How Dangerous Are Domestic Terror Plotters with Foreign Fighter Experience? The Case of Homegrown Jihadis in the US

by Christopher J. Wright


Do Americans who return home after gaining experience fighting abroad in Islamist insurgencies pose a greater risk than homegrown jihadi militants with no such experience? This study looks at the net effect of foreign fighters on domestic plots in the US by disaggregating data from the Jihadi Plots in the West dataset. It finds that the presence of a returnee decreases the likelihood that an executed plot will cause mass casualties. Also, plots carried out with American returnees from Islamist insurgencies abroad decrease the likelihood that a plot will come to fruition. This may be because the presence of a known foreign fighter increases the likelihood of detection and disruption by law enforcement officials. The US as a case study may not be generalizable to other Western countries because of its unique geographic position and its longer experience of prosecuting would-be foreign fighters.

Keywords: Foreign fighters; United States; homegrown terrorism; jihadis.


How great of a threat do would-be American jihadis pose to their home country? And do Americans who return home after gaining experience fighting abroad in Islamist insurgencies or attending terror training camps pose a greater risk than other jihadi militants? This article attempts to answer those questions by looking at those with deep ties to the US who (for some reason) decided to go abroad to fight for various Islamist groups, only to return home with what is often assumed an even greater militancy than before. Of even greater worry is the notion that not only has their commitment level to attacking their homeland increased after their experience as foreign fighters, but that they also may bring back a skill set which makes it more likely that plots go from planning to execution. This same skill set, it is hypothesized, also leads to greater numbers of casualties. These veteran returnees, then, appear to be more dangerous than non-veteran would-be domestic jihadis.

This is the conclusion reached by Hegghammer in his seminal 2013 study on foreign fighters and Western terror plots.[1] Hegghammer’s study is seminal because it was both timely and appeared to have had an actual impact in policy circles. It is timely because it was published one year before the leader of the Islamic State of Iraq and Syria (ISIS) declared himself Caliph and the Islamic State as the Caliphate. It is impactful as it came at a time when intelligence agencies and law enforcement officials were noticing what seemed to be an extreme increase in the number of Muslims raised in the West making their way to Syria 
to join ISIS. Given the apparent large number of Westerners going to Syria, it stood to reason that some of them would eventually come home. Hegghammer’s analysis suggested that these returnees might be a greater danger than when they left.

Other research has led to similar conclusions.[2] For instance, Byman’s 2015 study of veteran returnees suggests that they, like their Western counterparts, may be more dangerous than those without foreign fighting experience.[3] Nilson’s study of Swedish veteran jihadi foreign fighters of the Afghan, Bosnian, and Syrian conflicts claims that although such fighters may not be more skilled at conducting acts of terrorism, as others have suggested, that they are more dangerous because they may help normalize jihadi thinking that attacking in the West is legitimate and thus lead to more plots on domestic soil.[4] Kenny’s case study of jihadi plots in the UK and Spain concludes that cell members developed important skills by attending terrorist training camps abroad. When combined with the specific geographic, cultural, and social knowledge only a local would have, plots involving those with longtime ties to the areas in the West where the plot was launched were found to be more effective. [5] Similarly, Vidino’s study found that explosives training abroad was key to more lethal plots. [6] A more recent examination by Hegghammer and Nesser finds that in recent years plots involving foreign fighters are executed at a lower rate than plots without them. However, the same study shows that executed plots including foreign fighters were far more deadly on average than those without foreign fighters. [7]

This growing body of research, combined with media reports have led governments and think tanks to study the phenomenon as well.[8] Public conclusions drawn by these analyses might be summed up nicely in the title of a Brookings policy paper, “Be Afraid. Be A Little Afraid: The Threat of Terrorism from Western Foreign Fighters in Syria and Iraq.”[9] In 2014, President Obama addressed the UN General Assembly and urged member states to do more to address the growing problem. In February 2015, fears of radicalized Westerners led the White House to host a three-day summit on Countering Violent Extremism (CVE).[10] UN Security Council Resolution 2178, adopted in September of 2014, “requires states to prevent and suppress recruiting, organizing, transporting, and equipping of [foreign terrorist fighters].”[11] Worrying about returnees is not just an academic exercise: it is now the province of legislators and policymakers on a global scale.

