	372.04	49.09	35.88

p < 0.10; **p < 0.05.

Table of coefficients; robust clustered standard errors in parentheses.

Our control variables also yield a number of important findings. As expected, terrorist campaigns are less likely to collapse when group size increases, and when governments of home bases and attack locations are more democratic. On the other hand, GDP per capita of home bases and attack locations appears to reduce the duration of terrorist campaigns, which could be due to affluent countries’ greater effectiveness in counterterrorism as well as lower willingness to serve as a home base for a terrorist organization. Terrorist campaigns also tend to end more quickly when attack locations have mountainous or non-contiguous territories, which is contrary to our expectation that such geographical characteristics would increase group survival. None of the remaining control variables yield statistically significant results.

The results paint a nuanced picture regarding how sanctions affect terrorist campaigns. On the one hand, the analyses lend empirical support to the argument that sanctions can harm states that are fighting transnational terrorists, particularly if these sanctions are comprehensive, high cost, and involve restrictions on exports. Figure 2 shows that transnational campaigns in such states remain much more resilient over time than in states that do not experience sanctions. On the other hand, our results suggest that comprehensive and high-cost sanctions, as well as import restrictions, can force home bases to withdraw their support for transnational terrorist campaigns, thereby accelerating the demise of transnational terrorists within their territory. Figure 3 demonstrates that survival odds of groups in sanctioned home bases decline faster over time than in home bases that are not targeted by such sanctions. Taken together, these findings support two policy recommendations. First, senders that value counterterrorism should avoid imposing comprehensive sanctions against countries targeted by transnational terrorist groups. These sanctions may be counterproductive in undermining states’ ability to fight terrorists. Second, comprehensive sanctions may incentivize home base states to pull back their assistance to transnational terrorists, but excessively punitive sanctions, such as blockades, will not.

Figure 2.

Survival graphs for different sanction types (attack location controls).

Figure 3.

Survival graphs for different sanction types (home base controls).

Conclusions

We began with the observation that policymakers sometimes express their reluctance to impose sanctions against targets that are combating transnational terrorist organizations. The argument against sanctions in such situations is that sanctions damage the target’s economy, which could in turn decrease the target’s ability to fight transnational groups. Sanctions may therefore be counterproductive to the sender’s strategic interests, particularly if the target’s domestic instability represents a security threat. Although this reasoning could justify states’ refusal to impose sanctions, as in the case of overturned US sanctions against Pakistan following Osama bin Laden’s death, the argument has never been empirically tested. No previous study systematically examines the relative damage caused by sanctions to counterterrorism efforts.

This study represents an attempt to fill this void and examine when and if sanctions truly do undermine target states’ ability to engage in counterterrorism against transnational groups. Our results yield several interesting conclusions. First, we find that sanctions imposed against target states that are fighting transnational terrorists may prolong the survival of these groups. This finding suggests that sanctions are counterproductive when they impose significant economic damage on target states fighting transnational terrorists, or when sanctions restrict targets’ access to exports from sender countries. However, our empirical analyses also show that comprehensive sanctions and import restrictions directed at home bases of terrorist organizations may encourage these states to scale back their support for transnational terrorists. In sum, these results indicate that sanctions harm states that are attack locations of transnational terrorists, but that sanctions can be valuable if directed at transnational terrorists’ home bases. To illustrate, consider the effect of sanctions on the Haqqani Network’s campaign against the Afghan government. In this case, sanctions against Afghanistan are counterproductive since this state is targeted by the Haqqanis and serves as an attack location, but sanctions against Pakistan may be valuable since the group’s home base is in the area of Miram Shah, which is in the North Waziristan Agency of Pakistan.²⁰

