The first ever sustained enquiry into one of the fundamental questions about terrorism: does it work? And if so, then how? Written by one of the world´s foremost experts on terrorism, with over thirty years´ experience analysing the field. Focuses on four of the most significant terrorist organizations of the last fifty years: al-Qaida, the Provisional IRA, Hamas, and ETA. Uses a wealth of interview material collected over the years, both with former terrorists and their enemies in the counter-intelligence, police, and security services. Argues that we need a far more honest understanding of the degree to which terrorism works - and the precise ways in which it does so.