In exploring how the Christian religion became such a defining feature of the European landscape, and how a small sect of isolated congregations was transformed into a mass movement centrally directed from Rome, Heather shows how Christendom constantly battled against both so-called 'heresies' and other forms of belief. From the crisis that followed the collapse of the Roman Empire, which left the religion teetering on the edge of extinction, to the astonishing revolution in which the Papacy emerged as the head of a vast international corporation, Heather traces Christendom's chameleon-like capacity for self-reinvention and willingness to mobilize well-directed force. This is its extraordinary story.