#title The Radical Milieu
#subtitle Conceptualizing the supportive social environment of terrorist groups
#author Stefan Malthaner and Peter Waldmann
#date 16 Sep 2014
#lang en
#pubdate 2026-05-27T23:36:25
#authors Stefan Malthaner, Peter Waldmann
#topics terrrosim,
#publisher Routledge
#source Studies in Conflict & Terrorism. <[[http://dx.doi.org/10.1080/1057610X.2014.962441][dx.doi.org]]><br>**Author correspondence:** Stefan Malthaner, European University Institute (EUI), Via dei Roccettini 9, I-50014 San Domenico di Fiesole (FI), Italy. E-mail: Stefan.Malthaner@EUI.eu

<em>Abstract: Terrorist groups are not completely isolated, socially “free-floating” entities, but emerge from and operate within a specific, immediate social environment – what we call the radical milieu – which shares their perspective and objectives, approves of certain forms of violence, and (at least to a certain extent) supports the violent group morally and logistically. In this article we introduce an approach to conceptualize and analyse this formative and supportive social environment of clandestine groups, addressing the questions of how the radical milieu emerges, what forms it takes, and what role it plays in shaping the development of violent groups. Our focus, thereby, rests on relationship-patterns between violent groups and radical milieus as well as on processes of interaction between radical milieus and their broader political and societal environment, which may entail dynamics of support and control but also isolation and radicalization.</em>

<br>Terrorism is a strategy of violent attacks designed to spread fear and attract attention that is typically adopted by relatively small underground-groups.[1] They often emerge in the context of social movements or religious or ethnic communities, but within these movements they generally represent a rather marginal phenomenon and their clandestine form of operation separates them from their social environment. Nevertheless, terrorist groups should not be regarded as completely isolated, socially “free-floating” entities. Radicalization and terrorist violence[2] are the result of political and social processes which involve a broader set of actors and social groups and cannot be understood in isolation. Not only do they develop in the context of escalating interactions between social movements, political opponents, and state actors. Terrorist groups also emerge from and operate within a specific, more immediate social environment – which we call the <em>radical milieu</em> – which shares their perspective and objectives, approves of certain forms of violence, and (at least to a certain extent) supports the violent group morally and logistically.

In this article we introduce an approach to conceptualize and analyse this formative and supportive social environment of clandestine groups, addressing the question how the radical milieu emerges, what forms it takes, and what role it plays in shaping the development of violent groups. Our focus, thereby, rests on relationship-patterns between violent groups and radical milieus as well as on processes of interaction between radical milieus and their broader political and societal environment, particularly state authorities and political opponents.

The relationship between terrorist groups and their immediate social environment represents an under-researched field.[3] The past fifteen years saw an immense increase in the number of publications on “terrorism”. But whereas this literature has examined, for example, conditions and factors shaping individual processes of radicalization, organizational forms of terrorist groups, and the socio-structural “root-causes” of terrorism in great detail, there are few studies on the immediate, supportive environment of violent groups.[4] One reason for this might be the common belief that terrorism as a strategy of clandestine groups would (in contrast to guerrilla warfare) not depend on any broader social support. Yet, on closer observation it becomes clear that this environment is of crucial importance in processes of political violence as it shapes individual pathways of radicalization and influences the development of violent groups. Thereby, the role of the radical milieu must not be reduced to that of a presumed “hotbed of radicalization”. Nor is our intention to draw attention to the radical milieu as a supportive environment that has to be undermined by state-security services in their efforts to counter terrorist violence. The importance of the radical milieu for understanding processes of political violence lies in the complex and often ambivalent relationship between clandestine groups and their immediate social environment, which influences the makeup and tactical choices of the armed groups and can have escalating but also violence-constraining and de-escalating effects. And it is precisely via their effects on the radical milieu that repressive measures by stateauthorities often fuel radicalization processes and contribute to dynamics of violent escalation rather than controlling them.

In the following, we introduce this approach by, firstly, embedding it within the literature and discussing the main lines of research on which it builds. The following sections then present the concept of “radical milieu” in more detail, discussing also related concepts such as “reference groups” and identify various processes in which these environments can emerge. After examining different forms and characteristics of radical milieus, we then turn to a more detailed analysis of, firstly, relations between radical milieus and their wider social and political environment and, secondly relations between terrorist groups and radical milieus, specifying and illustrating relational mechanisms of influence and constraint as well as radicalization and isolation. In the last section we summarize the potential benefits of this approach for further developing a relational approach to the analysis of processes of political violence.

*** 1. Terrorist groups and their social environment in the research-literature

It is no coincidence that the social context from which terrorist groups emerge and in which they operate has not been addressed by many studies on political violence. Whereas data on perpetrators can be obtained from court-documents or media-reports, and surveys offer insights into attitudes towards terrorism among the broader population, access to the more immediate social environment of clandestine groups is difficult, not least because of strong suspicions towards outsiders. These suspicions are, in fact, often not unwarranted as groups allegedly linked to terrorist groups – such as political parties, legal-aid groups, militant youth groups connected to the radical fringe of a movement, etcetera – are regularly the target of surveillance and repressive measures by state security services. Thus, and in particular since the emergence of so-called “home-grown” Islamist terrorism in Europe, the literature on political violence has tended to focus on individual pathways of radicalization or structural preconditions. More generally, the field has been criticized, particularly by proponents of the school of <em>Critical Terrorism Studies</em>, for de-contextualizing its object of study and isolating it from its social and political environment, neglecting the role of state repression in processes of violent escalation, and promoting an understanding of political violence as an essentially pathological phenomenon.[5] Yet, this critique seems only partially justified. It fails to acknowledge that terrorist violence has been for many years also the subject of comparative sociological research that explicitly emphasized historic and political contextualization.[6] Moreover, a number of studies among the “mainstream” of terrorism studies have contributed rich empirical analyses of radicalization and political violence that consider important aspects of social context.[7] Overall, recent years have seen a change in perspective in research on political violence towards an emphasis on contextualisation and on the processual and relational quality of phenomena of political violence.[8]

The approach developed here builds in particular on three lines of research: works from (or adopting approaches from) social movement studies that trace the emergence of clandestine groups in the context of broader protest movements; studies that examine relations between terrorist groups and their wider social environment; and research on individual pathways of radicalization that consider aspects of social context.

Research on protest-movements and left-wing violence in Europe, in particular, has from early on emphasized the fact that the emergence of violent groups is embedded within larger political conflicts and closely linked to their social environment. Works on the German Red Army Faction and the Italian Brigate Rosse, for example, traced the emergence of violent groups in the context of militant currents and subcultures within the broader movements, in a process shaped by confrontations with the police and political opponents.[9] Quite similar processes can be observed in the development of Islamist movements, for example in Algeria and Egypt.[10] Thereby, as a number of recent studies show, militant groups not only radicalize in confrontation with opponents, but also as a result of mechanisms of “political outbidding” with other (militant or non-militant) groups within the same movement, with whom they compete over media attention and support among followers.[11] The decision to move underground, then, fundamentally transforms the relationship between armed groups and their social environment. It entails the need to restrict or cut off personal contacts with the broader social movement milieu, often accompanied by conflictive processes of self-separation and a dynamic of isolation and radicalization of clandestine groups.[12] Even if these studies discuss the immediate social environment from which violent groups emerge, such as militant subcultures, only in the margins, they nevertheless have laid the groundwork for the approach developed here. They make clear that the step to move underground and to adopt terrorist strategies takes place in the context of broader processes of political mobilization and as a result of shared experiences of violent clashes and police-persecution, and often on the background of widespread acceptance of militant forms of action among certain groups within the movement, even if clandestine strategies then entail a separation from this environment.