One important exception to the literature is the work of de Roy van Zuijdewijn, whose study of European jihadis makes a conceptual distinction between Westerners who had engaged in traditional insurgencies (foreign fighters) and those that had attended terrorist training camps (trainees).[12] While I do not adopt de Roy van Zuijdewijn’s specific definition here, distinguishing between types of foreign fighters is helpful because much of what is driving the concern of policy makers is the notion that citizens of Western countries will travel abroad, become even more radicalized, learn skills which might be useful in terrorist attacks, and then return home to commit acts of violence on a greater scale than had they simply stayed home. With this distinction in mind, de Roy van Zuijdewijn’s research, “could suggest that Western foreign fighters (and trainees) do not make more lethal operatives than non-foreign fighters.” [13]

As I conceive it, these two categories of jihadis – foreign nationals who travel internationally to commit acts of terrorism, and domestic citizens who return home after gaining jihadi training abroad – should be treated as related but separate phenomena which may require separate policies in addressing them. Because this study begins with the same dataset used by Hegghammer, I adopt his definition of foreign fighters as any jihadi involved in any military activity, using any tactic, against any enemy, “so long as it occurs outside the West.” [14] Thus, a foreign fighter would both include a Saudi fighting in Iraq and a Belgian fighting in Syria. By would-be jihadi, I mean any person who has made concrete plans to commit acts of violence in furtherance of the Salafi-jihadi ideology, whether they are attempting to travel abroad (successful or not) to become a foreign fighter or who makes the determination to stay home and commit acts of terror domestically. By homegrown jihadi, I mean those who have been raised in the West, become naturalized citizens of Western countries, or who have spent substantial time and who have substantial ties to a Western country but who have adopted the Salafi-jihadi ideology and are would-be jihadis. By veterans, I mean foreign fighters who are no longer engaged directly in fighting outside the West. Veterans could include both Westerners and non-Westerners alike. By returnee, I mean only those homegrown jihadis who are veteran foreign fighters and who have returned to their country of origin in the West. An example of a returnee would be a German citizen who joins a jihadi group in Afghanistan only later to return to Germany. Non-Western jihadi veterans who may move to the West are not treated as returnees. Thus, while Muhammad Atta – one of the leaders of the 9/11 plot — would be treated as a veteran foreign fighter, as I conceptualize it he would not be counted as a returnee. The rest of this article shows how using these definitions and disaggregating data on returnees specifically from the more general foreign fighters yields very different result as to the effectiveness of plot execution and the number of casualties caused by those plots.

Quantifying Homegrown Terrorists

Using the Jihadi Plots in the West and Foreign Fighters Observation datasets, I first looked at all jihadi plots carried out on US soil from 1990 – 2010.[15] I then looked at each individual and coded them as homegrown, foreign, or unknown. A simple internet search was done to determine background information on each of the plotters. Both media reports and sources such as Wikipedia were treated as authoritative. While the latter source might be seen as problematic, there is little reason to believe that biographical information, such as country of origin or citizenship status, would be controversial enough to be open to debate amongst those who can edit Wikipedia pages.

A plotter was coded as “homegrown” if he or she was clearly a US citizen, whether born in the US or through naturalization. Further, those who were not US citizens but who had clearly been raised in the US without going through the formal naturalization process were also deemed homegrown. Such is the case, for instance, of several of the convicted Fort Dix plotters. The assumption here is that regardless of citizenship status, those raised from childhood in the US have adopted, to some extent, the norms and values of their host society. This method of coding is similar to the one of de Roy van Zuijdewijn who codes “Westerners” based on citizenship, age of naturalization, or number of years in Western countries prior to terrorist activities.[16] Those who immigrated to the US as adults but who never naturalized as US citizens are treated here as foreign.

One problem encountered while coding for homegrown jihadis were cases in which a plotter was born in the US to foreign parents, and therefore become automatically a citizen, but raised abroad only to return to the US in adulthood. For instance, this is the case of Abdul Rahman Yasin, one of the first World Trade Center plotters. He was born in Indiana while his father was a graduate student, but was raised in Iraq. Yasin used his US passport to come “home” as an adult to help carry out the attack. In such cases I coded the plotter as homegrown, although they may be rightfully seen as part of a separate category. I did so, based on the notion that possession of a US passport alone makes such a plotter of greater concern, because it is more difficult to stop them in our first line of defense – at the border.

