Terrorism is an age-old problem and takes many forms. In Western Europe in the first years of the twenty-first century, for example, the terrorist threat has come primarily from fundamentalist Islamist, or, as they are also called, Islamic fundamentalist groups. We have also seen destruction and violence perpetrated by right-wing extremists. Naturally, such activities need to be countered. And for the response to be effective, it is essential that we understand terrorism and the associated processes of radicalization. This book is an attempt to add to the body of knowledge in that field.