Works on the logic of terrorism as a strategy of political violence[13] have, in addition, identified a number of important features of the relationship between violent groups and their social and political environment. This includes a specific duality of dependence and distance towards this environment. Terrorism as a strategy of clandestine political violence is typically chosen by groups that do not command sufficient public support (and do not have sufficient military resources) to challenge a government openly and directly. Instead, they rely on a campaign of violent attacks that is designed, on the one hand, to spread fear among opponents, to force them into concessions, or provoke them to overreact, and, on the other hand, to mobilize a wider following among the population. Still, violent groups depend on a certain extent of logistic support from a more immediate circle of supporters, with whom they remain connected more or less closely. And they rely on moral and political support to sustain their self-concepts as fighter-heroes. Completely isolated groups may be able to survive for some time by obtaining financial resources by robbing banks, for example. But without shelter, supplies, or assistance provided by supporters and – most crucially – constraints on collaboration with and informing to the police enforced via norms of loyalty and non-betrayal within milieus surrounding clandestine groups, the latter will not be able to sustain a violent campaign in the face of persecution by security services over prolonged periods of time.[14] Moreover, the need to recruit new members intertwines terrorist groups with a wider circle of legal or “above-ground” supporters.[15] Moral and political support is often equally important for militant activists to be able to sustain the hardships of clandestine struggle and their self-concept as fighter heroes. As Crenshaw emphasizes, most violent activists “need to feel virtuous”,[16] and one of the most important mechanisms to sustain and reinforce notions of righteous struggle is the respect and recognition received in interaction with the militants’ immediate social environment. Yet, even if these mechanisms were repeatedly mentioned in the literature, they were rarely made the subject of a focused empirical study. Among the few works that provide deeper insights into these relationships are, for example, the ethnographic studies by Burton and Sluka on neighbourhoods in Belfast and Zuleika’s work on the Basque country, which offer valuable insights into the ways in which the militant groups were embedded within and relied on support from parts of the population.[17]

A third line of research that illustrates the importance of the social environment of terrorist groups includes works on individual pathways of radicalization and joining clandestine groups. One of the most established findings in research on social movements as well as studies on political violence, thereby, is that the process of joining a militant group is often initiated by personal relations such as acquaintances, friendship-groups, or family-ties; that is, via personal networks which link violent groups to their social environment. Research on the Red Brigades and the Red Army Faction,[18] as well as studies on the PIRA,[19] ETA,[20] and Islamist groups in the Middle East and Europe[21] have shown that the majority of militants had pre-existing social ties to the milieu around the violent group, which were instrumental in initiating and shaping their pathways towards militant activism. Moreover, radicalization often takes place in friendship groups and cliques, which together join radical milieus and later clandestine groups. Future militants are socialized in these contexts and adopt perspectives and frames of interpretation, which is why Della Porta calls these subcultures from which militant activists emerge “micromobilization-contexts”.[22] Individual pathways of radicalization, thus, take place in the spatial and social environment of radical milieus. Neumann, for example, in his studies on militant Islamist groups in Europe, emphasizes the role of what he calls <em>recruitment grounds</em> in trajectories of individual activists, which includes meeting-places such as mosques, certain youth-centres, or Islamist book-shops, but also places where young men are particularly vulnerable to ideological outreach and recruitment-efforts of Islamist activists, such as prisons or refugee centres.[23] Yet, in most studies on individual processes of radicalization the social environment remains a mere contextual variable and the reference to the radical milieu superficial. One exception is Quintan Wiktorowicz’s study on an Islamist milieu in Great Britain, which carefully reconstructs the outlines of an emerging radical milieu in the context of which various violent groups formed.[24] Similarly, research done by Lene Kühle and Lasse Lindekilde on the radicalization of young Muslims in Aarhus explicitly considers the religious milieu in which these processes were embedded.[25]

*** 2. The concept of radical milieu and related terms

By introducing the concept of <em>radical milieu</em> we seek to draw attention to relationship-patterns and dynamics of interaction between terrorist groups and their social environment.[26] We understand the term to denote the immediate social environment from which violent groups emerge and to which they remain socially and symbolically connected. They share experiences, symbols, narratives, and frameworks of interpretation with this milieu and the armed groups are – at least to a certain extent – linked to (or part of) its social networks. <em>Milieu</em> is used her in the sense of a social formation, a relational entity consisting of individuals who interact and develop common perspectives and notions of collective identity. Our understanding of the concept leans on the original meaning of the term in Hippolyte Taine’s milieu-theory (and the way Emile Durkheim’s used the concept in his work) insofar as it denotes a social environment of formative character in relation to an actor.[27] Far from being static or passive “context”, the radical milieu, as we understand the concept, represents a dynamic and evolving relational field which includes groups and individuals which pursue their own interests, interacting and to some extent collaborating with, but at times also criticizing, challenging, or even confronting the militant activists. Only if the radical milieu is conceived in this sense as comprising an array of “actors” (however diverse and incoherent) are we able to speak of relationships and interactions between armed groups and this social environment; instead of an understanding of milieu as amorphous social context which would influence the terrorist groups merely as an abstract idea or perception rather than in concrete interactions.

<em>Radical[28]</em> is conceived here to denote forms of action, frameworks of orientation, and attitudes that define a political conflict in absolute terms, that are characterized by a high degree of commitment to one’s own side, and which include the approval or use of violence. We thus put violence at the centre of our understanding of the radical milieu, arguing that it is its constitutive and defining feature: radical milieus emerge in the context of militant confrontations, often as a result of direct or indirect experiences of violence (by the police or political opponents), which is at the same time accompanied by the approval and adoption of militant practices within wider parts of radical milieus. Thus, our concept of <em>radical milieu</em> does not refer to abstract beliefs but to experiences, militant practices, as well as to relationships, in particular relationships with violent actors.

The perspective proposed here analytically distinguishes – and thus allows to analyse – three social ”circles” (actors and environments) and corresponding relationships between them: (1) Terrorist groups, which are set in relation to (2) the radical milieu as their immediate, supportive environment, which are, in turn, distinguished from (3) their broader social and political environment, including state authorities and political opponents as well as the broader social movements or ethnic/religious communities from which they emerge. Thereby, the acceptance or use of certain forms of violence marks the boundaries between them. Terrorist groups are characterized by the fact that they use extreme forms of violence to challenge the state (or political opponents), which they can only do by operating underground to evade persecution. The radical milieu, in contrast, is characterized by more open structures (spaces, organizational structures, media and communication) and its members limit their activities to more or less militant forms of protest. Even if semi-clandestine groups and lower-level forms of violent tactics (arson attacks, violence in street battles) can be found within radical milieus, as for example among the various militant groups within the radical fringe of the “Haschrebellenszene“ in Berlin in the early 1970s or the nationalist Basque youth organization <em>Jarrai</em>, they remain at a level clearly distinct from terrorist violence – with respect to the step to fully move underground as well as with respect to the forms of violence used. The wider social environment beyond the radical milieu, in turn, is characterized by highly ambivalent attitudes towards violence or the open rejection of violence and more militant forms of protest.

These social environments are, of course, not to be understood as static or homogeneous social entities, but as dynamic relational structures surrounding terrorist groups which evolve over the course of processes of political violence. It is also important to note that radical milieus can take various forms, differing significantly in size, social composition, as well as with respect to how stable or fluid they are (see section 4. below). Yet, while boundaries differ in the degree to which they are more clear-cut or fluent and permeable, the different experiences of, attitudes towards, and participation in forms of political violence do, in fact, mark important separating lines also in the perception of the individuals involved.

To further specify the concept it is useful to distinguish it from related terms, such as the concept of <em>reference-group</em>. The latter concept refers to the symbolic and communicative dimension of terrorist violence and the way violent groups orient themselves towards and address real and imagined groups and audiences.[29] Radical milieus, in contrast, are linked to clandestine groups by patterns of actual social relationships and face-to-face interaction. Radical milieus and reference groups can partly overlap, but may also diverge significantly. Communications and messages of armed groups are, of course, also directed at their immediate supportive milieu, which represents an important audience. As a result of estrangement from the wider movements and other audiences, the radical milieu may even become the militants’ main reference group. Yet, typically the immediate supportive environment only represents a minor part of the audiences that terrorist groups seek to address. Moreover, the groups which militant activists refer to and address may also include abstract categories such as the proletariat, the worldwide community of believers, or oppressed people in other parts of the world, for whom and in whose name they claim to fight.[30] Another related concept is that of <em>constituencies</em>.[31] While constituencies also denote a “real” social group to which militant groups set themselves in relation, the term usually refers to the wider communities which the militants claim to represent, rather than their immediate supportive environment.

*** 3. Processes of formation

With respect to the formation of radical milieus, three basic processes can be distinguished which differ with respect to the basic relation between the terrorist groups and their supportive social environment and in the temporal sequence of their emergence. Firstly, terrorist groups may emerge from a pre-existing radical milieu, in a gradual process of radicalization. Secondly, both can form at the same time and at the beginning independently from each other, as simultaneous reactions to a perceived threat. Finally, supportive milieus can emerge at a later point in time during a terrorist campaign or as a result of the clandestine group’s deliberate and strategic efforts create open support-groups (what we call “secondary milieus”).

