The terrorist attacks in Madrid in March 2004 and in London in July 2005, the assassination of Dutch filmmaker Theo Van Gogh in November 2004, the killing of U.S. soldiers at Frankfurt airport in March 2011, and several major foiled attacks throughout Europe such as the so-called Europlot – al-Qaeda’s plan, uncovered in 2010, to attack targets in several European countries – erased any doubt that Europe has become a central theater of Islamist terrorist operations. The 9/11 Commission listed European cities with Muslim communities, along with the Afghan-Pakistani border, the Horn of Africa, and Southeast Asia, among the places where terrorists seek sanctuary and operating bases. Indeed, investigations after 9/11 uncovered extensive terrorist networks in the United Kingdom, France, Spain, Germany, Belgium, and Italy. The threat of Islamic radicalism has also become a central contentious issue of domestic and European politics, influencing elections and policy at all levels from the municipal to the European Union.

To understand the shape and dynamics of the Islamist extremist and terrorist challenge in Europe, it is necessary to examine the sources of Islamist radicalization in Europe; jihadist ideology and strategy; radicalization patterns, nodes, and networks; terrorist operations and tactics; and the response of European governments and societies. We can then draw the implications and lessons from the European experience with Islamist extremism and terrorism.