Untitled Document

The Foreign Fighters’ Threat: What History Can (not) Tell Us

by Jeanine de Roy van Zuijdewijn


Methodological questions around the determination how many of the foreign fighters going to Syria are likely to engage in terrorism upon their return are discussed. Two approaches are used in this Research Note to assess the threat posed by Western foreign fighters in the past. These serve to answer two questions: how many of the former foreign fighters became involved in terrorist activity (approach 1) and how many of jihadist-inspired terrorists were former foreign fighters (approach 2)? The research is based on three studies (Afghanistan, Bosnia and Somalia) and the data are presented in an Appendix. A typology of foreign fighters is presented in the text itself.

Keywords: foreign fighters, Syria, Irak, jihad


The New York-based Soufan Group, an international consulting firm, estimated in June 2014 that 12,000 fighters from 81 countries have joined the civil war in Syria of which 2,500 originate from Western countries.[1] European Union Counter-terrorism Coordinator, Gilles de Kerchove, in September 2014 spoke of no less than 3,000 Europeans who have gone to Syria or Iraq to fight.[2] However, most foreign fighters come from the Middle East and North Africa.

Table 1: Foreign Fighters in Syria from selected countries (as of September 2014) [3]

This development has been unprecedented in both its scope and speed. Rallying cries to defend the ummah – the Islamic community – have been heard before, with thousands of fighters flocking to Afghanistan in the 1980s, Bosnia and Chechnya in the 1990s and Somalia, Iraq and Yemen in the last decade. Yet Syria has attracted more foreign fighters within a shorter time span.

The ongoing increase in the number of Western foreign fighters going into Syria raises security concerns. Many of these individuals are joining radical jihadist groups such as Jabhat al-Nusra and lately, the Islamic State (IS, also known by the acronyms ISIS or ISIL).[4] Authorities are worried that these fighters will returned radicalized, battle-hardened and determined to launch terrorist attacks in Western countries. Given the high number of fighters, if only a small percentage of those who return would become involved in terrorist activity, it would lead to a handful (if not dozens) of serious terrorist plots in the period ahead.

The recent change in tactics taken by IS, including the beheadings of Western journalists, shows that the organisation understands psychological warfare. These beheadings are full of symbolism (e.g. the Guantanamo Bay-like jumpsuits, Westerners publicly defying their own governments) and they reach very large audiences around the world via social media. It appears to be a text-book example of what Brian Jenkins observed in 1974: ‘Terrorists want a lot of people watching and not a lot of people dead’.[5] Jenkins revised this statement in 2006, saying that ‘[m]any of today’s terrorists want a lot of people watching and a lot of people dead’.[6] As such, IS has not shied away from mass atrocities either, as exemplified in the killing of prisoners of war.[7]

Given the current situation in Iraq and Syria, there is increased pressure on Western leaders to take forceful measures against foreign fighters. Some suggest stripping foreign fighters of their nationality, imprisoning them upon return or forbidding them to return at all.[8] Such suggestions, in turn, have invited fierce criticism. Richard Barrett, former MI6’s Counter-Terrorism chief, noting the debate about presuming British foreign fighters are guilty of involvement in terrorism unless they can prove otherwise, responded that ‘(t)his fundamental tenet of British justice should not be changed even in a minor way for this unproven threat – and it is an unproven threat at the moment’.[9] However, an attack on a Jewish museum in Brussels in May 2014 by a former foreign fighter linked to IS and the statement of David Cameron that IS-linked militants had already attempted six attacks in Europe by September 2014 serve as indicators of the gravity of this threat.[10]

The aim of this Research Note (which is based on the author’s Master’s thesis) is to provide an assessment of the threat posed by foreign fighters in previous conflicts and relate this to the current threat posed by foreign fighters in Iraq and Syria. It must be immediately acknowledged that this is only of limited value when looking at the current situation in Syria and Iraq. Context and dynamics of each conflict are distinct. Nevertheless, when trying to understand current developments, it is helpful to look at similar events in the past. The outcome of this research can certainly not be extrapolated to the current situation in Syria and Iraq but can help to identify certain parameters that are likely to influence outcomes.


Two approaches are used in this Research Note to assess the threat posed by Western foreign fighters in the past. These attempt to answer the following two questions: how many of the former foreign fighters became involved in terrorist activity (approach 1) and how many of jihadist-inspired terrorists were former foreign fighters (approach 2)?  Three case studies were conducted focusing on foreign fighters in Afghanistan, Bosnia and Somalia. In the results section, problems associated with the quantitative outcomes of such studies will be explained. Regarding the first approach, this Research Note explores the pathways of Western foreign fighters, resulting in a typology based on their post-conflict behaviour.

The second approach looks at the role of former foreign fighters in terrorist plots. It tries to complement the existing works on foreign fighters, especially the works of Thomas Hegghammer, David Malet, Petter Nesser and Aaron Zelin who have studied this issue.[11] Hegghammer’s research is most directly related to this research question as he also explored how many foreign fighters became involved in terrorist activity in the West. In this Research Note, a different definition and methodology is used to offer another perspective on the threat posed by former foreign fighters in the past.   