In the first case, militant milieus emerge gradually in the context of escalating confrontations, typically between protest movements and state security forces. Then, over the course of a continuing process of escalation and radicalization, clandestine groups form within these radical milieus. This development often corresponds to a period of decline and fragmentation within the broader movement, when open mobilization recedes and parts of the movement withdraw, which typically triggers a dynamic of radicalization among some groups at the fringe of the movement. Radicalization, thereby, is also the result of violent escalation and controversies around militant forms of action within the movement, with the radical milieu emerging in confrontations with political opponents as well as by delimiting and separating itself from moderate, non-militant parts of the movement. The emergence of terrorist groups, then, follows a further step of radicalization, born out of the perception that previous forms of protest would not suffice. Moving underground represents a crucial incision in the development of militant groups as it reshapes relationships with their social environment, separating the clandestine activists from the broader movement as well as – to some extent – from the radical milieu in which they emerge; and the choice of more extreme violent (terrorist) tactics often undermines non-militant proteststrategies. The emergence of many left-wing clandestine groups from radical milieus within the student movements in the 1970s illustrates this dynamic of escalation and transformation. In the context of increasing confrontations with the police, on the one hand, and a decline of mass mobilization on the other, militant milieus formed among parts of the protest movements and the alternative subculture in Germany and Italy, from which later several clandestine groups emerged. In Berlin, this milieu included groups around the “communes” in Berlin and semiclandestine groups such as the “Hashish Rebels” or the “Tupamaros West-Berlin” and consecutively formed the social environment in which terrorist groups such as the Red Army Faction as well as Movement 2[nd] of June formed. In Italy, so called “marshals-”groups – militant “self-defence” units set up by many of the more radical leftist organizations in the protest movement – played an important role not only in confrontations with political opponents but also as the social context from which many later members of the Brigate Rosse and other clandestine groups originated.[32]

A second pattern in which radical milieus may form is the more or less simultaneous, independent emergence of terrorist groups and a social environment which condones and engages in militant forms of action, with the two then gradually developing closer relationships; a pattern which we call “co-constitution”. This process often takes place in a situation in which a religious or ethnic minority is threatened by violent attacks or repression, triggering the formation of radical milieus and at the same time the emergence of clandestine groups. Coconstitution also involves some connection between radical milieus and violent groups, but the latter do not emerge directly from the former. Rather, the two form in parallel developments which represent different forms of militant reaction to the same challenge. The common defensive impulse often results in the gradual formation of close relationships of solidarity and support. It may even be the case that this social environment calls for or demands clandestine groups to carry out violent attacks as a form of protection or revenge. An example for this process is the Basque country under the Franco-regime and during the period of democratic transition, where in reaction to years of oppression and marginalization a militant protest-milieu as well as the ETA as a clandestine violent organization formed almost simultaneously in the late 1960s. Another example is the relation between the south-Lebanese population and militant groups after the Israeli occupation in 1982. In this case, too, parts of the local population radicalized in reaction to experiences of abuse, oppression, and the perceived threat of expropriation and expulsion, engaging in spontaneous civil resistance and gradually pushing the reluctant Amal-leadership (a Shiite militia) to take part in the emerging violent resistance, and later forming support-relationships with the militant Islamist movement Hizb Allah when they expanded their presence in the South. A third case is Argentina at the end of the 1960s, during the military dictatorship of Carlos Ongania. After several years of relative peace that resulted from paralyzing state-repression, militant mass-protest led by industrial workers and students erupted in several larger cities, while almost simultaneously newly formed “urban-guerrilla”groups started to carry out violent attacks.

These first two types of processes of formation emphasize the independent, autonomous character of radical milieus, which emerge before or simultaneously to the violent groups and develop autonomous social structures and perspectives. Supportive milieus, however, can also form at a later stage, when the clandestine group has already been operating for some time, or even as a product of strategic efforts by terrorist groups to create legal or semi-legal supportorganizations. Over the course of violent campaigns, issues such as state persecution of sympathizers or the imprisonment (and alleged or real abuse in prison) of activists often mobilizes a new following, fuelled by narratives of martyrdom and heroic suffering. Particularly when clandestine groups have become estranged and largely isolated from the radical milieus from which they emerged, or when these milieus have disappeared, these processes of mobilization may result in the formation of new, independent radical milieus, what we term <em>secondary milieus.</em> These can, for example, take the form of militant youth-subcultures around armed groups or legal-aid committees and other support-groups, which may gradually replace original milieus as basis of support and recruitment. In Germany, legal-aid groups such as the socalled <em>Rote Hilfe</em> (“Red Help”) developed during the trials of prominent RAF leaders around the mid-1970s, at a time when the group had become largely isolated from leftist movementsubcultures and gradually became their main supportive milieus and reservoir of new recruits, as several members of the RAF’s second and third generation began their careers within these groups.

It needs to be emphasized at this point that while these three types represent distinct modes of formation they are not mutually exclusive and may overlap in certain cases, with supportive social environments developing in a mixture of original radical milieus that are transformed over time and become intertwined with (and are sometimes challenged by) newly emerging milieus of younger militant supporters. Also, secondary radical milieus which are to some extent “created” by clandestine groups may still be partly autonomous or develop into more independent milieus.

*** 4. Forms and characteristics of radical milieus

Radical milieus as well as their relationship with clandestine groups can take very different forms, ranging from small, dispersed networks of supporters to larger radical milieus rooted in widespread support for a violent campaign among the population of certain neighbourhoods and towns. Radical milieus, in other words, vary, firstly, with respect to their <em>size</em> and with respect to their <em>spatial concentration</em> or dispersion. To a certain extent, size and spatial distribution are shaped by the societal and political context in which radical milieus form, in particular the reach and capacity of state-control and the existence of neglected or partly autonomous spaces. Universities, churches and mosques, or other institutions that are protected by law or custom not only offer some degree of protection from state persecution for movements and emerging radical milieus, but also constitute spatial foci that allow for dense, localized relations to form. Similarly, in shantytowns in the suburbs of larger cities the absence of police and government authorities may give radical milieus room to expand and facilitate spatial concentration. Yet, of similar or even greater influence on the social and spatial extent of radical milieus are political and cultural factors that contribute to the acceptance of violent action among parts of a population. In particular, traditions and social institutions of vigilante justice and violent selfdefence among marginalized communities, as well as notions of collective identity as oppressed minority – and connected perceptions of legitimate violent struggle against a state seen as an alien, occupying force – may facilitate the emergence of radical milieus and create social spaces that government authorities do not regularly enter. Last but not least, the size and spatial distribution of radical milieus is shaped by the size and organizational structure of the terrorist group and the nature of their claims and struggle. While transnationally operating militant networks might draw on support from environments in particular local settings, their overall radical milieu is necessarily spread out over a broader geographic area and its relation to local spaces might not be that of territorially-based groups (see below).

A second aspect in which radical milieus vary is their degree of <em>internal cohesion</em> and patterns of social and political organization. While cohesion is to some extent linked to spatial concentration, it is also influenced by the social makeup of a population, the quality of relationships, as well as the presence of social and political associations and mechanisms of coordination and social control that serve to reinforce cohesion. Related to cohesion, but not equivalent, are differences in the <em>resilience</em> of radical milieus under pressure and their <em>stability</em> over time. Whereas some supportive networks form and disappear quickly, others consolidate and exist as radical milieus supportive of militant groups in a particular struggle for several decades.

Finally, radical milieus differ with respect to the <em>boundary</em> between the milieu and the clandestine group as well as with respect to their “outer” boundary and criteria for membership in the milieu. The former, obviously, is also shaped by the type and structure of the terrorist groups, which may operate in complete clandestinity and communicate even with their supportive milieus only via public statements or very select and secret channels; or they may operate in a more semi-clandestine manner, hiding from police but staying in regular face-to-face contact with their supportive milieu and their families. The degree to which the boundary between the radical milieu and the clandestine group is fluent, or strict and controlled, is also discernible in patterns of recruitment which may be quick and informal or may evolve elaborate selection-processes, security-screening, and training by the militant group. Similarly, the degree to which individuals are allowed to move back and forth between clandestine groups and radical milieus indicates the way in which this boundary is defined and enforced.

To conceptualize different forms of radical milieus we have in previous publications introduced the terms <em>radical community</em> and (transnational) <em>radical network</em>, which represent ideal-types in the Weberian sense and can be understood to mark the extreme ends of a continuum of variation that includes many of the variables mentioned above.[33] We briefly reiterate some of their characteristics in order to summarize and illustrate our argument.

