In the seventeenth century the art of war underwent a very quiet revolution. Although the weapons changed from the pike to the socket bayonet and the uniformed dress appeared on the battlefield, there was no 'birth of the modern army', but rather a gradual evolution of military techniques and the conduct of war. Improvements in the design of fortifications, prompted by advances in firearms technology, had subtle but far-reaching effects. Wars became longer and armies larger. The resulting cost required the princes and rulers of Europe to reform the administrative apparatus in order to better control their resources. Thus, while most armies remained mercenary formations, motivated by economic considerations rather than national allegiance, governments themselves started to become more absolute and more centralised. John Childs, one of the world's foremost historians of the period, charts this fascinating evolution in a concise and authoritative account.