Conflict and Cooperation, Middle East Crises
Ali Fisunoglu, Amir Bagherpour, Ryan Greer | Aug 2016

ISIS Foreign Fighters

An Econometric Analysis on the Global Flow of Militants Joining the Islamic State


ISIS has recruited more than 30,000 fighters from over sixty-five countries. These recruits pose a critical threat far beyond the borders of Iraq and Syria through fighters who return to their home countries to carry out terrorist attacks. It is crucial to understand why foreign fighters join ISIS in order to combat this global security risk.

giStrat performed several macro level econometric analyses on 158 countries using political, social, economic, and demographic variables in order to understand both the factors that affect the likelihood of citizens joining ISIS and the determinants for the overall number of ISIS foreign fighters from those countries.

Sociopolitical and demographic factors strongly impact an individual’s propensity to join ISIS, more so than economic factors. Specific sociopolitical and demographic factors indicating the propensity to join ISIS include:

  • Degree of ethnic and linguistic homogeneity
  • Severity of religious fractionalization
  • Existence of populist, anti-Western news reports
  • Accessibility of international networks
  • Stance of government toward Bashar al-Assad

Further analyses separated Muslim-majority countries from non-Muslim majority countries to determine whether the relative size of the Muslim population affected individuals’ propensities to join ISIS. The results indicate that Muslim-majority and non-Muslim majority countries demonstrate minor variations on the salience of certain characteristics including the stance of a government toward Bashar al-Assad.

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Variables that Affect the Flow of Foreign Fighters

Religious Fractionalization Proved More Significant than Ethno-Linguistic Fractionalization
According to our analysis, religious fractionalization and ethno-linguistic homogeneity most strongly influence both the likelihood of joining ISIS and the number of fighters joining from an individual country. We observed that religiously fractionalized countries were more likely to have citizens join ISIS, whereas countries with greater ethno-linguistic fractionalization had fewer citizens who join ISIS.

Put another way, countries which are religiously diverse are more likely to have citizens who join ISIS as foreign fighters, and the expected number of foreign fighters from these countries is higher. On the other hand, ethnic and linguistic diversity has the opposite impact. That is, countries that are ethnically and linguistically diverse are less likely to have at least one citizen join ISIS, and the expected number of foreign fighters from these countries is lower. This suggests that the process of integration becomes more challenging for the Muslim minority and catalyzes radicalization when a country is ethnically and linguistically homogenous but religiously diverse.

We observe that these variables are still significant for Muslim-majority countries, though less so than for non-Muslim majority countries.

Effects of Populist, Anti-Western Reporting       
giStrat’s analysis demonstrates that the existence of populist, anti-Western reporting—measured by the presence of foreign populist, anti-Western news bureaus that can exacerbate specific Sunni grievances—substantially increases the probability of having at least one foreign fighter join ISIS from a particular country, especially for countries where Islam is not the primary religion. However, while measurable, the effect of populist anti-Western reporting on the number of citizens who join ISIS from a given country is rather small. This result explains how ISIS can find and mobilize supporters from countries as far as Argentina, Brazil, and New Zealand, even though the number of recruits from such countries is small.

International Networks Help Produce Foreign Fighters but Do Not Determine Numbers
International networks provide financing or support for those who wish to join ISIS. Muslim-majority countries that have strong diasporas—measured by the amount of money sent home by citizens living abroad (i.e. per-capita remittances)—are more likely to supply foreign fighters to ISIS. Our findings indicate the effect of international networks on the number of foreign fighters is only significant (and positive) for Muslim-majority countries such as Jordan, Tunisia, Saudi Arabia, and Turkic states in Central Asia.

Stance of the Government Toward Bashar al-Assad Influences Number of Fighters
If a non-Muslim country’s government took an official stance against Bashar al-Assad, more people from that country can be expected to join ISIS. The government of a Muslim-majority country’s position toward Assad did not affect the likelihood of citizens joining ISIS, nor did it affect the expected number of foreign fighters.


Other Factors giStrat Measured That Were Theorized to Be Significant in Academic Literature

Distance to Syria and Iraq
Countries that are geographically closer to Syria and Iraq are assumed to have more foreign fighters because it is physically easier and less costly for them to reach ISIS strongholds. Our analysis demonstrated that this proposition is not true. The proximity of a country to Syria and Iraq does not significantly affect whether its citizens will become foreign fighters. International networks and linkages appear to be more important than geographic proximity for facilitating the flow of foreign fighters.

Democracy and Civil Liberties
It is also assumed that individuals are more likely to join ISIS when they are not able to freely participate in politics and express their opinions and beliefs. We found this is also not true. The flow of foreign fighters is not associated with the level of democracy or repression of civil liberties and political rights in a country. In short, a country’s political characteristics and freedoms are not correlated with the propensity to join ISIS.