The concept of <em>radical community</em> refers to a pattern of radical milieu that typically emerges within ethnic or religious minorities in segmented societies in reaction to repression, attack, or a perceived threat to their cultural or political identity and autonomy.[34] Examples for this type of radical milieu include the following around the Basque ETA, the militant Republican milieu among the Catholic population in Northern Ireland, or Shiites in southern Lebanon that support Hezbullah. The militant groups to which they relate may have their origin within movements that pursue broader goals, but the radical community emerges mainly from a defensive impulse. Typically, they are spatially concentrated in a certain area as well as in certain neighbourhoods and towns within that area. Moreover, their relation to space is territorial. Collective identities are rooted in notions of historical belonging to and ownership of a certain area and the struggle is defined by claims (and counter-claims) to a certain territory which is to be defended or liberated.

Thereby, the meaning of territory for radical communities goes beyond an abstract “national” project and often involves intimate relations to local spaces such as certain neighbourhoods or towns, and confrontations often revolve around defending these spaces and their boundaries, whether symbolically or with violence.[35] The fact that they emerge within ethnic or religious minorities implies that membership in radical communities tends to be more restricted and largely confined to those belonging to that minority. It also means that outer boundaries are less permeable and often strictly enforced. Minorities, particularly when looking back on a long history of struggle against oppression or occupation, often have formed a broad array of cultural, social, and political associations which also shape the radical community’s internal structure and organization, contributing to their stability over time. The fact that they form in reaction to a perceived threat, together with their “rootedness” in a territory, facilitates the emergence of close ties between radical communities and clandestine groups as well as with parts of their wider social environment. The broader ethnic or religious minorities, while ambivalent about the violent means they use, might still identify with the militants as “our boys” who belong to the community. This particular alliance often rests on relations of trans-generational solidarity – parents supporting their children in their struggle against an enemy perceived as threatening the community – which contributes to its durability and resilience under pressure.[36]

At the other end of this continuum are <em>radical networks</em>, particular such of transnational reach. By that we refer to formative and supportive environments of terrorist groups that operate on a transnational level, which typically consist in networks of individuals and smaller groups that are spatially dispersed and are driven and shaped by rather abstract notions of territories and reference groups. These networks may have partially formed within certain local settings or movements openly mobilizing in a certain country, but they have gradually separated from these contexts to form an autonomous social space of transnational reach. One of the most relevant examples for this type of radical milieus is, of course, al-Qaeda and groups and networks connected to it, such as the jihadist networks in Europe from which terrorist cells such as the 7/7 bombers or the “Sauerland-group” in Germany emerged.[37] The fact that their relation to local settings is much more flexible and fluent is also discernible from the fact that they frequently move their activities – from one city or area to another, or from mosques to private homes – in reaction to persecution or tighter control over certain spaces, rather than defending them; which stands in stark contrast to radical communities. While they refer to notions of territories to be defended (Muslim countries invaded by foreign enemies), transnational radical networks themselves do not have a territorial quality, neither in the sense of being connected to and “rooted in” certain local settings, nor in the sense of being shaped by a sense of place and territorial belonging. With respect to their boundaries, radical networks seem at the same time more open and more secretive and restrictive than radical communities. Membership is in principle not restricted to a certain group of people (particularly when considering the rising number and role of European converts in jihadist networks) and the boundaries between the radical network and terrorist cells are relatively fluent. Yet, because their connection to wider movements or communities is weaker, and because they tend to operate secretively, radical networks are rather closed semi-clandestine formations. With respect to resilience and stability, radical networks do not seem to be as long-lasting as radical communities, inter alia because they are not territorially and socially “rooted” and because the terrorist groups to which they are linked are constantly changing. But their flexibility and more dispersed structure also allows them to evade and adapt to repression and quickly re-build after setbacks, exactly because of their only loose connection to certain spaces and the fluent quality of organizational structures.

*** 5. Relationships between radical milieus and their socio-political environment: Dynamics of radicalization, self-separation, and fragmentation

As emphasized above, radical communities as well as (transnational) radical networks are idealtypes that mark a spectrum on which empirical cases of radical milieus can be analytically located. Thereby, radical milieus are not static but dynamic, constantly re-negotiated relational formations that are transformed over the course of violent conflicts. The processes in which they emerge and evolve are shaped, in particular, by interactions with their wider political and societal environment, on the one side, and by relations with the violent group, on the other side. We first turn to the first mentioned “outside” relations, among which relations with two kinds of environments are particularly important: state security services (or political opponents) and the wider social movement or ethnic or religious community from which the radical milieu emerged.

The relationship between radical milieus and security forces (and political opponents) is highly conflictive and plays a paramount role in the emergence of radical milieus as well as in constantly re-shaping them over the course of violent campaigns. Radical milieus are located, in a sense, at the centre of confrontations and are often the main target of police-persecution as well as of attacks by political opponents. In early stages, its members participate in militant protests at demonstrations and clashes with the police; and when clandestine groups have emerged, security forces often particularly target their (alleged or real) supportive environment either because they are unable to locate or identify the terrorists themselves or as part of a deliberate strategy to undermine relationships between terrorist groups and radical milieus. Interactions with security forces thus contribute to the dynamics of escalation and radicalization from which radical milieus emerge. For its members, thereby, the radical milieu represents a formative environment in which they experience police-persecution and violent confrontations, and in which interpretative frameworks are constructed and violent repertoires of action developed. Social networks, personal loyalties, as well as forms of communication and organization that enable activists to resist persecution and sustain activism are developed within this social environment and as a result of common experiences in the context of violent confrontations. Historic and more recent examples for the radicalizing effects of confrontative interactions between protest movements and police or political opponents – and their importance for the emergence of radical milieus – abound. In Germany, the death of Benno Ohnesorg, shot and killed by a policeman during a demonstration in Berlin in June 1967, had tremendous effects on parts of the student movement and triggered a wave of radicalization that saw the emergence of several clandestine groups, one of which was, in fact, named after the incident (Movement 2[nd] of June). In the Basque country, conditions in prisons and the torture of suspected Basque nationalist activists contributed significantly to the escalation of the conflict. In Northern Ireland, attacks on Catholic neighbourhoods in Belfast by Protestant gangs had similar escalating effects. Jihadist milieus in Europe, such as the radical network around the “Sauerland-Group” in Germany, also seem to have emerged from what they perceived as persecution of their movement by police and intelligence agencies, which in their frame of interpretation became linked to ongoing wars in Iraq or Afghanistan, as part of the global oppression of Muslims.[38] In this case, in other words, experiences of threat and persecution were to some extent visceral, rather than direct, and had mobilizing power largely because they were interpreted within a wider framework of interpretation that emphasized injustices and suffering of a global reference group.

Continuing persecution and attacks by opponents over the course of violent conflicts, then, can vary in their effect on radical milieus. They may result in a consolidation and hardening of resistance among parts of the milieu, and particularly outrageous events can result in waves of mobilization within the broader movements or communities. Yet, repressive measures may also contribute to the encapsulation and isolation of radical milieus within broader movements, their spatial displacement, or the fragmentation and disintegration of supportive milieus before they can consolidate. In the case of the Basque country and Northern Ireland, signs of weakness or internal frictions became visible at different points in time, often as a result of pressure from the police and war-weariness after years of violent struggle. Yet, events such as the death of Bobby Sands during huger-strikes in Northern Irish prisons also were able to trigger waves or (re)mobilization and to strengthen the radical milieus. In the case of the jihadist cells in Germany, the radical network as well as the wider Salafist milieu was continually re-shaped by pressure from government authorities, which included the repeated closure of mosques and legal actions against a broad range of individuals and groups connected to the network. These measures had the effect of displacing the milieu, with militant as well as non-militant activists moving to other parts of Germany or to Egypt and Saudi-Arabia and possibly contributed to further radicalizing members of the radical network, many of whom joined the violent jihad in Afghanistan and later in Syria.[39]

In sum, we can observe that interactions with police and political opponents not only contribute to the formation of radical milieus but also re-shape them over the course of violent conflicts. Yet, as important as these dynamics are, the formation of radical milieus should not be explained simply as a reaction to repression. Most crucially, radical milieus also form in interaction with – and separation from – the wider movements and communities from which they emerge. Different groups within the same movement compete over support from their followers and over mediaattention, which can entail dynamics of political outbidding between rival groups resulting in a shift to more militant political positions and tactics. Moreover, radical milieus and frames of interpretation are formed in delimitation from moderate parts the movement, often in a polarizing, conflictive dynamic of self-separation, with militant activists accusing mainstreamleaders of betrayal, selling out the objectives and values of the movement, or even of collaboration with the enemy. Radical, uncompromising positions and militant forms of action then are stylized as the only true (or the only effective) way forward, and those who adopt them see themselves as the select few who remained true to the cause. Radical milieus and frames of interpretation, in other words, are often formed as much by separating oneself from – and by denouncing and attacking – moderate groups and leaders within the same movement or community, as they are in confrontations with opponents. And it might even be for these “internal enemies”, or “traitors”, that radical activists reserve their most fierce hostility and contempt.