Before proceeding to the results, a number of elements of the research question must be defined: ‘to what extent have Western Muslim foreign fighters been directly involved in jihadist-inspired plots and attacks in Europe between 1979 and April 2013?’. The first element, Western foreign fighters, is defined in accordance to the definition used by David Malet as ‘non-citizens of conflict states who join insurgencies during civil conflicts’.[12] In the qualitative part of this study – the three historical case studies – foreign fighters from Europe, the United States and Canada are included.[13] In the second approach that investigates the presence of former foreign fighters in terrorist plots, the plots were limited to Europe. This made it possible to use the list of plots and attacks compiled by Petter Nesser.[14]

Jihadist-inspired terrorism will be defined in accordance with the definition proposed by Edwin Bakker as ‘the product of a combination of Islamist ideology and the idea of the jihad (...) in furtherance of the goals of Islam’.[15] Direct involvement in jihadist-inspired plots and attacks excludes passive support such as the financing or mere facilitation of terrorist attacks. The focus is on those who pulled the trigger or detonated the bombs -  in other words, those who posed the highest security risk.

Finally, the time span of 1979 – April 2013 needs further explanation. The year 1979 marks the Soviet invasion of Afghanistan, signalling the beginning of one of the largest and best documented mobilisations of foreign fighters in history. It was in many respects the beginning of (Western) Muslim foreign fighting we are still confronted with today. Therefore, this conflict will serve as one of the three historical case studies in part I of this Research Note. The second approach relating to the ‘foreign fighter: terrorist ratio’ covers the period 1994 – April 2013, relying on the database compiled by Nesser.

The Two Approaches: Choices and Challenges

The second approach attempts to quantify the presence of Western Muslim foreign fighters in terrorist activity in the West. This has been done carefully by Thomas Hegghammer; he concluded that 1 out of 4 terrorists was a (former) foreign fighter. His research is extremely valuable as it is one of the rare attempts to collect empirical data on foreign fighters in the past. This Research Note, however, uses a somewhat different method of measuring this threat as will be outlined below.

One of the main problems with existing research on foreign fighters is the lack of conceptual clarity: what exactly is a foreign fighter? When do we call someone a foreign fighter and when do we call him a terrorist? Foreign fighting is just one form of militant Islamist action, which can take many forms and shapes. However, Muslim foreign fighting is often described by pundits and scholars as directly related to (jihadist-inspired) terrorism. This runs the risk of overlooking some of the complexities and differences between these two concepts. This conflation of foreign fighting and jihadist-inspired terrorism has been criticised by, amongst others, Barak Mendelsohn. In his article ‘Foreign Fighters – Recent Trends’ he remarks that ‘[u]sually the discussion of the significance of the foreign fighter problem also suffers from a tendency to bracket all foreign volunteers together’.[16] He continues by saying that a foreign fighter is someone ‘fighting in a local conflict that is not his own country’s war’ while a foreign trained fighter is ‘a local who goes to another area, receives training only, and comes back to carry out attacks elsewhere, normally in his own country’.[17]

The distinction applied by Mendelsohn can be difficult to maintain, especially with regard to the ‘AfPak-region’, where (former) Al Qaeda training camps such as Khaldan, al-Farooq or Derunta transformed from sustaining the insurgency against the Soviet occupation in the 1980s to real ‘terrorist training camps’ once Al Qaeda was established. Despite these difficulties, it is useful to put ‘foreign activity’ cases into one of the two categories. Individuals who merely go to terrorist training camps but do not partake in civil conflicts are categorised as ‘foreign trainees’.

A second choice made in this Research Note that differs from previous research is the inclusion of a definition of the term ‘Western’. This Research Note tries to provide an answer to the question to what extent former Western foreign fighters are involved in terrorist activity. To answer this, it is important to distinguish Western fighters from non-Western foreign fighters. The scenario of an Algerian or Moroccan foreign fighter who eventually decides to travel to a Western country to be involved in a terrorist attack is different from that of a British, Dutch or French Muslim leaving to fight and then coming back to launch an attack.

The criteria that are used in this Research Note are as follows: a) being a citizen of a Western country by birth, b) having moved to a Western country before the age of fifteen, or c) having lived for at least ten years in a Western country prior to any terrorist activity. It must be immediately acknowledged that one can disagree with these criteria and that the empirical data for making such distinctions are uneven and often poor.[18] However, it is important to distinguish between the threat coming from ‘within’ and the so-called ‘imported’ threat. This is a first (and far from perfect) attempt to do so.

