Abstract
Recently, scholars, policy-makers and experts have applied the term cumulative extremism to describe an escalating conflict between radical Islamist and anti-Islamist groups in Britain. This thesis aims at reaching a more nuanced understanding of the interactions between the two adversary groups, identifying the underlying processes that drive the relationship. I propose an alternative concept to cumulative extremism that I have coined Reciprocal Intergroup Radicalisation (RIR) that I argue better captures the interactions between the adversary groups. The research question asks which mechanisms fuel or contain reciprocal intergroup radicalisation (RIR), and what conditions facilitate or obstruct these mechanisms from unfolding. Drawing from the social movement literature, I have developed a theoretical framework consisting of six mechanisms that either fuel or contain radicalisation of interactions between anti-Islamists and radical Islamists. I have combined a comparative analysis with process tracing, with Britain serving as a positive case and Norway as a negative case. Similar anti-Islamist and radical Islamist social movement organisations emerged around the same time in Britain and Norway, yet no violent interactions occurred in the latter case. The aim is therefore to understand this discrepancy. I collected a wide-ranging source material through document analysis and combined these sources with four semi-structured expert interviews. In the analysis, I demonstrate that the level of RIR is conditioned by a number of mechanisms that all interact together. I found that the level of repression, the absence of a radical right party, organisational strength, the organisations’ enemy images, and the narrative of the media all impact RIR to some extent. These findings have important implications for how law enforcement, the media, and policy-makers should approach the two opposing groups in order to avoid counter-productive measures that fuel rather than contain the conflict.