Few attempts had been made to define "the crusade" before the first edition of this book was published in 1977. Since then, a number of historians have built on Jonathan Riley-Smith's conclusions. Their research has been incorporated into this revised, third edition of a classic starting point for any study of the crusading movement. Among other key aspects, the book deals with causes for crusading, the legitimising authority of the papacy, recruitment, and the nature of the crusade vow and its consequences. This new edition also features a useful chronology and brief biographies of some crusaders, both real and imaginary.