Thus, with these two modifications to existing methodologies – a distinction between fighting and training and the criteria qualifying ‘Western’ – a new database was built. This database consists of the ‘Category 1’ incidents included in Petter Nesser’s database: incidents where ‘the existence of hard evidence that a terrorist attack was planned, prepared, or launched; that an attack struck a specific target or that a target or a type of target had been identified by terrorists; and finally, that clearly identifiable jihadis were behind the planning and the attacks’.[19] The result is a new database consisting of 26 plots with 123 individuals involved.[20]  This is admittedly a small database but it is hoped that it can serve as a representative sample of all (major) jihadist plots in Europe due to the inclusion of all ‘Category 1’ incidents.

The Results

As explained in the previous section, the first approach consisted of three historical case studies because there is a significant gap in empirical data, a gap which impedes us from quantifying the overall presence of terrorists in the foreign fighter population. There is no clear picture of how many individuals became foreign fighters in the first place. William Rosenau and Sara Daly observe that probably hundreds, if not thousands of American Muslims fought in conflicts in the 1980s and 1990s but that subject has not been properly studied.[21]

This gap in knowledge is reflected in the estimates given by authors, ranging from hundreds to thousands. One scholar who tried to address this lack of understanding is investigative journalist John M. Berger. In his book Jihad Joe: Americans who go to war in the name of Islamhe estimated that at least 1,400 Americans participated in some form of jihad over the last thirty years.[22] For the European situation, it is again Hegghammer who provides some useful estimates of the size of the foreign fighter movements. Regarding the European foreign fighters in the 1990s, Hegghammer provides a conservative estimate of around two hundred individuals.[23] This estimate is based upon different reports that have completely different ranges. One report claims that several hundred Europeans fought while another one puts the number at 2,000 fighters. The total estimate of Western foreign fighters in the years 1990 to 2011 was estimated to amount to 945, according to Hegghammer a very conservative estimate. He used this number to calculate the proportion of foreign fighters involved in terrorist activity in the West. The author found 107 such cases, arriving at the conclusion that there is a ‘one-in-nine-radicalization rate that would make foreign fighter experience one of the strongest predictors of individual involvement in domestic operations that we know’.[24]

However, there are some reasons to question this. The most important one has been indicated by the author himself as he adds that this must be seen as a maximum rate.[25] This qualification is often overlooked by media, government agencies and scholars, who make this rate seem more ‘cast in stone’ than the author had probably intended.[26] As this is a conservative estimate, it is based upon continuous rounding down of the subtotals of foreign fighters. The low bar of inclusion for foreign fighters – including foreign trainees and not excluding non-Western foreign fighters – leads to a higher number of foreign fighters, which in turn also raises the radicalization rate. Since it has been estimated that, for instance, between 1,500 and 4,000 Britons have received training in terrorist camps[27], it is difficult to accept the number of 945 as a workable amount of all Europeans who have been trained or who have fought abroad.[28] 

Unfortunately, there are not enough open-source based data with more reliable estimates of the total amount of foreign fighters. It can only be speculated that it must be multitudes of the current estimate used. Given this obvious limitation, how then can we get a better understanding of the involvement of foreign fighters in terrorist attacks compared to the overall number of foreign fighters? For this Research Note we looked at three cases, namely Afghanistan (1980s), Bosnia (1990s) and Somalia (2000s). The sample could have admittedly been larger if Chechnya, Iraq or Yemen had also been included. The result is a typology of foreign fighters’ post-conflict behaviour. There is no denying that it simplifies the complicated picture of foreign fighters. Nevertheless it provides a framework to structure analysis and to identify knowledge gaps in current research.


Results from Three Case Studies

In this Research Note, there is not enough space to discuss the complete results of these historical case studies. For that readers can turn to a recent ICCT-paper co-authored with Edwin Bakker.[29] One result discussed here is that foreign fighters, based on their post-conflict behaviour, can be divided in five types:

Table 2: Typology of Returned Foreign Fighters

(i) the martyr: a foreign fighter who joins a conflict and is killed on the battlefield. The martyr will pose no further risk to the country of origin unless the martyrdom itself is used as recruiting tool.

(ii) the veteran: an experienced fighter who continues fighting in other theatres of conflict. The veteran sees jihad as a way of life. While the veteran is a risk to people in conflict zones, he is no risk to the country of origin in the West.

(iii) the recruiter: the recruiter is usually a former foreign fighter who returned home to recruit others to fight, often quite successfully because of his “street credibility”. However, it must be noted that the role of the recruiter has possibly somewhat changed in recent years.[30] Generally speaking, recruiters are not directly involved in terrorist activity but are frequently seen as spiritual guides to future terrorists. They are an indirect risk by constantly ‘feeding’ the local jihadist community.

(iv) the reintegrated fighter: he is the one-time foreign fighter. After the conflict or his role in it has ended, the reintegrated fighter will return and resume his pre-departure life or will at least not be involved in terrorist activity.[31] Some of these fighters might have been driven by a genuine desire to help the oppressed or might have been motivated by the search for adventure, often without profound knowledge of religion. This fighter might return home disillusioned because the conflict was not what he expected it to be. These fighters are usually no risk to the country of origin. It should be noted the fighter could also integrate in the country he fought in, as happened with some of the Bosnia veterans.

