Hand pushing against police riot shields

The internal brakes on violent escalation



Total value of project


Project team

Dr Joel Busher


Donald Holbrook, University College London; Graham Macklin, Center for Research on Extremism, Oslo University

Duration of project

2017 - 2019

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Project overview

Why do some ‘extremists’ or ‘extremist groups’ choose not to engage in violence, or only in particular forms of low-level violence? Why, even in deeply violent groups, are there often thresholds of violence that members rarely if ever cross?

Part of the answer is likely to lie in external constraints, such as the counter-measures put in place by state and non-state actors to inhibit the activities of such groups. Yet the fact that few if any groups carry out as much violence as they are capable of, indicates that in most cases external constraints comprise only part of the answer. Detailed empirical accounts indicate that pressures within these groups also inhibit the adoption or diffusion of greater violence. In other words, the limits on violence are to some extent self-imposed. To date, however, there has been little systematic analysis of these ‘internal brakes’ on violent escalation.

In response to this gap in understanding, we set out to develop a typology to describe and categorise the internal brakes on violent escalation within extremist groups – including both more and less formalised groups. 

Project objectives

To develop a descriptive typology of the ‘internal brakes’ on violent escalation – the practices through which members of militant groups themselves contribute to limit their use of violence.

  • This project and the typology that it developed offers an important new perspective on the action repertoires of militant or ‘extremist’ groups. It has already inspired a special issue of Perspectives on Terrorism that further interrogates these mechanisms, and has stimulated substantial interest internationally.

    The typology has had a significant impact on policy and practice, informing risk assessment and decision making within the UK intelligence and security communities. It has also informed international training programmes through the International Security Sector Advisory Team (ISSAT).

  • See the project website for reports. 

    Additional academic publications

    Publications directly from the project:

    Busher, J., Holbrook, D. & Macklin, G. (2021) How the “Internal Brakes” on Violent Escalation Work and Fail: Toward a Conceptual Framework for Understanding Intra-Group Processes of Restraint in Militant Groups. Studies in Conflict & Terrorism. 

    Busher, J., Holbrook, D. & Macklin, G. (2019) The Internal Brakes on Violent Escalation: A Typology.  Behavioural Science of Terrorism and Political Aggression, 11(1), 3-25.

    Inspired by and following on from the project:

    Perpsectives on Terrorism. ‘Restraint in Terrorist Groups and Radical Milieus’, December 2020, edited by J. Busher & T. Bjørgo.

    Busher, J. & Bjørgo, T. (2020) Restraint in Terrorist Groups and Radical Milieus: Towards a Research Agenda. Perspectives on Terrorism, 14(6), 2-13.

    Ellefsen, R. & Busher, J. (2020) The Dynamics of Restraint in the Stop Huntingdon Animal Cruelty Campaign. Perspectives on Terrorism, 14(6), 165-179.

    Macklin, G. (2020) The Internal Brakes on Violent Escalation within the British Extreme Right in the 1990s. Perspectives on Terrorism, 14(6), 49-64.

    Holbrook, D. (2020) Internal Debates, Doubts and Discussions on the Scope of Jihadi Violence: The Case of the Turnup Terror Squad. Perspectives on Terrorism, 14(6), 77-90.

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University of the year shortlisted
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