The German student movement of the 1960s also provides examples for this process. Its militant wing was proud of its stigmatization in the media and advanced its separation from the movement’s mainstream, which it considered too accommodating and its moderate protest ineffective. Even more pronounced was the dynamic of self-separation from a moderate mainstream in the case of jihadist and radical right-wing milieus in Western Europe. The Hofstad-network, to which the murder of Theo van Gogh was connected, as well as radical milieus in London which emerged around certain mosques and preachers formed in reaction to what they perceived as betrayal by the mainstream Muslim communities who too willingly collaborated with initiatives and programmes of social inclusion offered by the British and Dutch governments. Members of the Hofstad network were deeply disappointed by the Salafist mainstream in the Netherlands that had shifted towards a more moderate rhetoric after 2002, which drove the activists towards increasingly radical ideas and was, as de Koning argues, a significant factor in shaping the radical network.[40] Similarly, within the German radical right, militant activists considered the direction taken by the right-wing party NPD as too soft, prompting groups among the semi-clandestine “Kameradschaften” to take a different course and carry out violent acts to “cleanse the German people from foreign elements”, as they saw it.[41]

*** 6. Relationships between terrorist groups and radical milieus: Dynamics of support and control; encapsulation and isolation

With respect to the relationship between radical milieus and clandestine violent groups it is important to understand that the two represent different forms of militant activism for the same cause and objective – challenging the state or political opponents by violent means – and that they emerge in close connection with each other. They share frameworks of interpretation that refer to injustices and suffering to legitimize and give meaning to their struggle, and which identify common constituencies, opponents, and enemies. And they share experiences of violent confrontations and police persecution. Their relationship, thus, is characterized, firstly, by a shared understanding of being allies in their struggle and a notion of basic solidarity, which unites and connects radical milieus and terrorist groups. Even if conscious about the fact that the two represent different forms of commitment, clandestine activists recognize the radical milieu as belonging to the same side and as being committed to the right struggle. The members of the “Sauerland-Group”, for example, considered activists within the radical network as “good brothers” who shared their commitment to violent jihad; and when they discussed the arrest of a group of young men on their way to training camps in Afghanistan, it was clear that “they were people from us”, meaning that they belonged to the same radical network from which the group emerged.

A second feature of the relationship between radical milieus and clandestine groups, which results from their shared origin, identity, and mutual orientation, is the basic willingness on the part of the radical milieu to politically and logistically support the clandestine activists. Logistical support includes offering shelter and other assistance to activists on the run from the police, providing means of transport or conveying messages, hiding items in private homes, donating money, or assisting in legal and illegal businesses to generate funds. Political and moral support, which often is equally or more important to clandestine groups, may take the form of demonstrations to protest against the treatment of political prisoners or other perceived injustices, attending the funeral of killed members of the clandestine groups, painting slogans or putting up posters in support of the group, or staging publicity- or electoral-campaigns organized by legal political groups or parties, such as Sinn Fein in Northern Ireland, which act as public advocates of their common cause and seek to generate political pressure to parallel and support the violent campaigns. This relation may evolve into a closely coordinated, almost symbiotic relationship between radical milieu and the terrorist group, in which the radical milieu “authorizes” and “delegates” the use of certain forms of violence to the armed group and acts as its legal arm, publicly legitimizing attacks and seeking to transform them into political momentum.

The relationship between radical milieus and clandestine groups thus entails mutual orientation and dependency and, thereby creates leverages of influence. This is insofar relevant as, notwithstanding notions of basic solidarity, a third feature of the relationships between terrorist groups and their immediate social environment is the fact that they always include an element of tension, disagreement, or even conflict. There are several reasons for this. In general, it has to be emphasized that radical milieus do not support terrorist groups without any reservation and do not condone any form of violent attacks. In most cases there are clear limits to what radical milieus consider legitimate or acceptable in terms of the number of victims, targeting patterns (i.e. indiscriminate attacks, harming innocent bystanders, in particular children and women), or forms of violence (i.e. particularly gruesome attacks, mutilations, the use of suicide bombers). Moreover, there are limits to what is tolerated in terms of repercussions for the milieu and the wider community in the form of repression by the police or attacks by opponents provoked by the clandestine group’s violent campaign. Thereby, two mechanisms of influence can be distinguished. The first is based on abstract normative orientation towards the radical milieu. In other words, terrorist groups may constrain their use of violence because of what they perceive (or know) to be norms and values held by the radical milieu with respect to the use of violence. They take these into account when choosing targets and tactics, and on that basis may refrain from certain violent attacks. The second way in which radical milieus may influence clandestine groups is in the form of directly communicating approval or disapproval, withdrawing support, or even openly confronting them. Clandestine groups may face criticism or resistance in reaction to violent acts or tactics when they overstep what are perceived as boundaries of acceptable violence or when their violent tactics incur excessive costs in terms of own losses or staterepression, which may provoke various forms of disapproval and opposition, culminating in the withdrawal of support.

Well known examples for these forms of constraining influence include the Enniskillen bombattack by the PIRA in 1987, which killed ten civilians and injured many more, shocking many Republicans and provoking severe criticism among the group’s supporters, which pushed the militants to adapt their tactics (and even disband the unit responsible for the attack). Another example is the bombing at a shopping mall in Omagh in 1998, which killed 29 people and created a severe crisis of support for the Real IRA, forcing them to apologize and shortly after cease their violent campaign. The murder of Edward Pimental, a U.S. soldier based in Germany, by the Red Army Faction for the sole purpose of taking from him his ID-card in order to carry out a bomb-attack on the Rhein-Main Air Base similarly provoked fierce discussions among radical leftist circles, including its supportive milieus, which affected the group’s tactical choices later on. An interesting case of a clandestine group reacting to criticism and resistance by radical milieus at an early point in time, refraining from further escalating its violent campaign – or even disengaging from it – is the Weather Underground organization as described by Falciola.[42] After engaging on what seemed to be a trajectory of escalating terrorist violence in 1969/1970, the group started to limit their attacks to “symbolic” bombings shortly after, largely due to criticism and an increasing a loss of support among the radical milieu. The case of the “Sauerland Group”, finally, illustrates the constraining influence of normative orientation. Two of the four members of the groups had, at some point in time, serious doubts about the planned bombings in Germany, which led one of the two to eventually leave the group. Whereas “defensive” jihad in Muslim countries was unanimously approved by members of the radical network as well as by many in the wider Salafist movement in which the young men had been “socialized”, terrorist attacks in Europe were far more controversial, raised issues of legitimate targets and civilian casualties, and did not correspond to their role model of the heroic mujahedeen in the Hindukush.[43]

In many cases, the combination of basic solidarity and support on the one hand and tensions over the use of violence on the other results in a process of permanent negotiation between clandestine groups and their immediate social environment, with the armed groups at times confining their violent tactics to anticipated limits of support, and at times testing theses boundaries (and later responding to resistance by adapting their campaign). The Provisional IRA, for example, as former IRA-member Eamon Collins put it: ”– regardless of their public utterances dismissing the condemnations of their behaviour from church and community leaders – tried to act in a way that would avoid severe censure from within the nationalist community; they knew they were operating within a sophisticated set of informal restrictions on their behaviour, no less powerful for being largely unspoken“.[44] As Darby further shows, this was accompanied by the militant group testing the limits of what their social environment tolerated in terms of targets and forms of violent attacks, while at the same time creating and using a legitimatory discourse to counter anticipated criticism and condemnations even before they carried out an attack.[45] In some cases, this negotiation and the debates that accompany it are relatively open, taking place in newsletters and other media circulated also within the wider movement or community; or criticism is voiced publicly by political or religious leaders respected within the milieu. In other cases, disapproval is communicated in private face-to-face encounters with friends of family-members; or it might be discernible only in the form of silences and the absence of voices that normally would condone an attack.

