He begins by analysing the sources for our knowledge of the military history of the period, assessing their reliability: some chroniclers exaggerate, others are careful observers or have access to official records. There follows an examination of the constituent parts of the medieval army, knights and footsoldiers, equipment and terms of service, behaviour on the field, and psychology, before the problematic question of medieval tactics is addressed through analysis of accounts of a series of major battles. Strategy is discussed in the context of these battles: whether to seek battle, fight a defensive war, or attempt a war of conquest.

The Art of War has been very simply defined as 'the art which enables any commander to worst the forces opposed to him.' It is therefore conversant with an enormous variety of subjects: Strategy and Tactics are but two of the more important of its branches. Besides dealing with discipline, organization, and armament, it is bound to investigate every means which can be adapted to increase the physical or moral efficiency of an army. Contents: The Transition from Roman to Mediæval Forms in War - A.D. 378–582. The Early Middle Ages - A.D. 476–1066–81. The Byzantines and their Enemies - A.D. 582–1071. The Supremacy of Feudal Cavalry - A.D. 1066–1346. The Swiss - A.D. 1315–1515. The English and their Enemies - A.D. 1272–1485.