 (v) the terrorist: when he comes into contact with terrorist networks in conflict zones, he becomes convinced that it is not only a priority to fight for the oppressed abroad, but also to target the country of origin. This type of foreign fighter – not infrequently converts to Islam - undergo the most fundamental shift in identity and norms and pose a direct threat to the country of origin.

Now that a typology of foreign fighters has been established, the question arises if it is possible to provide estimates of the proportions of these types. A first observation is that our knowledge of the different categories is uneven. Three of these five categories are better understood: the martyr, the terrorist and the recruiter. Cases of martyrdom are often reported by the foreign fighter movements themselves in online martyrdom notices. The terrorist is directly linked to an attack and can therefore be expected to gain high exposure. The recruiter is often under surveillance by intelligence authorities.[32] Much less is known about the veteran and the reintegrated fighter.

Despite the difficulty to give rough estimates about the number of foreign fighters, the anecdotal evidence that formed the basis of the three case studies suggest that the total number of martyrs, terrorists and recruiters comes nowhere close to the total number of foreign fighters. Simply put, thousands of Western Muslim fighters have fought abroad while only a few dozen of them became involved in terrorist activity at home. One tentative finding is that the ‘hard-liners’ are often not the ones who return but rather the ones who continue to fight somewhere else. They exhibit no motivation whatsoever to return because they have taken, as they say, the path of jihad. Another observation that was evident in all three case studies was the major influence of ‘recruiters’: foreign fighters who returned to recruit others. Many of the Afghanistan veterans who relocated to European cities like London were pivotal in subsequent foreign fighter mobilisations.[33]

Finally, it must be said that these categories are not fixed, unchanging nor the only options. Sometimes they might even overlap. However, they are useful for a better understanding of the different types of threats posed. Different types, in turn, ask for different approaches to counter it. Thus, they should be seen as lenses and not as a rigid depiction of an ‘empirical reality’.


Second Approach: Involvement of Foreign Fighters in 26 Terrorist Plots in Europe

As part of the second approach, a new list was compiled, consisting of 26 plots with a total of 123 individuals involved (see Appendix I). Of these 123 individuals in the database, just over half (68 or 55.3%) could be categorized as Western.[34] Employing the definition used by Hegghammer that includes both foreign fighters (those who fight in conflict zone) but also foreign ‘trainees’ (those who train at a terrorist training camp), we find 33 cases of a foreign trip plus two cases of individuals who tried to join a militant group but failed to do so and returned home.

This means that 33 out of 123 (26.8%) of all the individuals can be categorised as Western foreign fighters according to the common definition.[35] In other words, more than a quarter of terrorists involved in the most important terrorist plots in the West can be categorised as Westerners who went abroad either for terrorist training or fighting. However, if we look at the distribution between fighting and training, we see that 11 of them (33.3%) were foreign fighters who joined an insurgency in a conflict zone while 22 (66.7%) were foreign fighters who went to a training camp. These individuals almost exclusively went to training camps run by Al Qaeda, mainly in Pakistan or Afghanistan, or are confirmed to have met with high-ranking Al Qaeda figures while abroad. Thus, according to the definition of foreign fighting used in this research project, only 11 out of 123 (8.9%) individuals can be categorised as Western foreign fighters. This would rather point to a rate of 1 out of 11.

There are some other ways of looking at this data that could be useful. In 13 of the 26 plots (50%), there was at least one individual who went abroad to either fight or train. In 5 of those 13 cases (38.5%) of individuals who went abroad, the motivation was because at least one individual joined an insurgency while in the other 8 cases (61.5%) it was because at least one individual went to a training camp. Therefore, 5 of the 26 plots (19.2%) had at least one individual involved who can be defined as a Western foreign fighter. 8 of the 26 plots (30.8%) had a link to a Western individual who went to a terrorist training camp.[36]


The Lethal Plots

A final calculation will look at the relation between lethal plots and foreign fighting or training. Of the plots in this database, 10 resulted in injuries or fatalities other than the perpetrators themselves.[37]. Of the 61 individuals involved, seven were Western foreign fighters or trainees (11.5%). This percentage is considerably lower than the 26.8% of Western foreign fighters and trainees in all the plots (33 out of 123).

Contrary to what is often argued, this could suggest that Western foreign fighters (and trainees) do not make more lethal operatives than non-foreign fighters. However, among these plots is an example reminding us of the danger of a link to foreign training: two of the four London Bombers, Mohammed Siddique Khan and Shehzad Tanweer, trained in Pakistan prior to the attacks. While this plot clearly had a foreign link, both of these men cannot be categorized as foreign fighters but should rather be seen as foreign trainees. If we distinguish between foreign fighters and foreign trainees in all these ten plots, we see that all of these seven individuals went to training camps and none of them actually participated in traditional insurgencies. Therefore, not a single case of ‘foreign fighting’ as defined here has been involved in the most lethal attacks in Europe since 1994.

