Contributor(s): Professor Peter Neumann | Large numbers of foreigners, including many Europeans, have joined jihadist groups in the Syrian/Iraqi conflict. Who are these people, why do they go, and what - if any - threat will they pose upon their return? Drawing on a large database with hundreds of social media profiles of Western fighters, dozens of interviews, and fieldwork, Professor Peter Neumann of King's College London's International Centre for the Study of Radicalisation will talk about the fighters' motivations and consequences.