This book addresses the interplay between radicalisation and political violence in Europe, as well as the effectiveness of counter-measures. As evidenced from the multitude of intercepted plots across several European cities since 2001, the threat level and the intensity of the desire to perpetrate mass-casualty attacks within Europe is not diminishing. While violent radicalization has gradually moved to the top of the EU counterterrorism agenda, it has been accompanied by a relatively embryonic understanding about the processes and interplay of factors that contribute to radicalization, which are played out differently in cities like Paris, Rome, London and Copenhagen. Undoubtedly, there are common factors at the global and regional levels that facilitate radicalization, but it is also clear that radicalization is very context dependent. This book provides crucial insights into different ways to understand violent radicalization within national contexts and the challenges addressing the many pathways into terrorism inspired by al-Qaeda and other forms of Islamic extremism.