We propose an explanatory framework for the comparative study of radicalization that focuses on its “how” and “when” questions. We build on the relational tradition in the study of social movements and contentious politics by expanding on a mechanism-process research strategy. Attentive to similarities as well as to dissimilarities, our comparative framework traces processes of radicalization by delineating four key arenas of interaction— between movement and political environment, among movement actors, between movement activists and state security forces, and between the movement and a countermovement. Then, we analyze how four similar corresponding general mechanisms—opportunity/threat spirals, competition for power, outbidding, and object shift—combine differently to drive the process. Last, we identify a set of submechanisms for each general mechanism. The explanatory utility of our framework is demonstrated through the analysis of three ethnonational episodes of radicalization: the enosis-EOKA movement in Cyprus (1950-1959), the Provisional Irish Republican Army in Northern Ireland (1969-1972), and the Fatah-Tanzim in Palestine (1995-2001)