Another problem arose when encountering those who immigrated to the US as adults, never became citizens, but who were here for many years before becoming involved in jihadi plots. In such cases it is not clear when the individual became radicalized, and thus how to code them for this article.[17] Here, I simply treated such individuals as foreign.

This subset of the JPW dataset yielded 95 perpetrators involved in 33 plots against target in the United States from 1990 to 2010. Of those, 47, or roughly half, were homegrown jihadis – these were the domestic plotters who were US citizens or who had been raised in the US. Of the remaining plotters, 44 were coded as foreign – those jihadis who were not US citizens or who had not been raised in the US (See Table 5). Four were left uncoded for lack of information.[18]

Table 1: Background of 95 Perpetrators of Plots in the United States

Number of jihadi plots in the US 1990 - 2010

Total number of US jihadi plotters 1990 - 2010

Homegrown jihadis in the US

1990 – 2010

(% total)

Foreign jihadis in the US 1990 – 2010 (% total)

Returnees: homegrown plotters with foreign fighter experience



47 (49%)

44 (46%)

12 (13% of total / 25% of homegrown jihadis)


From this subtotal, I then derived homegrown “returnees” by looking at the total number of homegrown jihadis and calculating how many of them had been coded as having “foreign fighter experience” in the JPW dataset. Of the 47 homegrown jihadis, only 12 of them were returnees – those who were US citizens or who had been raised in the US and who are known to have traveled abroad, gained some experience as a foreign fighter or attended a terrorist training camp, and then returned home to plot acts of violence domestically. These 12 known returnees represent only about 13% of all jihadi plotters in the US, but represent about 25% of homegrown jihadis. Thus we can safely say that from the years 1990 – 2010 about one in four homegrown jihadi plotters were returnees.

Since the fear is that these returnees are more likely to: a) have their plots come to fruition; and b) cause more deaths; I then looked at the number of casualties inflicted by plots carried out by purely domestic jihadis vs. those plots which involved returnees. I exclude those plots which were purely foreign in nature – those plots in which none of the perpetrators had any deep ties to the United States. Only six of the 33 plots can be said to be entirely foreign or international in character – lacking any participant with deep ties to the US. However, these six include the 9/11 plot which accounts for the vast majority of deaths at the hands of jihadis in the 20 year period covered in this study. Of the 2999 killed in domestic jihadi attacks, 9/11 accounts for 2977 or 99% of them. Other excluded plots include that of Richard Reid, the so-called “shoe bomber”, and the LAX plot because the lone actors involved were not homegrown. Since this article is concerned with how returnees might affect the effectiveness of domestic terror plots, these and other plots with no US connection are excluded. Therefore, 27 plots were included in this portion of the study.

Of these 27 plots against targets in the US which included at least one homegrown jihadi, 9 of them – or about 33% — involved returnees (see Table 2). Only 5 of the 27 – or 19% of the total – plots ever came to fruition and were executed. These five executed plots led to the deaths of 22 people. But a returnee was involved in only one of the plots in which there were actual victims. This represents 4% of the total plots, or 20% of the plots that were executed. The other four plots, those in which no returnee was involved, accounted for 95% of deaths.

The solitary homegrown plot involving a returnee in which casualties were inflicted was the case of Abdulhakim Muhammad. In Muhammad’s case that victim was Private William Long, an Army recruiter in North Little Rock. Also injured, but not killed, was Private Quinton Ezeagwula. Muhammad had gone to Yemen to study Arabic and later claimed that he had been in contact with al Qaeda in the Arabian Peninsula (AQAP). Muhammad, a convert to Islam who changed his name from Carlos Leon Bledsoe, was born in Tennessee and claims that he was committed to violent jihad from the moment of his conversion.[19] This represents the only case in the twenty years covered by this study in which a homegrown jihadi was radicalized domestically, went abroad to seek out foreign jihadis, and then returned to the U.S. to actually commit an act of violence in which someone was killed. There is also no evidence to suggest that Muhammad had actually taken up arms nor that he had been trained in any way by AQAP. All other executed plots were either foreign in character (e.g. 9/11) or completely domestic without the participation of a single returnee.

