Lessons from September 11 about the post-conflict threat posed by foreign terrorist fighters

ABSTRACT

As the Islamic State’s hold on territory was gradually diminished in Iraq and Syria, countries around the world expressed concern that the group’s large contingent of foreign terrorist fighters (FTFs) would return to their home countries to continue their campaign of violence. However, as time has passed and relatively few attacks have taken place, some wonder if the threat has passed. This article argues that an FTF returning directly to their country to commit an act of violence is only one way that such a threat may manifest itself, but that there are other ways that may ultimately take longer to appear. This article utilises the network of individuals responsible for carrying out the 11 September 2001 terrorist attacks as a case study to demonstrate the various pathways and timeframes through which FTFs may pose a future threat. This approach reveals that, although the concern of FTFs directly returning to participate in attacks is valid, the varied and long-term ways in which FTFs may ultimately pose a threat are of equal if not greater concern.

KEYWORDS:

• Terrorism
• foreign terrorist fighters
• September 11
• counterterrorism

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 It is worth noting that this particular case does not fit into the narrative of FTFs posing the greatest threat to their countries of origin, as Nemmouche was actually from Belgium, not France.

2 One exception, on a smaller scale, is the work of Holman (2015), which finds that foreign fighting networks and domestic attacks networks in Belgium and France seemed to be separate from each other, leading to the conclusion that Hegghammer’s work potentially overestimates the threat of returning FTFs. Other studies mentioned the problem of returning fighters as a possible threat either broadly or in the context of a specific country, but did not explore the threat in any systematic detail (Cilluffo, Cozzens, & Ranstorp, 2010; Zammit, 2015).

3 Two other studies provided some analysis of the threat posed by returning FTFs, but did so as part of a broaderfocus on plots and attacks in Western countries. Consequently, the importance of their findings for the debate on the threat posed by returning FTFs was not the main focus and received less discussion than offered on the subject by Hegghammer (Sageman, 2009; Cruickshank, 2011). Additionally, these pieces do not always distinguish between individuals who travelled abroad for training and those who actually fought while abroad.

4 Hegghammer (2013, p. 10) is very careful to point out that this percentage should not necessarily be treated as a hard and fast number because of data limitations, including the possibility of underreporting of the overall number of FTFs, which would make the percentage even lower.

5 It is important to note that at least one scholar pushes back on Hegghammer’s findings, using a modified version of the Hegghammer dataset to demonstrate that FTFs do not make plots more likely to succeed or more violent (Leduc, 2016).

6 In previous versions of this article, there was an additional category for associates of the hijackers. This category was based on Krebs' (2002) work on the September 11 network. However, additional research by the author led to several doubts about the actual connectedness of those individuals to the September 11 network, particularly given the requirement in this article that individuals included in the dataset would only be included based on evidence of active support.

7 This later qualification describes the experience of someone like Hani Hanjour. He travelled to Afghanistan to fight in 1989, only to find that the Soviets had left. He instead worked for a relief agency (National Commission on Terrorist Attacks upon the United States, 2004).

8 An important caveat to this discussion is that the data collected here is not social network data. It does not tell us anything about the importance or centrality of particular individuals. It is possible that, even though the logistics individuals in the September 11 plot generally had less foreign fighting experience than operatives or leadership figures, the logistics individuals who did have such experience were particularly critical to the plot. Unfortunately, the data here does not allow us to evaluate that possibility.

9 Because precise information about exactly when an individual arrived on the battlefield as an FTF is hard to come by, the calculation here is made based on the year of arrival. So, an individual arriving in Afghanistan in 1991 would have been calculated as having 20 years of time from the moment he arrived until the September 11 attacks, which were carried out in 2001.

10 The author would like to thank one of the anonymous reviewers for their helpful advice in more clearly discussing this particular pathway.

11 It is important to point out that Vidino (2007) notes that the role of a recruiter might be diminishing when it comes to certain networks, to the point where local cells may form and function in the absence of a recruiter.