From 12th-century Italy to today, by way of Columbus, Newton, the British Israelites and the Aryan Nation, the tradition of messianic revolution has formed a major undercurrent in Western history. All are united in their fixation on the countdown to Armageddon and plans to hasten Christ's Second Coming. From the Great Disappointment (when the world failed to end in 1844) were born the Jehovah's Witnesses and Seventh-Day Adventists, assorted white supremacists, and eventually the movement which led to mass suicide in Jonestown and the Oklahoma City bombing. In our time mainstream fundamentalists - even US President Ronald Reagan -have eagerly expected the End of Days, often envisaged as a nuclear holocaust. Such beliefs may seem terrifying or just absurd, but they are not going to go away. This incisive historical analysis provides the essential tools for understanding and combatting them.