It must be noted that these findings should not be seen as the result of statistically significant data. This approach calculated the ratio of former foreign fighters involved only in the most serious jihadist-inspired terrorist plots and attacks in Europe since 1994. Further criticism on this database could address its limited scope (only Europe, only 26 plots), its reliance on newspaper articles and secondary literature (which might have led to wrong categorisations), and its working definition of ‘Western’. That is why the presented rates should certainly not be interpreted as the ‘true’ rates, countering findings from previous works. It is, however, an attempt to further build on previous works and critically examine some assumptions that inform our current view on the issue.


The two approaches used in this Research Note show that the extent to which Western foreign fighters have been directly involved in terrorist activity in Europe in the past is rather limited. Again, it cannot be said often enough that this highly depends on the definitions used. In this Research Note, we summarized findings from three past instances of foreign fighting. The main conclusion from these three case studies is that there is no archetype of the foreign fighter. Rather, based on post-conflict behaviour, they can be divided into five categories: the martyr, the veteran, the recruiter, the reintegrated fighter and the terrorist. These are very simple categories and they do not say much about the motivation of individual foreign fighters nor can they be used to predict who will end up in which category. Further research is necessary to try to understand why and how out of a large group of foreign fighters, some become terrorists while others peacefully reintegrate. A difficult question is to what extent this is caused by internal factors (motivation of the foreign fighter, religiosity, social alienation and so on) and what is caused by external factors (recruitment, radicalization, pressure, and obstructing factors that hinder reintegration). To answer that, however, is beyond the scope of this Research Note.

What this Research Note hopefully did show is that the presence of Western foreign fighters in the most serious jihadist attacks and plots in Europe since 1994 has been limited and is much lower than is often feared. When there is a foreign link, it is, in most cases, a link to a terrorist training camp rather than to actual foreign fighting pur sang: defensive jihads in Afghanistan or Bosnia where a civil conflict was already ravaging the country before the influx of foreign fighters (which often made it worse). In European lethal plots, this presence was even lower, which makes the assumption that foreign fighters have proved to be more lethal operatives than those who did not fight questionable. However, to build this database (see Appendix), much information on the included perpetrators was taken from open sources, such as newspaper articles (which are not very reliable). Thus, in order to be able to make any substantial claims on this issue, more in-depth research is needed. Again, a phase of refining the definitions, methodologies (a larger and more reliable database) and sources is needed to make any authoritative claims, especially when talking about proportions of foreign fighters subsequently involved in terrorist activity at home. However, this Research Notes has pointed at some avenues for further research and has hopefully raised awareness that careful reconsideration of the assumptions that currently form the basis of our understanding of foreign fighters is necessary.

Finally, a number of observations with regard to the current situation in Syria and Iraq need to be made. As explained in the introduction, extrapolating the research outcomes to the current situation cannot be justified. The sole possibility is to assess the current situation in order to identify issues that require further research. The following observations should thus be carefully approached. The initial phase of the conflict in Syria appeared to share many characteristics with the cases that in this research have been labelled classical examples of foreign fighting: Afghanistan and Bosnia (more than Somalia). As Brian Jenkins explained in a testimony in November 2013, ‘(s)ome of the jihadists are determined to fight, but others seem to be little more than jihadi tourists who stay out of harm’s way while taking photos of themselves and boasting to their friends back home on social media’.[38] This clearly echoes stories about past conflicts in which foreign fighters were sometimes called ‘Gucci soldiers’ or only turned up for the fight during their summer breaks, like in Afghanistan.[39] Until recently, these fighters in Syria were viewed as a greater problem than other former foreign fighters because of the proximity to the West and their volume [40], not because there was some kind of assumed ‘qualitative’ difference between those fighters and their historical counterparts. Jenkins continues by saying that ‘Syria’s jihadist groups may not be looking for a fight with Western countries, which are also opposed to Assad. This attitude could change if the West or Western-backed rebels move against the jihadists during a post-Assad civil war’.[41]

Unfortunately, his prediction seems to describe what has happened in the summer of 2014. While Western governments initially supported the rebels and have not backed down from arming them, much has changed.[42] This culminated in US-led air strikes (backed by Arab nations) on IS-fighters in September 2014.[43]This transformed the Islamic rebel groups into direct enemies of Western (and Arab) governments. On September 13, 2014, spokesman for the White House Josh Earnest declared that ‘[t]he United States is at war with ISIL in the same way that we are at war with al-Qaeda’.[44]

The rhetoric used by rebel groups has also dramatically changed. Jabhat al-Nusra, which has mainly focused on Syria and rejected mergers with IS in the past, has now allegedly joined forces with the latter and threatened the West to ‘pay the highest price’ for its actions.[45] Clearly, the terms of engagement on both sides have changed. This does not bode well for the future.


