​This book provides a new military history of Byzantine emperor Alexios I Komnenos's campaigns in the Balkans, during the first fourteen years of his rule. While the tactics and manoeuvres Alexios used against Robert Guiscard's Normans are relatively well-known, his strategy in dealing with Pecheneg and Cuman adversaries in the region has received less attention in historical scholarship. This book provides a much-need synthesis of these three closely linked campaigns – often treated as discrete events – revealing a surprising coherence in Alexios' response, and explores the position of Byzantium's army and navy on the eve of the First Crusade.