Due to their relationship of mutual dependence and orientation, many terrorist groups cannot afford to completely ignore this kind of resistance from their immediate social environment, on which they rely as a source of support and recognition, resulting in forms of influence and constraints on violent practices. And under certain circumstances, when war-weariness and doubts about the legitimacy of violent attacks have spread within the radical milieu, this social environment may even become a crucial force in initiating and sustaining processes of disengagement from political violence. Yet, it has to be emphasized that there are limits to the radical milieu’s influence and that clandestine groups also use various means, including violence, to control dissidence within the radical milieu. There often is an element of coercion to the relationship between violent groups and the milieus from which they expect support, for example when militants “police” communities and, in particular, punish or kill alleged traitors or those who “collaborate with the enemy”, an accusation that is often used to isolate or eliminate critics. In some cases, thus, opposition from within the radical milieu may have just the opposite effect of radicalizing the group and undermining their relationship with the radical milieu. Clandestine groups then interpret resistance from their former supporters as betrayal, at times trying to coerce them into providing assistance and into refraining from collaborating with their opponents, which often results in the armed group further isolating itself underground in a dynamic of radicalization and encapsulation that leads, in some cases, to a loss of constraints over violent practices.[46]

*** 7. Benefits and uses of the concept

The <em>radical milieu</em> represents what could be called a conceptual “missing link” in research on political violence. We argue that processes of political violence and the logic of action of clandestine groups are crucially shaped by the relationships between these groups and their immediate – formative and supportive – social environment. By identifying and specifying this social environment as an intermediate social formation between armed groups and their wider context, the concepts enables us to more precisely analyse two sets of relationships: those between clandestine groups and radical milieus as well as relations between the radical milieu and its wider social environment. It thus contributes to further developing a contextualizing, relational perspective on processes of political violence, which emphasizes specific patterns of relationship and dynamics of interactions, rather than abstract contextual factors. This perspective opens new ways of explaining the emergence and development of terrorist violence. The concept of radical milieu emphasizes collective political experiences and processes of interaction and points to the ways in which notions of identity and solidarity form and are sustained. Moreover, it allows to analyse the process of group-formation in their relational quality: based on personal ties and social networks within the radical milieu and in interaction with their wider social environment.

Due to their intermediate location in the constellation of actors, radical milieus are characterized by their profoundly ambivalent role in processes of political violence. For individual activists, the radical milieu is the formative environment, the milieu in which they are socialized and adopt frameworks of interpretation, values and symbols, and in which they share experiences of persecution and violent confrontations. And it includes the social networks and friendship ties that shape their pathway into clandestine groups and which emotionally reinforce their commitment and solidarity. Yet, the radical milieu is not simply a “hotbed” of radicalization for individuals, but also prevents many activists from taking the last step of joining terrorist groups. Of relatively many militant activists within this environment, only quite few participate in violent groups. While, on the one hand, representing a milieu that may contribute to processes of radicalization, the radical milieu, on the other hand, also constitutes an environment which, for various reasons, may constrain these pathways by offering, for example, alternative forms of activisms as well as social networks which represent alternative opportunities for activists to leave trajectories of radicalization short of joining terrorist groups, as well as a place to go – a viable “exit”-option – for activists who disengage from violent clandestine groups. Even when they wish to leave terrorist groups, many militant activists stay if the only option they have is breaking completely with their political beliefs and betraying their comrades. The radical milieu insofar, offers a way to continue the struggle while disengaging from violence.

On the collective level, the ambivalent role of the radical milieu manifests itself in the fact that clandestine groups depend on a certain extent of support from this immediate social environment while, on the other hand, their relationship is characterized by tensions and conflicts over the use of violence, which may result in constraining effects on the armed group’s choice of tactics and levels of violence, as discussed above. Thereby, the degree to which the radical milieu is able to exert this constraining influence on the violent group depends on how close their relationship is, and to what extent the clandestine groups depends on support from this environment; but also on how autonomous the milieu is in relation the clandestine groups. The duration of the violent conflict, thereby, plays an important role. During the initial phases of a protest- or resistance-movement, anger and outrage are widespread, unifying support for the militants and overshadowing internal differences. Only later, internal conflicts and different interests resurface again, also as a result of war-weariness. In this phase, radical milieus and legal support groups often play an important role in connecting clandestine groups – which always run the danger of getting isolated and disconnected from realities – and with evolving social and political preferences and perspectives within the wider movement or community. The radical milieu thus represents a “safeguard”-mechanism to prevent irrational developments and excesses in later phases of violent campaigns, and plays a crucial role in sustaining peace-processes and the disengagement from political violence.

Yet, these mechanisms – and the elements of constraint they entail – get lost with the breakdown of the relationship between clandestine groups and their supportive social environment. Thus, clandestine groups and trajectories of political violence can be distinguished according to relationship-patterns between clandestine groups, radical milieus, and their wider social environment, and according to the types of relationships and dynamics of interaction that link clandestine groups and their immediate social environment. This relationship not only shapes resilience and capabilities of violent groups, but also may contribute significantly to explaining the evolution of violent groups over time and trajectories of escalation, radicalization, or disengagement from political violence.

[1] Our understanding of the concept of terrorism refers to Waldmann’s definition as a campaign of premeditated violent attacks by clandestine groups against a political order, designed to spread fear and insecurity but also to create sympathy and support among other groups. See Peter Waldmann, <em>Terrorismus: Provokation der Macht</em> (München, Gerling Akademie Verlag 1998), p.10. See also Martha Crenshaw, <em>Revolutionary Terrorism: The FLN in Algeria, 1954-</em><em>1962</em> (Stanford: Hoover Institution Press 1978), p. 19–21, Martha Crenshaw, “Thoughts on Relating Terrorism to Historical Contexts,” in M. Crenshaw (ed.), <em>Terrorism in Context</em> (University Park, Pennsylvania: The Pennsylvania State University Press, 1995), p. 4. For a critical discussion of the concept of terrorism see Charles Tilly, “Terror, terrorism, terrorists,” <em>Sociological Theory</em> 22, no. 1 (2004): 5–13; Jeroen Gunning, “A Case for Critical Terrorism Studies,” <em>Government and Opposition</em> 42, no 3 (2007): 372/3; Jeroen Gunnin, “Social Movement Theory and the Study of Terrorism,” in R. Jackson, M. B. Smyth, J. Gunning (eds.), Critical Terrorism Studies: A New Research Agenda (London: Routledge, 2009), p. 157/161; Jeff Goodwin, “Terrorism,” in E. Amenta, K. Nash, and A. Scott (eds.), <em>The WileyBlackwell Companion to Political Sociology</em> (pp. 190–203) (London: Blackwell 2012).

[2] For a discussion of our use of the terms “radicalization” and “radical” see below, section 2.

[3] See Peter Waldmann, “The radical milieu: The under-investigated relationship between terrorists and sympathetic communities,” <em>Perspectives on Terrorism</em> 2, no. 9 (2008): 25–27.

[4] For an overview of the literature on terrorist violence see Magnus Ranstorp, <em>Mapping terrorism research: State of the art, gaps and future direction</em> (London and New York: Routledge, 2007); and Alex P. Schmid, <em>The Routledge Handbook of Terrorism Research</em> (London: Routledge, 2011).

[5] See inter alia Jeroen Gunning, “A Case for Critical Terrorism Studies,” <em>Government and Opposition</em> 42, no 3 (2007): 372/3; Jeroen Gunnin, “Social Movement Theory and the Study of Terrorism,” in R. Jackson, M. B. Smyth, J. Gunning (eds.), <em>Critical Terrorism Studies: A New Research Agenda</em> (London: Routledge, 2009), p. 157/161; Richard Jackson, Marie Breen Smyth, Jeroen Gunning, “Introduction: The Case for Critical Terrorism Studies,” in R. Jackson, M. B. Smyth, J. Gunning (eds.), <em>Critical Terrorism Studies: A New Research Agenda</em> (London: Routledge, 2009).

[6] See for example Crenshaw, “Revolutionary Terrorism“ (see note 1 above); Crenshaw, “Terrorism in Context” (see note 1 above); David Rapoport (ed.), “Inside Terrorist Organizations”, Special Issue of <em>The Journal of Strategic Studies</em>, 10(4) (1987); Donatella Della Porta, <em>Social Movements, Political Violence, and the State: A Comparative Analysis of Italy and Germany</em> (Cambridge: Cambridge University Press 1995); Waldmann,“Terrorismus” (see note 1 above); Peter Waldmann, <em>Ethnischer</em> <em>Radikalismus: Ursachen und Folgen gewaltsamer Minderheitenkonflikte</em>, (Opladen: Westdeutscher Verlag, 1989).

