During the past 2 decades, two interrelated security threats have emerged that Western democracies will likely be forced to contend with for the foreseeable future. The first of these threats is multifaceted inasmuch as it stems from a complex combination of religious, political, historical, cultural, social, and economic motivational factors: the growing predilection for carrying out mass casualty terrorist attacks inside the territories of "infidel" Western countries by clandestine operational cells that are inspired ideologically by, and sometimes linked organizationally to, various jihadist networks with a global agenda. The most important of these latter networks is still the late Usama bin Ladin's high-profile group Qa'idat al-Jihad (The Base [or Foundation] of the Jihad), together with its many organizational offshoots and regional affiliates. The second threat is more narrowly technical: the widespread fabrication of increasingly sophisticated and destructive improvised explosive devices (IEDs) by those very same jihadist groups, devices which- if properly constructed-are capable of causing extensive human casualties and significant amounts of physical destruction within their respective blast radiuses. The purpose of this book is to examine these dual intersecting threats within the recent European context in an effort to assess what they might portend for the future, including the U.S. homeland.