For decades, a new type of terrorism has been quietly gathering ranks in the world. America's ability to remain oblivious to these new movements ended on September 11, 2001. The Islamist fanatics in the global Salafi jihad (the violent, revivalist social movement of which al Qaeda is a part) target the West, but their operations mercilessly slaughter thousands of people of all races and religions throughout the world. Marc Sageman challenges conventional wisdom about terrorism, observing that the key to mounting an effective defense against future attacks is a thorough understanding of the...

In the post-September 11 world, Al Qaeda is no longer the central organizing force that aids or authorizes terrorist attacks or recruits terrorists. It is now more a source of inspiration for terrorist acts carried out by independent local groups that have branded themselves with the Al Qaeda name. Building on his previous groundbreaking work on the Al Qaeda network, forensic psychiatrist Marc Sageman has greatly expanded his research to explain how Islamic terrorism emerges and operates in the twenty-first century.

In "Leaderless Jihad," Sageman rejects the views that place...

As Islamist terrorism has ravaged the contemporary Middle East and led to sporadic attacks in Europe and the United States, countless journalists, pundits, and politicians have turned their attention to the question of what motivates those who commit violence in the name of political beliefs. Terrorism is not solely the preserve of Islam, however, nor is it a new phenomenon. It emerges from social processes and conditions common to societies throughout modern history, and the story of its origins spans centuries, encompassing numerous radical and revolutionary movements.

Marc Sageman...