[7] Among the most notable works are, for example: Marc Sageman, <em>Understanding Terror Networks</em> (Philadelphia: 2004); Marc Sageman, <em>Leaderless Jihad</em> (Philadelphia: 2008); John Horgan, “From Profiles to Pathways and Roots to Routes: Perspectives from Psychology on Radicalization into Terrorism.” <em>The Annals of the American American Academy of Political and Social Science</em> 618, no 1 (2008): 80–94; John Horgan, <em>Walking Away from Terrorism: Accounts of Disengagement from Radical and Extremist Movements</em> (London: 2009); Peter Neumann, “Recruitment and Mobilisation for the Islamist Militant Movement in Europe”, London: 2008, [[https://ec.europa.eu/justice_home/fsj/terrorism/prevention/docs/ec_radicalisation_study_on_mobilisation_tactics_en.pdf][ec.europa.eu]] (08.06.2009); Peter Neumann, <em>Joining Al-Qaeda: Jihadist Recruitment in Europe</em> (London, 2009); Clark McCauley and Sophia Moskalenko, “Mechanisms of Political Radicalization: Pathways Toward Terrorism,” <em>Terrorism and Political Violence</em> 20, no. 3 (2008): 415–433; Thomas Hegghammer, Jihadism in Saudi Arabia (Cambridge: Cambridge University Press 2010).

[8] This is true, in particular, for a recently consolidating literature on political vionece that adopted theoretical approaches from social movement studies. See, inter alia: Eitan Alimi, “Relational Dynamics in Factional Adoption of Terrorist Tactics: a Comparative Perspective,” <em>Theory and Society</em> 40, no. 1 (2011): 95–119; Lorenzo Bosi, “Explaining Pathways to Armed Activism in the Provisional IRA, 1969–1972,” <em>Social Science History</em> (forthcoming); Eitan Alimi, Lorenzo Bosi, and Chares Demetriou, ” Relational Dynamics and Processes of Radicalization: A Comparative Framework,” <em>Mobilization</em> 17, no 1 (2012): 7–26; Lorenzo Bosi, Chares Demetriou, and Stefan Malthaner, Stefan (eds.), <em>Dynamics of Political Violence</em> (London: Ashgate 2014); Della Porta, <em>“Social Movements, Political Violence, and the State”</em> (see note 6 above); Donatella Della Porta, “Research on Social Movements and Political Violence,” <em>Qualitative Sociology</em> 31 (2008): 221–230; Donatella Della Porta, <em>Clandestine Political Violence</em> (Cambridge; Cambridge Universtiy Press 2013); Jeroen Gunnin, “Social Movement Theory and the Study of Terrorism” (see note 1 above); Hegghammer, “Jihadism in Saudi Arabia” (see note 7 above); Stefan Malthaner, <em>Mobilizing the Faithful: The Relationship between Militant Islamist Groups and their Constituencies</em> (Frankfurt/New York: Campus, 2011); Gilda Zwerman, Patricia G. Steinhoff and Donatella della Porta, “Disappearing Social Movements: Clandestinity in the Cycle of New Left Protest in the US, Japan, Germany and Italy,” <em>Mobilization</em> 5 (2000): 83–100; but also for a number of works on individual pathways of radicalization, such as: John Horgan, “From Profiles to Pathways and Roots to Routes” (see note 7 above); John Horgan, “Walking Away from Terrorism” (see note 7 above); Clark McCauley and Sophia Moskalenko, “Mechanisms of Political Radicalization” (see note 7 above).

[9] Gianfranco Pasquino and Donatella Della Porta, „Interpretations of Italian left-wing terrorism,“ in P.H. Merkl (ed.), <em>Political violence and terror: Motifs and motivations</em> (pp. 169–189) (Berkeley, Los Angeles: University of California Press, 1986); Della Porta, <em>“Social Movements, Political Violence, and the State”</em> (see note 6 above); Della Porta, “Clandestine Political Violence“ (see note 8 above); Wanda Baeyer-Katte, Dieter Claessens, Hubert Feger, Friedhelm Neidhardt, <em>Gruppenprozesse</em><em>.</em> <em>Bundesministerium des Innern, Analysen zum Terrorismus Bd. 3</em> (Opladen: Westdeutscher Verlag, 1982); Friedhelm Neidhardt, “Gewalt und Gegengewalt: Steigt die Bereitschaft zu Gewalteskalation mit zunehmender staatlicher Kontrolle und Repression?,” in Heitmeyer et al. (eds.), <em>Jugend – Staat – Gewalt: Politische Sozialisation von Jugendlichen, Jugendpolitik und politische Bildung</em> (pp. 233–243) (Weinheim/München: Juventa, 1989).

[10] See Quintan Wiktorowicz, “Islamic Activism and Social Movement Theory,” in Q. Wiktorowicz (ed.), <em>Islamic Activism: A Social Movement Perspective</em> (pp. 1–36) (Bloomington & Indianapolis: Indiana University Press, 2004). See also Mohammed M. Hafez, Why Muslims rebel: Repression and resistance in the Islamic world (Boulder: Lynne Rienner, 2003); Mohammed M. Hafez, “From Marginalization to Massacres: A Political Proces Explanation of GIA Violence in Algeria,” in Q. Wiktorowicz (ed.), <em>Islamic Activism: A Social Movement Perspective</em> (pp. 37–60) (Bloomington & Indianapolis: Indiana University Press, 2004); Mohammad M. Hafez and Quintan Wiktorowicz, “Violence as Contention in the Egyptian Islamic Movement,” in Q. Wiktorowicz (ed.), <em>Islamic Activism: A Social Movement Perspective</em> (pp. 61–88) (Bloomington & Indianapolis: Indiana University Press, 2004); Malthaner, “Mobilizing the Faithful” (see note 8 above).

[11] Alimi, “Relational Dynamics in Factional Adoption of Terrorist Tactics“ (see note 8 above); Alimi/Bosi/Demetriou, ”Relational Dynamics and Processes of Radicalization: A Comparative Framework” (see note 8 above); Della Porta, “Clandestine Political Violence“ (see note 8 above); Bosi/Demetriou/Malthaner, „Dynamics of Political Violence“ (see note 8 above).

[12] Della Porta, “Social Movements, Political Violence, and the State” (see note 6 above), pp. 113–119; Della Porta, “Clandestine Political Violence“ (see note 8 above), pp. 146–153).

[13] For example: Crenshaw, “Revolutionary Terrorism“ (see note 1 above); Crenshaw, “Terrorism in Context” (see note 1 above); Waldmann, “Terrorismus” (see note 1 above).

[14] Crenshaw, “Terrorism in Context” (see note 1 above): 14–18; Friedhelm Neidhardt, “Handlungsfeld Terrorismus: Täter, Opfer, Publikum,” in Berlin Brandenburgische Akademie der Wissenschaften (Hrsg.), Berichte und Abhandlungen, Bd. 2 (pp. 131–144) (Berlin: Akademie Verlag, 2006), p. 136; Peter Waldmann, “Terrorismus und Guerilla: Ein Vergleich organisierter antistaatlicher Gewalt in Europa und Lateinamerika,” in U. Backes und E. Jesse (eds.), <em>Jahrbuch Extremismus und Demokratie</em> (pp. 69–103) (Bonn: Bouvier Verlag); Waldmann, “Terrorismus” (see note 1 above).

[15] Crenshaw, “Terrorism in Context” (see note 1 above), p. 17.

[16] Crenshaw, “Terrorism in Context” (see note 1 above), p. 15.

[17] Frank Burton, <em>The politics of legitimacy: Struggles in a Belfast community</em> (London: Routledge & Kegan Paul, 1978); Jeffrey Sluka, <em>Hearts and Minds, Water and Fish: Support for the IRA in a Northern Irish Ghetto</em> (Greenwich/London: Emerald 1989); Joseba Zuleika, <em>Basque Violence: Metaphor and Sacrament</em> (Reno/Nevada: University of Nevada Press, 1988).

[18] Della Porta, “Social Movements, Political Violence, and the State” (see note 6 above); Della Porta, “Clandestine Political Violence“ (see note 8 above).

[19] Lorenzo Bosi, “Explaining Pathways to Armed Activism in the Provisional IRA” (see note 8 above); Lorenzo Bosi and Donatella Della Porta, “Micro-mobilization into armed groups: the ideological, instrumental and solidaristic paths” <em>Qualitative Sociology</em>, 35 (2012): 361–383.

[20] Fernando Reinares, Patriotas de la muerte: por qué han militado en ETA y cuándo abandonan (Madrid: Taurus, 2001).

