Cheese Bells and Foreign Fighting

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Editor’s Note: This is an excerpt from “Book Review Roundtable: Foreign Fighters in the Armies of Jihad” from our sister publication, the Texas National Security Review. Be sure to check out the full roundtable.

Daniel Byman, Road Warriors: Foreign Fighters in the Armies of Jihad (New York: Oxford University Press, 2019).


Few topics in international security have captured as much attention in recent years as that of foreign fighters. A Google search for the term now yields over a million hits, while Google Scholar suggests it features in some 20,000 publications, three-quarters of which are from the 2010s. Interest among policymakers has been similarly high: Since around 2013, many countries around the world have implemented measures to combat foreign fighting, and in 2014 the phenomenon even got its own U.N. Security Council Resolution.

The reason for the surge in attention was, of course, the departure of unprecedented numbers of Islamist volunteers to fight in Syria’s civil war between 2012 and 2016. In this period, tens of thousands of Muslims from all over the world, including over 5,000 from Europe, joined the Syrian rebellion. A large proportion of them ended up joining the Islamic State of Iraq and the Levant (ISIL), the world’s most formidable terrorist organization at the time, prompting fears that they would not only fuel the ranks of jihadism in the Middle East, but also pose a global terrorist threat.



For the same reason, the academic literature on foreign fighters is heavily centered on the case of Syria in the 2010s, which has been studied in depth from several angles. An important line of inquiry has been the individual-level characteristics and recruitment pathways of the fighters. Another has been the in-theater activities of the fighters and their impact on their host organization and the Syrian conflict. Yet another has been the prospect of so-called blowback or spillover from travelers to Syria in the form of international terrorist attacks. To be sure, the literature has not been exclusively focused on ISIL volunteers. In fact, a byproduct of the increased general interest in foreign fighting has been studies into little-known variants of the phenomenon, such as far-right, Shiite, or anti-ISIL foreign fighting. Still, the Syrian jihadi case looms larger, to the point where, in the public consciousness, the term foreign fighter has become closely associated with ISIL volunteers.

Enter Daniel Byman’s new book Road Warriors, which takes a long historical view on the phenomenon of Islamist foreign fighters. The book shows with great clarity that foreign fighters who went to Syria in the 2010s are but the latest in a long series of jihadi foreign fighter mobilizations and that the phenomenon needs to be understood — and dealt with — as the decades-old and wide-ranging phenomenon that it is. Byman’s account starts in 1980s Afghanistan and passes through early-1990s Bosnia, mid-1990s Chechnya, late-1990s Afghanistan, mid-2000s Iraq, and late-2000s Somalia before reaching the Syrian civil war. He then looks at the repercussions of jihadi foreign fighting in Europe and the United States before ending with an in-depth reflection on what can be done to counter the phenomenon.

Road Warriors is an extremely valuable addition to the literature. It is the first long history of jihadi foreign fighting and, as such, it allows us to see patterns and nuances that are less apparent. It is also highly accessible, making it very well suited as an introduction to the topic for newcomers. Byman’s clear prose and his organization of the book into chronological chapters centered on key individuals constitute a breath of fresh air in a sometimes dense academic literature. At the same time, the book is packed with details and insights that even jihadism specialists will learn from.

Of particular value is the chapter on countermeasures, in which Byman presents an innovative framework for thinking about the constituent parts of the foreign fighter challenge and offers policy suggestions that are as specific as they are original. In books with such breadth of scope, there will always be minor quibbles to be had about details of specific cases (I had a few for 1980s Afghanistan) and about editorial decisions (I would have liked, for example, to see a nod to pre-1980s cases, such as the 1948 Palestine war or the late 1960s Islamist Fedayin). None of this, however, detracts from the fact that Road Warriors is a highly accurate synthesis of a complex literature and is a major academic achievement. 

Three Features of Jihadi Foreign Fighting

The story told in Road Warriors brings out three important macro-features of jihadi foreign fighting that merit highlighting. The first is continuity. The book shows that all the main foreign fighter contingents are connected, not just in the sense that they represent the same type of activity, but in the sense that we find some of the same people in several different conflict zones. Abu Abdel Aziz Barbaros in Bosnia had also fought in Afghanistan, Ibn Khattab in Chechnya had fought both in Afghanistan and in Tajikistan, and Abu Musab al Zarqawi in Iraq had previously fought in Afghanistan in both the 1980s and 1990s. Some of the men who went and fought in the Syria civil war, such as Abu Firas al Suri, had resumés going back to the 1980s. In my recent book The Caravan, I mention the case of Abd al Aziz Ali, an Egyptian in the 1980s Afghan jihad who also fought in Palestine in 1948. This continuity is in addition to the considerable ideological continuity across contingents  — exemplified by the influence of Abdullah Azzam’s writings on post-1980s foreign fighters — as well as the shared sense of history, evident from the way foreign fighters in Iraq and Syria emulate and celebrate famous predecessors from the 1990s, such as Ibn Khattab. This is important, as it shows that we are not dealing with disparate phenomena that happen to resemble each other but rather with one and the same movement. Moreover, it suggests that the movement’s existence is not dependent on the features of any one of the host conflicts. To be sure, the size of the various contingents varies by conflict-specific factors — for example, the Syrian war attracted large numbers in part because the rebels initially enjoyed widespread international support — but the movement as a whole transcends individual conflicts. It follows that the phenomenon will likely not disappear with the end of the foreign fighting in Syria. It is likely to reemerge in any new conflict zone that will allow it.