These findings raise an interesting question: if senders are aware that imposing sanctions against attack locations is counterproductive, but imposing sanctions against home bases may be beneficial, why do senders ever impose sanctions against attack locations? Although our analysis uses several coding rules to classify attack locations and home bases, the empirical world may often present cases (such as Afghanistan and Pakistan) that are quite complex. In these cases, it may be difficult to discern if a state is only an attack location and a victim of terrorism, or if the state is a willing home base of the terrorist group. One interesting implication of this analysis is that if sanctions undermine states that are fighting terrorists, but assist in counterterrorism against states that are sheltering transnational terrorists, targets may have an incentive to misrepresent the nature of their relationship to terrorist groups. To avoid sanctions, these states may seek to mask their relationship with terrorists and claim to be attack locations, rather than home bases. In this way, we would expect plausible deniability to be essential to furthering the survival of terrorist campaigns.

Footnotes

Appendix

Table A1.

List of transnational terrorist groups included in the analysis

Abu Hafs al-Masri Brigade	East Turkistan Liberation Organization
Abu Nidal Organization	Eastern Turkistan Islamic Movement
Abu Sayyaf Group	Egyptian Islamic Jihad
Achik National Volunteer Council	Eritrean Islamic Jihad Movement
Albanian National Army	Eritrean Liberation Front
All Burma Students’ Democratic Front	Eritrean People’s Liberation Front
All Tripura Tiger Force	Ethiopian People’s Revolutionary Army
Ananda Marga	Fedayeen Khalq
Animal Liberation Front	Fighting Jewish Organization
Ansar Allah	Free Aceh Movement
Anti-Imperialist International Brigade	Free Papua Movement
Anti-Terrorist Liberation Group	Free Vietnam Revolutionary Group
Arab Communist Organization	Front for the Liberation of Lebanon from Foreigners
Arab Liberation Front	Front for the Liberation of the Cabinda Enclave
Arab Nationalist Youth for the Liberation of Palestine	Front for the Liberation of the French Somali Coast
Arabian Peninsula Freemen	Generation of Arab Fury
Argentine Anti-Communist Alliance	God’s Army
Armed Forces of National Liberation	Greek Bulgarian Armenian Front
Armenian Red Army	Group of the Martyrs Mostafa Sadeki and Ali Zadeh
Armenian Resistance Group	Guardsmen of Islam
Armenian Revolutionary Army	HPG
Armenian Secret Army for the Liberation of Armenia	Hamas
Army for the Liberation of Rwanda	Harakat ul-Ansar
Asbat al-Ansar	Harakat ul-Jihad-i-Islami
Aum Shinrikyo	Harakat ul-Mujahidin
Baader-Meinhof Group	Hector Riobe Brigade
Babbar Khalsa International	Hizb-I Islami Gulbuddin
Baloch Liberation Army	Hizballah
Battalion of the Martyr Abdullah Azzam	Hizbul Mujahideen
Black December	Independent Armed Revolutionary Movement
Black Panthers	Informal Anarchist Federation
Black September	International Justice Group
Bodo Liberation Tigers	International Revolutionary Action Group
Bolivarian Guerilla Movement	Irish National Liberation Army
Borok National Council of Tripura	Irish Republican Army
Cambodian Freedom Fighters	Islami Inqilabi Mahaz
Chadian People’s Revolutionary Movement	Islamic Action in Iraq
Che Guevara Brigade	Islamic International Peacekeeping Brigade
Chilean Committee of Support for the Peruvian Revolution	Islamic Liberation Organization
Cinchoneros Popular Liberation Movement	Islamic Movement for Change
Committee for the Security of the Highways	Islamic Movement of Uzbekistan
Committee of Solidarity with Arab and Middle East Political Prisoners	Jaish-e-Mohammad
Communist Party of Nepal-Maoist	Jamiat ul-Mujahedin
Continuity Irish Republican Army	Jammu and Kashmir Islamic Front