About the Author: Jeanine de Roy van Zuijdewijn works as a Researcher at the Centre for Terrorism and Counterterrorism – The Hague. This Research Note is based on her Master thesis completed at Utrecht University in January 2014.

Appendix I - the Database [46]


Black: individuals who did not fulfill the criteria of ‘Western’ or could not be categorized as foreign fighters or trainees.

Green: individuals who fulfilled the criteria of ‘Western’ and could be categorized as foreign fighters or trainees.

Blue: activity of this Western individual can be categorized as training.

Red: activity of this Western individual can be categorized as fighting.

Orange: failed attempt by a Western individual to train/fight.



[1] Richard Barrett, “Foreign Fighters in Syria”, The Soufan Group, 6 June 2014,http://soufangroup.com/foreign-fighters-in-syria/.

[2] “Islamic State Crisis: ‘3,000 European jihadists join the fight’”, BBC News, September 26, 2014, http://www.bbc.com/news/world-middle-east-29372494.

[3] Numbers based on an interview with Peter Neumann, expert at the International Centre for the Study of Radicalisation and Political Violence; in Edith M. Lederer. “Expert: over 12,000 foreign fighters in Syria”, September 8, 2014, http://bigstory.ap.org/article/expert-over-12000-foreign-fighters-syria. Numbers on the Netherlands and the Russian Federation are from June 2014, in: Richard Barrett, “Foreign Fighters in Syria”, The Soufan Group 6, June 2014,http://soufangroup.com/foreign-fighters-in-syria/.

[4] Evan Kohlmann and Laith Alkhouri, “Profiles of Foreign Fighters in Syria and Iraq”, CTC Sentinel, September 29, 2014, https://www.ctc.usma.edu/posts/profiles-of-foreign-fighters-in-syria-and-iraq.

[5] Brian Michael Jenkins, “International Terrorism: A New Mode of  Conflict,”  in:  David Carlton and Carlo Schaerf (Eds.), International Terrorism and World Security, London: Croom Helm, 1975,  p.15.

[6] Brian Jenkins, The New Age of Terrorism, RAND Report, 2006, p.119, http://www.prgs.edu/content/dam/rand/pubs/reprints/2006/RAND_RP1215.pdf.

[7] “ISIS militants post grisly images of mass killing in Iraq”, CBS News, http://www.cbsnews.com/news/iraq-conflict-isis-militants-post-grisly-images-of-mass-killing/June 14, 2014, http://www.cbsnews.com/news/iraq-conflict-isis-militants-post-grisly-images-of-mass-killing.

[8] See, for instance, the recently launched plan of British PM David Cameron, Patrick Wintour, “David Cameron shelves move to ban British jihadis returning to UK”, The Guardian, September 1, 2014, http://www.theguardian.com/politics/2014/sep/01/anti-terror-policy-legal-political-opposition-jihadis-uk.

[9] Josh Halliday and Andrew Sparrow, “Former MI6 counterterrorism-chief warns against rush to overhaul UK laws”, The Guardian, August 25, 2014; http://www.theguardian.com/uk-news/2014/aug/25/counter-terrorism-laws-warning-mi6-chief.

[10] Macer Hall, “'Barbaric' Islamic State terrorists have already attempted SIX attacks in Europe”, Express, September 9, 2014, http://www.express.co.uk/news/uk/508458/Islamic-State-terrorists-have-already-attempted-SIX-attacks-in-Europe.

[11] Thomas Hegghammer. ‘Should I Stay or Should I Go? Explaining Variation in Western Jihadists’ Choice between Domestic and Foreign Fighting’, American Political Science Review,Vol. 107, No. 1 (February 2013), pp.1-15; Thomas Hegghammer. ‘The Rise of Muslim Foreign Fighters: Islam and the Globalization of Jihad’, International Security, Vol. 35, No. 3 (Winter 2010/2011), pp.53-94; David Malet. Foreign Fighters: Transnational Identity in Civil Conflicts, New York: Oxford University Press, 2013; Petter Nesser. ‘Chronology of Jihadism in Western Europe 1994-2007: Planned, Prepared, and Executed Terrorist Attacks’, Studies in Conflict & Terrorism, Vol. 31, No. 10 (2008), pp. 924-946; Petter Nesser. ‘How did Europe’s Global Jihadis Obtain Training for their Militant Causes?’, Terrorism and Political Violence, Vol. 20, No. 2 (April 2008), pp.234-256; Aaron Y Zelin. ICSR Insight: Up to 11,000 Foreign Fighters in Syria; Steep Rise Among Western Europeans, The International Centre for the Study of Radicalisation, December 17, 2013, http://icsr.info/2013/12/icsr-insight-11000-foreign-fighters-syria-steep-rise-among-western-europeans.

[12] D. Malet, Foreign Fighters, p. 9.

[13] Only focusing on Europe would have yielded too few results, given the fact that most foreign fighters in, for instance Afghanistan, came from the United States.

