If the minor operations of war were badly understood, strategy--the higher branch of the military art--was absolutely non-existent. An invading army moved into hostile territory, not in order to strike at some great strategical point, but merely to burn and harry the land. As no organized commissariat existed, the resources of even the richest districts were soon exhausted, and the invader moved off in search of subsistence, rather than for any higher aim. It is only towards the end of the period with which we are dealing that any traces of systematic arrangements for the provisioning of an army are found. Even these were for the most part the results of sheer necessity: in attacking a poor and uncultivated territory, like Wales or Scotland, the English kings found that they could not live on the country, and were compelled to take measures to keep their troops from starvation. But a French or German army, when it entered Flanders or Lombardy, or an English force in France, trusted, as all facts unite to demonstrate, for its maintenance to its power of plundering the invaded district[63]. Great battles were, on the whole, infrequent: a fact which appears strange, when the long-continued wars of the period are taken into consideration. Whole years of hostilities produced only a few partial skirmishes: compared with modern campaigns, the general engagements were incredibly few. Frederick the Great or Napoleon I. fought more battles in one year than a mediæval commander in ten. The fact would appear to be that the opposing armies, being guided by no very definite aims, and invariably neglecting to keep touch of each other by means of outposts and vedettes, might often miss each other altogether. When they met it was usually from the existence of some topographical necessity, of an old Roman road, or a ford or bridge on which all routes converged. Nothing could show the primitive state of the military art better than the fact that generals solemnly sent and accepted challenges to meet in battle at a given place and on a given day. Without such precautions there was apparently a danger lest the armies should lose sight of each other, and stray away in different directions. When maps were non-existent, and geographical knowledge both scanty and inaccurate, this was no inconceivable event. Even when two forces were actually in presence, it sometimes required more skill than the commanders owned to bring on a battle. Bela of Hungary and Ottokar of Bohemia were in arms in 1252, and both were equally bent on fighting; but when they sighted each other it was only to find that the River March was between them. To pass a stream in face of an enemy was a task far beyond the ability of a thirteenth-century general[64]-- as St. Louis had found, two years earlier, on the banks of the Achmoum Canal. Accordingly it was reckoned nothing strange when the Bohemian courteously invited his adversary either to cross the March