Democratic Front for the Liberation of Palestine	Japanese Red Army
Earth Liberation Front	Jemaah Islamiya
Jenin Martyr’s Brigade	Palestinian Revolution Forces General Command
Jund al-Sham	Pan-Turkish Organization
Justice Commandos for the Armenian Genocide	Pattani United Liberation Organization
Kach	Peace Conquerors
Kahane Chai	People’s Liberation Army
Karenni National Progressive Party	People’s Revolutionary Party
Kayin National Union	Peykar
Kumpulan Mujahidin Malaysia	Polisario Front
Kurdistan Freedom Hawks	Polish Revolutionary Home Army
Kurdistan Workers’ Party	Popular Front for the Liberation of Palestine, General Command
Lashkar-e-Jhangvi	Popular Front for the Liberation of Palestine
Lashkar-e-Taiba	Popular Movement for the Liberation of Angola
Latin American Patriotic Army	Popular Resistance Committees
Lebanese Armed Revolutionary Faction	Puerto Rican Resistance Movement
Lord’s Resistance Army	Raul Sendic International Brigade
Loyalist Volunteer Force	Real Irish Republican Army
Macedonian Revolutionary Organization	Recontra 380
Maoist Communist Center	Red Army Faction
Martyr Abu-Ali Mustafa Brigades	Revenge of the Hebrew Babies
May 15 Organization for the Liberation of Palestine	Revolutionary Organization of Socialist Muslims
Morazanist Front for the Liberation of Honduras	Revolutionary People’s Front
Moroccan Islamic Combatant Group	Revolutionary Perspective
Movement for Democracy and Development	Revolutionary United Front
Movement for Democracy and Justice in Chad	Russian National Bolshevist Party
Movement of the Islamic Action of Iraq	Russian National Unity
Movimiento Armado Nacionalista Organizacion	Salafist Group for Call and Combat
Mozambique National Reisistance Movement	Salah al-Din Battalions
Mujahedin-e-Khalq	South Maluku Republic
National Army for the Liberation of Uganda	South-West Africa People’s Organization
National Democratic Front of Bodoland	Spanish Basque Battalion
National Front for the Liberation of Angola	Spanish National Action
National Front for the Liberation of Kurdistan	Special Purpose Islamic Regiment
National Patriotic Front of Liberia	Sri Nakharo
National Socialist Council of Nagaland-Isak-Muivah	Sudan People’s Liberation Army
National Union for the Total Independence of Angola	Syrian Social Nationalist Party
National Youth Reistance Organization	Takfir wa Hijra
New Armenian Resistance	Tanzim
Ninth of June Organization	Third of October Group
Ogaden National Liberation Front	Tontons Macoutes
Omar Torrijos Commando for Latin American Dignity	Tunisian Combatant Group
Orly Organization	Uganda Democratic Christian Army
Oromo Liberation Front	Ulster Defence Association/Ulster Freedom Fighters
Palestine Liberation Front	Ulster Volunteer Force
Palestine Liberation Organization	United Nasserite Organization
Palestinian Islamic Jihad	United National Liberation Front
Palestinian Popular Struggle Front	Vigorous Burmese Student Warriors
Vitalunismo	al Madinia
West Nile Bank Front	al-Mansoorain
Workers’ Revolutionary Party	al-Quds Brigades
World United Formosans for Indepdence	al-Saiqa (Syria, Israel, West Bank/Gaza)
Yemen Islamic Jihad	al-Umar Mujahideen
Zimbabwe African Nationalist Union	al-Zulfikar
al Qa’ida	de Fes
al Qa’ida Organization in the Land of the Two Rivers	al-Ittihaad al-Islami
al Qa’ida in the Arabian Peninsula
al-Aqsa Martyrs Brigades
al-Badr (the second)
al-Bara bin Malek Brigades
al-Barq
al-Borkan Liberation Organization
al-Fatah
al-Fuqra
al-Gama’a al-Islamiyya

Authors’ note

All data, replication materials, and instructions regarding analytical materials upon which published claims rely are available online through the SAGE CMPS website.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Notes

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