[14] Petter Nesser.‘Chronology of Jihadism in Western Europe 1994-2007: Planned, Prepared, and Executed Terrorist Attacks’, Studies in Conflict & Terrorism, Vol. 31, No. 10 (2008), pp. 924 - 946.

[15] Edwin Bakker. Jihadi Terrorists in Europe: their characteristics and the circumstances in which they joined the jihad: an exploratory study, The Hague: Netherlands Institute of International Relations Clingendael, 2006, p.2.

[16] Barak Mendelsohn. ‘Foreign Fighters – Recent Trends’, Orbis, vol. 55, no.2 (2011), pp.189-202, p.193.

[17] B. Mendelsohn. ‘Foreign Fighters – Recent Trends’, op. cit., p.193. The distinction can also be found in the earlier mentioned work of Marc Sageman: Understanding Terror Networks (2004), who excludes ‘Muslims fighting for the “liberation” of Kashmir or Chechnya, for these seem to be straightforward jihads, like the former Afghan or Bosnian jihads as defined by Azzam’ from his ‘global Salafi mujahedin’ population. Sageman is right to point at a difference between terrorists and ‘traditional’ mujahideen. There is a clear difference in the target selection, the legitimacy and the modus operandi of both groups.

[18] Terms like ‘Western’, ‘Westernised’ and ‘Western values’ should normally be applied with due caution. Some even argue that there is no such thing as specific ‘Western’ as in ‘Western values’. However, debates about the assimilation and integration of immigrants are not part of this research. The aim here is to understand the risk coming from Western foreign fighters, where ‘Western’ serves to point to ‘those coming from within’ rather than a threat coming from those who adhere to so-called ‘Western values’. The criteria are therefore aimed at delineating what can be called ‘within’ and should not be regarded as pretending to say anything about the relative merit of cultural values, assimilation and other issues relating to (im)migrants or cultures.

[19] P. Nesser.‘Chronology of Jihadism in Western Europe 1994-2007’, p.926. - Nesser’s list of incidents was combined with information on the plotters as reported in the work of Edwin Bakker and Frazer Egerton; see Edwin Bakker. Jihadi Terrorists in Europe: their characteristics and the circumstances in which they joined the jihad: an exploratory study, The Hague: Netherlands Institute of International Relations Clingendael, 2006, and Frazer Egerton. Jihad in the West: The Rise of Militant Salafism, New York: Cambridge University Press, 2011.

[20] Although almost all the ‘Category 1’ plots of Nesser were included, I chose to exclude two plots and include one extra. The first excluded plot is the arrest of two French-Algerians by the French police in January 2004 that were claimed to plan to use ricin. These individuals are reported to be relatives of Menad Benchelalli of the Chechen Network but their identities have not been revealed. Another excluded plot is the arrest of five persons in Rovigo, Italy, because the police found bombs during a regular raid looking for illegal immigrants. Maps of NATO bases and central London were found, but no real plot was discovered. One plot that I chose to include was the arrest of Kamel Bourgass in the United Kingdom, who possessed poison recipes and bomb-making instructions. During a police raid, Bourgass killed one police officer. Although Nesser has some doubts about the plot, calling it a Category 2 plot while saying it is difficult to assess the ‘realities of this particular case’, the plot is included in the databases of both Bakker and Egerton. Because Bourgass was responsible for the killing of a police officer, I chose to include the plot, although the fatality is not counted.

[21] William Rosenau and Sara Daly. ‘American Journeys to Jihad: U.S. Extremists and Foreign Conflicts during the 1980s and 1990s’, CTC Sentinel, Vol. 3, No.8 (2010), pp.17-20, p.17.

[22] J.M. Berger. Jihad Joe: Americans who go to war in the name of Islam, Dulles: Potomac Book, Inc., 2011, pp.xi. - Berger conducted about one hundred interviews with a variety of actors: Muslims radicals, former jihadists and Al-Qaeda members, current and former intelligence, law enforcement, military and diplomatic officials, academics and relatives and associates of former jihadists.

[23] Th. Hegghammer. ‘Should I Stay or Should I Go?’, p.5.

[24] Idem, p.10.

[25] See, for instance, Hanna Nomm, Foreign Fighters in Syria: A Danger to the West?, The Henry Jackson Society, November 26, 2013, http://henryjacksonsociety.org/2013/11/26/foreign-fighters-in-syria-a-danger-to-the-west/.

[26] The author of this Research Note also first failed to stress that this was a maximum rate. Other examples are the United Kingdom Counter – Terrorism Home Affairs Committee, which stated that Hegghammer found “that on average, one in nine foreign fighters returned home to take part in a domestic terror plot”. -  The United Kingdom – Parliament, Counter-Terrorism Home Affairs Committee, Foreign Fighters, http://www.publications.parliament.uk/pa/cm201314/cmselect/cmhaff/231/23105.htm, May 9, 2014.