The second insight is the centrality of foreign fighting to jihadism. Byman’s account makes it clear that the history of jihadism is largely the history of jihadi foreign fighting. Road Warriors provides a better overview of the jihadi movement’s history than any book about jihadi international terrorist operations. As important as it is to know the history of the latter, foreign fighting is the rule and international terrorism is the exception as far as the jihadi movement is concerned. The foreign fighter contingents presented in Road Warriors involved an order of magnitude more people than have ever taken part in jihadi terrorist attacks outside conflict zones. Jihadi foreign fighters have also undertaken many more operations and killed more people than have their out-of-theater comrades.

Moreover, the movement’s biggest heroes — Azzam, Ibn Khattab, al Zarqawi — are all people who primarily waged asymmetrical warfare in conflict zones. The main exception is Osama bin Laden, but even he had solid foreign fighter credentials before orchestrating the 9/11 attacks. By contrast, those who executed major out-of-theater attacks, such as Muhammad al Islambouli (1981 Sadat assassination), Muhammad Atta (9/11), or Abdelhamid Abaaoud (2015 Paris attacks) are not treated with nearly the same reverence. This is not to say that the out-of-theater activities of jihadi groups are insignificant. They are important to international politics, because they have an outsize psychological impact that can make countries go to war (America post-9/11), devastate tourism industries (Egypt after the 1998 Luxor attacks), or trigger extreme anti-Muslim policies (China after the Uyghur stabbings in the late 2000s). It is only to say that the jihadi movement depended for its survival on access to conflict zones and foreign fighting seems to be its lifeblood.

The third and related insight is that jihadis have been more successful as foreign fighters than as domestic revolutionaries. All the chapters in Road Warriors take place in wars that jihadis themselves did not start, and several protagonists had a history as failed revolutionaries. In fact, all Sunni Islamist attempts to topple the local government or start an insurgency in a country at peace have failed. In Egypt, militant Islamists periodically made such offensives from the 1950s to the early 1990s, each time without success. In Syria, the uprising of the late 1970s was brutally repressed. In Algeria in the 1990s, the militants held out for slightly longer, but eventually suffered the same fate. Ditto for the al-Qaeda offshoot that tried to wage a terrorism campaign in Saudi Arabia in the early 2000s. It is only in areas that have descended into war for other reasons — 1980s Afghanistan, 2000s Iraq, or 2010s Syria — that jihadis have truly thrived. This testifies to the limited popular appeal of jihadism, to the difficulty of mounting revolutions, and to the repressive power of modern technocratic nation-states.

Escaping the Cheese Bell

These three observations buttress a hypothesis about the relationship between foreign fighting and terrorism that I have alluded to in previous writings but not yet articulated in full. I call it the Cheese Bell Theory of foreign fighting. It suggests that modern states have become so effective at repressing small rebel groups that the latter only survive if they can periodically leave the area of state control. Foreign fighting is a mechanism for achieving this. Functioning states are like cheese bells in the sense that they crush all minor forms of rebellion inside their jurisdiction. Rebel groups that are caught inside the bell tend to get dismantled, while those that can leave — for example by coming and going as foreign fighters — stand a better chance of survival.

It is useful here to reflect on just how powerful the modern technocratic state has become. Taxation and the legal system allow the state to operate powerful police forces and intelligence services, giving the state an enormous operational advantage vis-à-vis small rebel groups. Technological advancement increases this advantage in the long term, because states have more resources at their disposal and can harness new technology more effectively than can small non-state actors. Moreover, digital technology makes societies more regulated and increases the observability and traceability of economic transactions, interpersonal communications, and individual physical movements. In wealthy modern societies, almost everything we do is recorded and potentially accessible to a capable intelligence service: our purchases (through credit card records); our movements (through surveillance cameras); and of course our phone calls, emails, and internet activity. Even if you try to stick to analogue technologies, such as cash and personal meetings, you can get caught on other people’s mobile cameras, and artificial intelligence may even flag you for not leading a normal, trace-leaving digital life.

Much has been written about the advantages that new technologies confer on terrorist groups and about the opportunities that our increasingly connected societies offer to malicious actors. However, a strong argument can be made that these advantages are primarily of a tactical and not strategic nature. In functioning states, new technologies appear to make it easier to carry out single operations, but harder to wage sustained campaigns of violence. If you are a first-time terrorist who is not on the radar of the authorities, you can plan in relative peace and make full use of the opportunities of modern technology. After that first attack, however, the security services come after you, and then it becomes a whole different ballgame — one that modern states, especially the wealthy ones, almost always win.

