The combination of detailed historical analysis and recent developments in the theory of social networks can offer useful policy lessons with respect to contemporary terrorist movements

 New research on networks has put individual well connected agents at the centre of the spread of many social phenomena, including religious ideas.  England in the 1550s provides a model of how a society can be radicalized through heavy‐handed public persecution.  Much can be learnt from the spread of the medieval Cathar heresy by relatively few individuals, the ‘perfecti’. The inquisitors sent to suppress them used various unsuccessful strategies, whose failures can be illuminated by modern network theory.  Eventually the Inquisition was successful, by prioritizing the gaining of information about the movements of heretics and the isolating of local contacts.  The lessons for fighting religious terrorism are the premium on local intelligence and the importance of relying on the judgement of local communities to police themselves  Terrorist movements which promote martyrdom (e.g. suicide bombings) would have a much greater chance of influencing opinion in their favour if prominent individuals in the movement were the martyrs rather than the rank and file