Table 2: Plots and Fatalities Involving Homegrown Terrorists and Returnees to the US

Number of plots in the US with

homegrown jihadis

Number of plots involving returnees

(as % of total)

Total number of deaths in homegrown plots

Number of homegrown plots executed

(as % of total)

Number of executed plots with returnees

(as % of total)

Number of deaths in plots with returnees

(as % of total)

Number of deaths in plots with no returnees




5 (19%)

1 (4%)

1 (5%)

21 (95%)


But what of these other homegrown plots which were executed without the assistance of a returnee? Of the 21 other victims in these plots in which a homegrown jihadi was involved, 13 of those were killed in a single attack at the hands of Nidal Malik Hasan in the mass murders at Fort Hood, Texas. Hasan is a classic homegrown jihadi. Born and raised in Arlington, Virginia to parents from Palestine, Hasan had served as an enlisted soldier in the Army prior to earning his medical degree and being commissioned as an officer. Hasan became radicalized sometime after 9/11. Although some of his fellow soldiers reported some unusual discussions on Hasan’s part that might have been construed as sympathetic to violent jihadism, the red flags were not enough to prevent him from turning on his fellow soldiers, killing 13 in the process. Law enforcement and media reports suggest that Hasan was in contact with American born cleric Anwar al-Awlaki, a spiritual leader in AQAP.[20] However, the extent of Hasan’s relationship with AQAP remains unclear and most indicators are that he was either working alone or had little to no organizational support from AQAP. Thus, the deadliest homegrown plot in the US during the period covered did not involve a returnee, but rather would better be conceived as a “lone wolf” or “single cell” attack.[21]

Seven of the 8 remaining deaths were caused by the first World Trade Center bombings in 1993. This plot was included because two of the six cell members were coded as homegrown under the operationalization explained earlier. These were Nidal A. Ayyad and Abdul Rahman Yasin and coding them as homegrown was marginal and relied on a judgment call. Ayyad moved to the US when he was 17—technically still a minor—and might have been excluded from being coded as “homegrown” had he not also attended Rutgers University and lived in the US for 8 years prior to the plot. Yasin, as explained earlier, was only included because he had been born in Indiana and therefore held a US passport. Despite his US citizenship, Yasin had been raised in Iraq. For purposes of this study, the first WTC plot was counted as having some homegrown participants. However, the same plot might rightfully be considered by others as a purely foreign plot carried out on US soil when one takes into account the specifics of Ayyad and Yasin’s relationship to the US.

Another marked difference between the first World Trade Center attack and that of the Fort Hood plot are the six core participants involved. Whereas the key to evading detection and disruption in Fort Hood may have been the lone-wolf character of the perpetrator behind a fairly unsophisticated attack, the success of the first WTC attack was in the organizational capacity of a larger group to put together bombs in a more sophisticated high-impact attack. I will return to this theme later.

The last victim of homegrown jihadi plots on US soil is that of Rabbi Meir Kahane at the hands of El Sayyid A. Nosair. According to McCann, the Egyptian born Nosair immigrated to the US in 1981, married a US citizen, and naturalized in 1989.[22] Nosair attended the mosque where Egyptian cleric Omar Abd al-Rahman preached. Rahman had deep links to the first WTC bombings and was himself convicted in the New York landmarks plot. This case is unique: Kahane, the founder of the Jewish Defense League, has himself been labeled a domestic terrorist by some because the group he founded has been linked to attacks against Soviet interests in the US. Kahane was also an elected member of the Israeli parliament, however his Kach movement was banned for being racist [23]. McCann also notes that it is likely that Nosair had at least some involvement with the first WTC bombings as documents found at his house were linked to the planning of the plot. Because those documents were in Arabic and left untranslated, it was not until years later that prosecutors realized the connection. Thus, the murder of Rabbi Meir Kahane might rightfully be considered an extension of the first World Trade Center plot. At the very least it can be concluded that some amount of organizational overlap existed between the two plots.

Conclusion and Discussion

While disaggregating homegrown jihadi plots in the US from the larger phenomenon using the JPW dataset leads to the problem of low sample size, looking at the individual plots and plotters seems to confirm what the numbers suggest: the presence of a returnee, at least in the case of homegrown jihadis in the US, decreases the likelihood that a plot will come to fruition. The presence of a returnee also decreases the likelihood that an executed plot will cause mass casualties. Of the five homegrown jihadi plots in the US in which at least one returnee was involved, only one of those came to fruition. That one plot, the case of Abdulhakim Muhammad, only killed a single individual. This stands in contrast to Hegghammer ‘s finding that, “the presence of foreign fighter returnees increases the effectiveness in attacks in the West,” [24] but is in line with the findings of de Roy van Zuijdewijn in the case of Europe.[25] These data suggest that plots in the US involving returnees are more prone to detection and therefore disruption.