This argument is supported by two broad patterns in the history of terrorism in the West. The first is that the long trend of terrorist activity — measured in both attacks and casualties — has been steadily declining since the late 1980s. The break in the curve is usually attributed to the end of the Cold War, but the late 1980s also marks the beginning of the systematic introduction of information technology in Western state bureaucracies and the widespread societal adoption of digital communications technologies. It is not far-fetched to suggest that terrorism in the West may have declined not only because of the end of the Cold War, but also because the computer, in the broad sense, has empowered intelligence services more than it has terrorist organizations. The second pattern is the virtual disappearance of active terrorist organizations from Western societies. In the 1970s and 1980s, much terrorism was carried out by organizations and these organizations sometimes survived for years, carrying out numerous attacks before being dismantled by police. In the 2000s and 2010s, terrorism — at least the large-scale variety — is perpetrated, to a much larger extent, by cells and individuals as opposed to stable organizations. Running a classical rebel organization — with a leadership, an internal bureaucracy, and some continuity of personnel — has become extremely difficult in Europe and North America. To be sure, violent political organizations still exist, but these are usually organizations that engage in low-level violence and therefore do not attract the full wrath of the modern surveillance state. Groups that perpetrate mass-casualty attacks, on the other hand, tend to get dismantled relatively quickly.

To both of these patterns there is a partial exception, namely jihadi terrorism. While the terrorist activity curve in the West from 1990 to 2020 is generally downhill-pointing, there were temporary surges in activity in the 2000s and 2010s, especially when measured in casualties. Much of this activity was perpetrated by militant Islamists, despite the fact that Western security agencies put most of their counter-terrorism resources into fighting jihadis. The latter thus seemed to defy the forces of repression that were pushing far-right, far-left, and ethnic separatist violence down. Moreover, although jihadis have not been able to run stable organizations inside the West, they have periodically been able to sustain logistical structures there that come close to those of classical organizations. How can we explain this exception? Why has jihadism been so lethal and resilient in the West when other ideological movements have struggled, and when jihadism recruits from a much smaller population (Muslims in the West)?

The Cheese Bell Theory suggests that the answer lies in foreign fighting. For a variety of reasons, jihadis in the West have been willing and able to engage in a lot more foreign fighting than have radicals of other ideological orientations. This has enabled members of jihadi networks to temporarily escape, at least partially, the watchful eye of their countries’ intelligence services, while getting training and forming connections with more experienced militants in conflict zones. This has provided jihadis with what military theorists call “strategic depth,” namely, a distance between the front lines and the home base so large that the enemy cannot reach the rebels’ home base and disturb force production. For example, when foreign fighters are off in faraway places, such as Afghanistan or Syria, it is much harder for European security services to disrupt their training and plotting than if the same activity were taking place in France or Germany. In short, foreign fighting has allowed jihadis to escape the cheese bell.

Meanwhile, most other militant movements in the West — be they the far right, the far left, or radical separatists — have generally not had the same privilege, at least in the past few decades (the Cold War provided more such opportunities for those other group types). There have been exceptions, such as the neo-Nazi foreign fighters in the Ukraine, or the leftist ones fighting with the Kurds against the Islamic State in the mid-2010s, but these activities have not been nearly as long-lived or involved as many people as the foreign fighting of the jihadis. As a result, non-jihadi militants in the West have been stuck inside the cheese bell, living at the mercy of their ever more capable security services.

Similar dynamics have likely also been at play in the Muslim world, although the tools and techniques of state repression have been somewhat different. Until recently, at least, authoritarian regimes have generally relied on more heavy-handed methods and more bulk surveillance of political opponents than have democratic states, but the end result has been the same: a considerable ability to repress and dismantle small rebel groups on their own territory. As a result, jihadi groups operating in Muslim countries at peace have tended to get dismantled relatively quickly, as noted earlier. This tendency is likely to strengthen in the years ahead as non-democratic regimes get access to more advanced surveillance technology while remaining legally unrestrained in the deployment of these technologies.


For jihadis, then, foreign fighting has been more than an ideologically meaningful modus operandi or a series of military adventures. It has been an activity of utmost strategic importance, one that has been crucial to the very survival of the jihadi movement. It is not the only source of the movement’s resilience, but it is arguably one of the principal ones, along with propaganda distribution technologies and the persistence of armed conflicts in the Muslim world. Foreign fighting has been a mechanism for avoiding domestic state repression, and its value for rebels has increased in recent decades as the repressive power of modern technocratic states has grown.

It follows from the Cheese Bell Theory that the jihadi movement will suffer if its opportunities to engage in foreign fighting are reduced in the future. It is probably impossible to completely eliminate jihadi foreign fighting, but it is certainly possible to do more than governments did from the 1980s to the mid-2010s. As Byman notes, countering foreign fighting was generally not a priority in either the West or in the Muslim world prior to the Syrian civil war. In recent years, many countermeasures have been put in place, and Byman offers further suggestions on what to do. Jihadi strategists thus have every reason to be unhappy with the publication of Road Warriors.



Thomas Hegghammer is a senior research Fellow at the Norwegian Defence Research Establishment (FFI) in Oslo and the author of The Caravan: Abdallah Azzam and the Rise of Global Jihad (Cambridge, 2020).

Image: Flickr (Photo by Freedom House)