[21] Marc Sageman, <em>Understanding Terror Networks</em> (Philadelphia: 2004); Marc Sageman, <em>Leaderless Jihad</em> (Philadelphia: 2008); Mitchell D. Silber and Arvin Bhatt, “Radicalization in the West: The Homegrown Threat, Police Department City of New York,” 2007, [[https://www.nyc.gov/html/nypd/downloads/pdf/public_information/NYPD_Report-Radicalization_in_the_West.pdf][www.nyc.gov]] (08.06.2009); Quintan Wiktorowicz, <em>Radical Islam Rising: Muslim Extremism in the West</em> (Lanham: 2005); Peter Neumann, “Recruitment and Mobilisation for the Islamist Militant Movement in Europe”, London: 2008, [[https://ec.europa.eu/justice_home/fsj/terrorism/prevention/docs/ec_radicalisation_study_on_mobilisation_tactics_en.pdf][ec.europa.eu]] (08.06.2009); Peter Neumann, <em>Joining Al-Qaeda: Jihadist Recruitment in Europe</em> (London: 2009); Hegghammer, “Jihadism in Saudi Arabia” (see note 7 above).

[22] Donatella Della Porta, “Social Movement Studies and Political Violence,” Lecture at the Centre for Studies in Islamism and Radicalization, Department of Political Science, Aarhus University, Denmark, May 29, 2009.

[23] Peter Neumann, “Recruitment and Mobilisation for the Islamist Militant Movement in Europe” (see note 21 above).

[24] Wiktorowicz, “Radical Islam Rising” (see note 21 above).

[25] Lene Kühle and Lasse Linedkilde, “Radicalization among Young Muslims in Aarhus,” Research report prepared for the Centre for Studies in Islamism and Radicalisation (CIR), Aarhus University, Denmark, January 2010.

[26] The concept has first been introduced in: Peter Waldmann, “The radical milieu” (see note 3 above); and further developed in: Stefan Malthaner and Peter Waldmann (eds.), Radikale Milieus: Das soziale Umfeld terroristischer Gruppen (Frankfurt/New York: Campus, 2012). See also Peter Waldmann, Matenia Sirseloudi, and Stefan Malthaner, “Where does the radicalization process lead? Radical communities, radical networks, and radical subcultures,” in M. Ranstorp (ed.), <em>Understanding violent radicalization</em> (London: Routledge 2009); Peter Waldmann, “Mitgliederstruktur, Sozialisationsmedien und gesellschaftlicher Rückhalt der baksischen ETA,” <em>Politische Vierteljahresschrift</em> 22 (1981): 45–68; Peter Waldmann, “Wann schlagen politische Protestbewegungen in Terrorismus um? Lehren aus den Erfahrungen der 70er Jahre,” in A. Randelzhofer und W. Süß (eds.), <em>Konsens und Konflikt: 35 Jahre Grundgesetz.</em> <em>Berlin</em> (Berlin/New York: de Gruyter, 1986); Peter Waldmann, “Ethnic and sociorevolutionary terrorism: A comparison of structures,” <em>International Social Movement Research</em> 4 (1992): 237–257; Peter Waldmann, “The radical community: A comparative analysis of the social background of ETA, IRA, and Hezbollah,” in J. Victoroff (ed.), <em>Tangled roots: Social and psychological factors in the genesis of terrorism</em> (pp. 133–146) (Amsterdam: IOS Press, 2006).

[27] For a discussion of the concept of milieu see Michael Vester, “Alternativbewegungen und neue soziale Milieus: Ihre soziale Zusammensetzung und ihr Zusammenhang mit dem Wandel der Sozialstruktur,” in S. Reichhardt und D. Siegfried (eds.), Das Alternative Milieu: Antibürgerlicher Lebensstil und linke Politik in der Bundesrepublik Deutschland und Europa 1968–1983 (p. 27–59) (Göttingen: Wallstein Verlag 2010); Stefan Hradil, “Soziale Milieus – eine praxisorientierte Forschungsperspektive,” <em>Aus Politik und Zeitgeschichte</em> 44–45 (2006): 3–10; as well as Dieter Rucht, “Das alternative Milieu in der Bundesrepublik,” in S. Reichhardt und D. Siegfried (eds.), Das Alternative Milieu: Antibürgerlicher Lebensstil und linke Politik in der Bundesrepublik Deutschland und Europa 1968–1983 (p. 61–87) (Göttingen: Wallstein Verlag 2010).

[28] For a critique of the terms “radical” and “radicalism” see inter alia Mark Sedgwick, “The concept of radicalization as a source of confusion;” Terrorism and Political Violence 22 (2010): 479–494; and Jeff Goodwin, A Radical Critique of the Radicalization Perspective on Terrorism (forthcoming).

[29] See Malthaner, “Mobilizing the Faithful” (see note 8 above); Stefan Malthaner, “Terroristische Bewegungen und ihre Bezugsgruppen: Anvisierte Sympathisanten und tatsächliche Unterstützer,“ in P. Waldmann (ed.), <em>Determinanten</em> <em>des Terrorismus</em> (pp. 84–137) (Weilerswist: Velbrück Verlag, 2005); Friedhelm Neidhardt, “Terrorism: Conditions and Limits of Control,” in W. Heitmeyer, H.-G. Haupt, S. Malthaner, A. Kirschner (eds.), <em>Control of Violence: Historical and International Perspectives on Violence in Modern Societies</em> (pp. 431–444) (New York: Springer, 2011).

[30] See Malthaner, “Terroristische Bewegungen und ihre Bezugsgruppen” (see note 29 above); Neidhardt, “Terrorism: Conditions and Limits of Control” (see note 29 above).

[31] Malthaner, “Mobilizing the Faithful” (see note 8 above).

[32] See Della Porta, “Social Movements, Political Violence, and the State” (see note 6 above); Della Porta, “Clandestine Political Violence“ (see note 8 above), p. 80–82.

[33] Waldmann, “The radical community” (see note 26 above); Waldmann et al. “Where does the radicalization process lead?” (see note 26 above).

[34] Waldmann, “The radical community” (see note 26 above).

[35] Waldmann, “The radical community” (see note 26 above); on territoriality see also Niall O’Dochartaigh and Lorenzo Bosi, “Territoriality and mobilization: The civil rights campaign in Northern Ireland,” <em>Mobilization</em> 15(4) (2010): 405–24.

[36] Waldmann, “The radical community” (see note 26 above); Waldmann et al. “Where does the radicalization process lead?” (see note 26 above).

[37] See Stefan Malthaner, “Contextualizing Radicalization: The emergence of the “SauerlandCell” from radical networks and the Salafist movement,” <em>Studies in Conflict and Terrorism</em> 37(8) (2014): 638–653.

[38] See Malthaner, “Contextualizing Radicalization” (see note 37 above); Stefan Malthaner and Klaus Hummel, “Islamistischer Terrorismus und salafistische Milieus: Die „Sauerland-Gruppe’ und ihr soziales Umfeld,” in S. Malthaner and P. Waldmann (eds.). <em>Radikale Milieus: Das soziale Umfeld terroristischer Gruppen</em> (pp. 245–278) (Frankfurt/New York: Campus, 2012).

[39] See Malthaner and Hummel, “Islamistischer Terrorismus und salafistische Milieus” (see note 38 above).

[40] Martijn de Koning, “‘Kämpfen im Namen Allahs’: Transnationale soziale Felder und die Radikalisierung des Hofstad-Netzwerks in den Niederlanden,” in S. Malthaner and P. Waldmann (eds.). <em>Radikale</em> <em>Milieus: Das soziale Umfeld terroristischer Gruppen</em> (pp. 215–244) (Frankfurt/New York: Campus, 2012); Martijn de Koning and Roel Meijer, “Going all the way: Politicization and Radicalization of the Hofstad Network in the Netherlands,” in A. E. Azzi, X. Chryssochoou, B. Klandermans, B. Simon (eds.), <em>Identity and Participation in Culturally Diverse Societies: A Multidisciplinary Perspective</em> (pp. 220–238) (WileyBlackwell, 2011).

[41] Dierk Borstel and Wilhelm Heitmeyer, “Menschenfeindliche Mentalitäten, radikalisierte Milieus und Rechtsterrorismus,“ in S. Malthaner and P. Waldmann (eds.). <em>Radikale Milieus: Das soziale Umfeld terroristischer Gruppen</em> (pp. 339–368) (Frankfurt/New York: Campus, 2012).

[42] Luca Falciola, “Pathways of an ‘Early’ De-Escalation: the Case of the Weather Underground Organization,” paper presented at the ECPR General Conference, Sciences Po Bordeaux, 4–7 September 2013.

[43] See Malthaner, “Contextualizing Radicalization” (see note 37 above).

[44] Eamon Collins, <em>Killing Rage</em> (London: Granta, 1997), p. 295.

[45] John Darby, “Legitimate Targets: a Control on Violence?,” in A. Guelke (ed.), <em>New Perspectives on the Northern Ireland Conflict</em> (pp. 46–64) (Aldershot/Brookfield, 1994), p. 63.

[46] See Malthaner, “Mobilizing the Faithful” (see note 8 above).

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