If returnee participation lowers the likelihood of execution, what were the key factors leading to plot success? Of note is that not a single homegrown plot following the 9/11 attacks and through 2010 consisted of a cell size greater than one. In other words, every single homegrown jihadi plot in the time frame studied that was executed since 9/11 was done by a lone wolf or single cell actor. The vast majority of these executed plots had few, if any, victims who died. The bad news is that it seems that it is much more difficult for US intelligence agencies and law enforcement officials to interrupt homegrown jihadi plots where only one perpetrator is involved than when a larger network is involved. This is of concern because this is exactly what groups such as AQAP and ISIS have been encouraging.[26] Should would-be jihadis in the West begin to answer this call to lone-wolf jihadism encouraged by transnational terror organization, then domestic agencies tasked with counterterrorism will be faced with a difficult task.

Yet the good news is that these data suggest that counterterrorism measures taken against returnees and currently in place in the US are largely effective. The fact that they have traveled abroad to conflict zones may put them on the radar of intelligence and law enforcement. Some returnees may have no desire to commit acts of violence in their home countries in the West. Others may want to commit acts of terror in the US, but are unable to do so because they are under observation by those tasked with preventing terrorist plots. If going abroad really does increase their level of commitment to acts of violence at home, as suggested by Hegghammer [27], it is also makes it harder for them to carry out those attacks because it increases the likelihood of them being under observation by intelligence and law enforcement agents.

This article only looked at the case of homegrown jihadis in the US and the effects of veteran foreign fighters in plot execution over a specific period of time. It may very well be that the US is a special case and that the conclusions drawn here cannot be generalized to fit other Western countries. The rise of ISIS may pose problems not seen in earlier years. Perhaps the most glaring difference is the sheer numbers involved. By most estimations, the number of Western jihadis have skyrocketed to levels never seen before with estimates ranging between 3,000 and 5,000 Europeans fighting in Syria.[28] With limited resources, there may be a tipping point at which agencies tasked with countering terrorism on domestic soil are simply overwhelmed. If US agencies have so far been successful at preventing veteran returnees from executing plots, they may have done so within the historical context of few actual returnees to worry about. As hardened veterans from the Syrian conflict begin to come home, their numbers may reach a tipping point where keeping track of them becomes problematic. Whether or not we have reached that point is purely speculative. However, such a concern should be kept in mind as policy makers take into account future actions.

Another key difference of note is geography: Europe is geographically closer to the conflict zones than the United States. Would-be jihadis from the US must get on an airplane to reach conflict zones in Syria, North Africa, and Central Asia. Veteran returnees must also get on board an airplane to come back. While this does not pose an impossible barrier for veterans of Islamist conflicts, it is a substantial barrier nonetheless. The difficulty in leaving the US may be one factor in explaining why so few American jihadi sympathizers actually ever make it abroad to fight. Many such would-be foreign fighters are arrested before they ever make it to the airport. Simply buying the plane ticket or making other travel arrangements has been viewed as enough evidence of intent to join a terrorist organization to land the would-be foreign fighter in a federal prison. With European countries only recently beginning to bring criminal charges against would-be foreign fighters, it is too early to see if adopting what has long been the norm in the US will also yield similar results in Western Europe.

Proximity may also help explain why so few ever return to the US. Presumably, some proportion of such returnees would already be on a federal watch list making it difficult for them to get on board a plane to come home. Geography means returning to the Europe from the conflict in Syria requires none of the security checks now standard at most airports. Trains, buses, and ships which might transport veteran foreign fighters back to their country of origin are generally reported to have far fewer security checks than airlines. A recent example of this might be Ayoub el Kahzzani who is reported to have been known by authorities as a jihadi sympathizer and was on the French equivalent of the US terror watch list. The fact that he decided to attack passengers on a train from Amsterdam to Paris meant that he was not subject to the scrutiny that would have followed him had he taken an airplane. The same is probably true of the November, 2015 Paris attackers who killed 130 people and wounded many more. All seven of those directly involved in the attacks were citizens of EU countries and were either known by authorities as jihadi sympathizers or known to have traveled to Syria to fight with ISIS but were able to travel undetected and undeterred.