Economic Grievances
We also investigated the potential effect of economic grievances on the tendency to join ISIS. We do not find any significant relationship between economic factors and the likelihood of joining ISIS after examining factors such as overall unemployment rate, youth unemployment rate, and economic inequality.


Major Suppliers of Foreign Fighters: Case Analysis


Tunisia is the top supplier of ISIS foreign fighters both in absolute terms (with at least 6,500 fighters) and per capita terms (with 571.4 foreign fighters per every million Tunisian citizens). Tunisia is religiously, linguistically, and ethnically homogenous, but its population is 98% Sunni; its citizens have strong ties to the Tunisian diaspora in countries like France, Italy, and Libya; and its government and media promote anti-Assad discourse—three factors that make it the largest supplier of ISIS fighters. Tunisia suffered three major terrorist attacks carried out by ISIS militants in 2015, killing 74 people and injuring 105.

Saudi Arabia
There are more than 2,500 Saudi foreign fighters, or 77.7 fighters per every million Saudi citizens, making Saudi Arabia the second largest source of ISIS foreign fighters. Saudi Arabia is a prosperous country with a predominantly Muslim population. However, due to the foreign workers living in Saudi Arabia, it is moderately diverse both ethnically and linguistically. Moreover, the government and the media promote a strong anti-Assad and anti-Western rhetoric, which fuels radical movements within the country. At least five ISIS-related terrorist attacks—mainly on Shiite targets—took place since 2014, killing at least 42 people.

There are at least 2,400 foreign fighters from Russia in ISIS, equaling 16.7 fighters per every million Russian citizens. Along with Iran, the Russian government is the biggest ally of Bashar al-Assad. Russia is a religiously diverse country: Muslims constitute approximately 11.6 percent of the Russian population, making Islam the second largest religion. A strong anti-Assad and anti-Western tone in Russian government and media, along with a history of Muslim grievances (especially in Chechnya and Dagestan), boosts the radicalization of Russian citizens and recruitment to ISIS. There is considerable ISIS activity in the North Caucasus, including at least two attacks in the Dagestan region. ISIS also claimed responsibility for downing a Russian passenger jet in Egypt, killing at least 224 people.

At least 2,100 people from Turkey joined ISIS, equaling 26.4 foreign fighters per every million Turkish citizens. Though Turkey is ethnically and linguistically diverse and religiously homogenous, its strong international networks and the widespread promotion of anti-Assad and anti-Western discourse by the government and media motivates a significant number of citizens to join ISIS. As a neighbor of Syria, Turkey has been one of the major actors in the civil war there, and it is one of the primary entry points to Syria for foreign fighters joining ISIS. Its longstanding war with the Kurdish rebels further complicates Turkey’s geo-political situation. Today Turkey is recovering from an attempted coup while fighting Bashar al-Assad, ISIS, the Kurdish opposition simultaneously. As Turkey intensified its fight against ISIS, ISIS hit back at Turkey with several terrorist and cross-border attacks, killing at least 200 people.

At least 1,700 people from France joined ISIS, equaling 26.3 foreign fighters per every million French citizens. France is a wealthy Western country with low levels of inequality and unemployment. However, an ethnically and linguistically homogenous France has had problems integrating its Muslim citizens who comprise 7.9% of the population, leading to several riots over the last ten years. Muslim citizens’ strong ties with their home countries, and the anti-Assad stance of the French government, further boosted the social alienation and radicalization of some French citizens and motivated them to join ISIS. ISIS carried out several terrorist attacks in France, killing more than 100 people.


Using a comprehensive data set and econometric models, giStrat provides a systematic analysis of the relationship between ISIS foreign fighters and various economic, social, political, and demographic factors. Our results indicate that, in contrast with popular opinion and previous peer-reviewed studies, factors related to economic equality and political freedoms are not the primary motivators for individuals who join ISIS. In fact, plenty of foreign fighters originate from economically developed countries with functioning democratic institutions. Our analysis shows that demographic and social characteristics—especially religious and political grievances—drive the flow of foreign fighters to ISIS.


giStrat applied Logit regressions to analyze the likelihood of joining ISIS, and Ordinary Least Squares (OLS) regressions to analyze the determinants of the number of foreign fighters. For the Logit regressions, the dependent variable took the value 1 if there was at least one foreign fighter from a specific country and 0 otherwise. For the OLS regressions, we took the natural log of the number of foreign fighters to normalize the data and satisfied the normality assumption of OLS. Appropriate diagnostic tests were carried out to ensure that multicollinerity was not a problem, and robust standard errors were used to eliminate the potential problem of heteroskedasticity. Autocorrelation is not an issue in this analysis as the data used is cross-sectional.


Ali Fisunoglu, PhD, Associate Analyst
Ryan Greer, Policy Advisor

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