[27] This might, in turn, be a case of overestimating the numbers of UK residents who trained in terrorist camps.

[28] Ben Leapman. ‘4,000 in UK trained at terror camps’, The Telegraph, July 15, 2007, http://www.telegraph.co.uk/news/uknews/1557505/4000-in-UK-trained-at-terror-camps.html

[29] Jeanine de Roy van Zuijdewijn and Edwin Bakker. Returning Western Fighters: The case of Afghanistan, Bosnia and Somalia, ICCT Background Note, June 2014, http://www.icct.nl/publications/icct-papers/returning-western-foreign-fighters-the-case-of-afghanistan-bosnia-and-somalia

[30] Prior to 9/11, these individuals enjoyed relative freedom but after these attacks their activities are more closely monitored and constrained.

[31] This is a group where psychological problems such as PTSD could occur. While these fighters form no security risk in the sense of involvement in terrorist plots and attacks, ‘reintegrated’ fighters could certainly pose a risk to themselves and their direct surroundings.

[32] Algemene Inlichtingen- en Veiligheidsdienst (AIVD), Recruitment for the jihad in the Netherlands: from incident to trend, The Hague: AIVD, 2002.

[33] Mohammed Hafez. ‘Jihad after Iraq: lessons from the Arab Afghans’, Studies in Conflict & Terrorism, Vol. 32, No.2 (2009), pp. 73-94.

[34] Using the criteria as mentioned in the previous section and the definition of Western countries as the 28 EU member states, Western European states that are not member of the EU, the United States, Canada and Australia.

[35] Note that the 33 only related to Western cases.

[36] In the original research, two corrections were applied. Two plots disproportionally influenced the results: The Madrid Bombings and the Chechen Network. The Madrid Bombings accounted for almost a quarter of all individuals in the database (27 out of 133) of which none had fought or trained abroad. The Chechen Network, in turn, accounted for more than half of the entire number of Western foreign fighters in the database (6 out of 11). Thus, calculating without these two plots results in a number of 27 out of 90 (30%) having either trained or fought abroad, of which 22 went to training camps and only 5 (5.6%) can be categorised as Western foreign fighters. Applying these two exceptions results in a ratio of 1 out of 17.

[37] It should be noted that 10 out of 26 is not a reflection of the overall rate of jihadist plots that are successfully executed and result in casualties. Because the database only contained plots until 2007, I included five post-2007 plots that resulted in deaths or injuries. On the other hand, this does mean that the database contains at least the most dangerous/lethal plots that can be seen as the ones with the highest security risk. A second remark that should be made is that one of the perpetrators of plot 11 – Kamel Bourgass – killed a police officer when his house was being raided. That is, however, not counted as a fatal plot because this was no terrorist attack (or even premeditated murder) but lethal violence upon being arrested. 

[38] Brian Michael Jenkins, The Role of Terrorism and Terror in Syria’s

Civil War, RAND Office of External Affairs, November 2013, http://docs.house.gov/meetings/FA/FA18/20131120/101513/HHRG-113-FA18-Wstate-JenkinsB-20131120.pdf.

[39] See, for instance, Evan Kohlmann. Al-Qaida’s Jihad in Europe: The Afghan-Bosnian Network, Oxford: Berg Publishers, 2004, p.8 and Jason Burke. Al-Qaeda, London: Penguin Books, 2007 [revised edition], p.76.

[40] Brian Michael Jenkins, The Role of Terrorism and Terror in Syria’s

Civil War, RAND Office of External Affairs, November 2013, http://docs.house.gov/meetings/FA/FA18/20131120/101513/HHRG-113-FA18-Wstate-JenkinsB-20131120.pdf.

[41] Idem.

[42] Ernesto Londoño and Greg Miller, “CIA begins weapons delivery to Syrian rebels”, Washington Post, September 11, 2013, http://www.washingtonpost.com/world/national-security/cia-begins-weapons-delivery-to-syrian-rebels/2013/09/11/9fcf2ed8-1b0c-11e3-a628-7e6dde8f889d_story.html.

[43] Martin Pengelly, “Arab Nations join Syria strikes as Al Nusra front threatens retaliation”, The Guardian, September 27, http://www.theguardian.com/world/2014/sep/27/obama-us-isis-syria-iraq-coalition-kurds-jets-strike.

[44]“ US: We are at war with Islamic State group”, Al Jazeera, September 13, 2014, http://www.aljazeera.com/news/middleeast/2014/09/us-are-at-war-with-islamic-state-group-201491323051540963.html.

[45] John Beck, “Syrian Al-Qaeda Leader Threatens Attacks on West”, Vice News, September 29, 2014,


[46] Readers can request a list of sources by sending an e-mail to: < [email protected] >.

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.


Perspectives on Terrorism is  a journal of the Terrorism Research Initiative and the Center for Terrorism and Security Studies

ISSN  2334-3745 (Online)

Disclaimer, Terms and Conditions