Another cautionary note is that proximity to Syria and North Africa also may mean an increase in the weapons available to veteran returnees. As LaFree from the University of Maryland has noted, the vast majority of successful terrorist attacks use guns.[29] Access to guns has generally not been a high hurdle for would-be domestic jihadists in the US. This is especially the case where the would-be terrorist is a US citizen and therefore entitled to gun ownership, but not so in Europe where restrictions on firearms are generally much tighter. The same routes which funnel jihadis back and forth from Europe to conflict zones like Syria could also be used to smuggle weapons to be used in domestic terror attacks in the West.

What is left to see is if the findings in these data can be confirmed. If my understanding is correct, then the original JPW dataset was compiled to look at the effects of foreign fighters on terrorist plots in the West and has been used to explain why jihadis tend to prefer to go abroad to fight rather than stay at home and attack local targets. The analysis conducted for this article is much more limited and narrow in scope: while using the same data set, it only asks whether or not those who returned from abroad were more dangerous than those who never left to become a foreign fighter. The evidence suggests that returnees are not nearly as effective or deadly as some other researchers have suggested. In order to do so, though, it was necessary to disaggregate data in such a way that each of those categories of interest was left with a very low sample size. Since the sample of homegrown veteran jihadi returnees in the US is so small, those comfortable with a more qualitative, thick narrative might find ample room to flesh out (or, indeed, falsify) some of the conclusions drawn here.

Another area for further study would be to use the same coding and disaggregation method used here and to apply it to other Western countries. This has been done in the case of Europe as a whole by de Roy van Zuijdewijn, [30] but further disaggregation could be done on a country-by- country basis. Are returnee effects greater or smaller in some European countries than in others? If so, could disparate policy approaches to the homegrown jihadi phenomenon explain any of that variation? As more and more European countries adopt US-like approaches to would-be jihadism – namely, arresting and prosecuting those wanting to go abroad to fight – the conclusion to these questions will only become more important.

About the Author: Christopher Wright is Assistant Professor of Public Management and Criminal Justice at Austin Peay State University where he teaches in that program’s Homeland Security concentration. He has a Ph.D. in Political Science from the University of Southern California. His research focuses on the intersection of transnational and domestic terrorism in the US, and the ways in which radical Islamists use the Internet and emerging technologies.


[1] See Hegghammer, Thomas. 2013. “Should I stay or Should I Go? Explaining Variation in Western Jihadists’ Choice between Domestic and Foreign Fighting.” American Political Science Review 107 (1): pp. 1–15.

[2] For instance: Sageman, Marc. 2010. “Confronting al-Qaeda: Understanding the Threat in Afghanistan.” Perspectives on Terrorism 2(4): pp. 4–25; Gartenstein-Ross, Daveed, and Laura Grossman. 2009. Homegrown Terrorism in the U.S. & UK. Washington, DC: Foundation for the Defense of Democracies.

[3] Byman, Daniel. 2015. “The Homecomings: What Happens When Arab Foreign Fighters in Iraq and Syria Return?” Studies in Conflict & Terrorism 38(8): pp. 581–602.

[4] Nilsson, Marco. 2015. “Foreign Fighters and the Radicalization of Local Jihad: Interview Evidence from Swedish Jihadists.” Studies in Conflict & Terrorism 38(5): pp. 343–358.

[5] Kenney, Michael. 2010. “’Dumb’ Yet Deadly: Local Knowledge and Poor Tradecraft Among Islamist Militants in Britain and Spain.” Studies in Conflict & Terrorism 33 (10): pp. 911–932.

[6] Vidino, Lorenzo. 2011. “Radicalization, Linkage, and Diversity: Current Trends in Terrorism in Europe,” pp. 1- 49. Santa Monica: RAND Corporation.

[7] Hegghammer, Thomas and Petter Nesser. 2015. “Assessing the Islamic State’s Commitment to Attacking the West.” Perspectives on Terrorism 9 (4): pp. 4–30.

[8] See: Bakker, Edwin and C. P. & E. Entenmann. 2013 Dealing with European Foreign Fighters in Syria: Governance Challenges and Legal Implications. The Hague: International Centre for Counter-Terrorism (ICCT); URL: http://www.icct.nl/download/file/ICCT-Bakker-Paulussen-Entenmann-Dealing-With-European-Foreign-Fighters-in-Syria.pdf ; Sinkkonen, Teemu. 2015 War on Two Fronts: The EU Perspective on the Foreign Terrorist Fighters of ISIL. Helsinki: Finnish Institute of International Affairs (FIIA); URL: http://www.fiia.fi/en/publication/470/war_on_two_fronts/ .

