The problem of dealing with the ongoing and constantly evolving threat of terrorism is something which continues to preoccupy governments worldwide. Has sufficient attention been paid to what happens with terrorist organizations after they change leaders? Has enough research been done on how and in what manner they are changed/replaced? This book is a collection of follow-up papers from experts who participated in the NATO Advanced Research Workshop (ARW) entitled The Perseverance of Terrorism: Focus on Leaders, held in 2013, and is the third in a series of outputs related to the approach to terrorist leadership. These papers are presented with the aim of further elaborating the challenges of contemporary terrorism and enriching the existing academic debate. The first two papers concentrate on how better to understand, define and analyze terrorism. The next two authors examine the relevance of contemporary terrorism, its approach and its significance as prevailing threat. The core of the debate is structured around the issue of terrorist leadership, and the majority of authors have explored this phenomenon. Seven different approaches are presented which demonstrate the importance of leadership for terrorist organizations. This book will serve as a guidebook on several terrorism-related issues which trigger academic debate, and which must be taken into account by practitioners in their efforts to design appropriate counter-terrorist measures.