[9] Byman, Daniel. & Shapiro, Jeremy. 2014. “Be Afraid. Be Afraid a Little Afraid: The Threat of Terrorism from Western Foreign Fighters in Syria and Iraq” Foreign policy at Brookings; POLICY PAPER, Number 34, November

2014. Washington, D.C.: Brookings; URL: http://www.brookings.edu/~/media/research/files/papers/2014/11/


web.pdf .

[10] A press release to that effect can be found at URL: https://www.whitehouse.gov/the-press-office/2015/02/18/fact-sheet-white-house-summit-countering-violent-extremism .

[11] Davis, Sean. 2014. Responding to Foreign Terrorist Fighters: A Risk-Based Playbook for States and the International Community. Global Center on Cooperative Security. URL: http://www.globalcenter.org/wp-content/uploads/2014/11/Nov2014_Responding-to-FTFs_SD.pdf .

[12] De Roy van Zuijdewijn, Jeanine. 2014. “The Foreign Fighters’ Threat: What History Can (Not) Tell Us.” Perspectives on Terrorism 8(5): pp. 59 -73.

[13] Ibid, p. 65.

[14 Hegghammer (2013), p. 1 (see Supra at 1).

[15 The Jihadi Plots in the West dataset is available for download at URL: http://hegghammer.com/_files/JPW_Dataset_1.0.xls. The Foreign Fighters Observation Set can be downloaded at URL: http://hegghammer.com/_files/FF_Observation_Set_1.0.xls .

[16 De Roy van Zuijdewijn (2014) p. 62 (see supra at 12).

[17 On the one hand, it could be that the individual originally came to the US with positive attitudes (or, at least, ambivalence) towards their host country, and only later radicalized to the point where they believed violence against the US was justified. On the other hand, some individuals may have come to the US already predisposed to believing violence was justified, and thus could not be said to be “homegrown” in the sense that they became radicalized here. What event or change in attitude occurred where they went from passive believer in violent jihad to active participant is usually unknown, but one can easily see the difficulty in coding such individuals as homegrown vs. foreign.

[18] Those four were Hammad Samana (Torrance plot), Hysen Sherifi (North Carolina cluster), and Ibrahim El-Gabrowny and Fares Khallafalla (New York landmarks plot).

[19] Goetz, Kristina. 2010. “Muslim who shot soldier in Arkansas says he wanted to cause more death.” Knoxville News Sentinal, Nov. 13. URL: http://www.knoxnews.com/news/state/muslim-who-shot-solider-arkansas-says-he-wanted-ca .

[20] Blake, Mariah. 2013. “Internal Documents Reveal How the FBI Blew Fort Hood.” Mother Jones, Aug. 27. URL: http://www.motherjones.com/politics/2013/08/nidal-hasan-anwar-awlaki-emails-fbi-fort-hood .

[21] For a more complete discussion, see: Simon, Jeffrey D. 2013. Lone Wolf Terrorism: Understanding the Growing Threat. Amherst, New York. Prometheus Books.

[22] SMcCann, Joseph T. 2006. Terrorism on American Soil. Boulder, CO. Sentient Publications, pp. 170–176.

[23 Ibid.

[24] Hegghammer (2013), pg. 11 (see supra at 1).

[25] de Roy van Zuijdewijn (2014) (see supra at 12).

[26] Hegghammer and Nesser (2015) (see supra at 7)

[27] Hegghammer (2013) (see supra at 1).

[28] Schmid, Alex and Judith Tinnes. 2015. Foreign (Terrorist) Fighters with IS: A European Perspective. The Hague. International Centre for Counter-Terrorism. URL: http://icct.nl/wp-content/uploads/2015/12/ICCT-Schmid-Foreign-Terrorist-Fighters-with-IS-A-European-Perspective-December2015.pdf . If the upper estimate of 5,000 Europeans fighting for ISIS is correct, then the authors note that this means that 20% of ISIS fighters are probably European in origin.

[29] LaFree, Gary. 2011. “Using Open Source Data to Counter Common Myths About Terrorism”. In: Criminologists on Terrorism and Homeland Security, Brian Forst, Jack Greene and Jim Lynch (Eds). Cambridge: Cambridge University Press

[30] De Roy van Zuijdewijn (2014) (supra at 12).

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