We have seen in the first chapter that the Middle Ages were politically decentralized to a high degree, but that, on the other hand, they had a strong sense of moral unity. Christendom was one big family. Mediæval warfare was conditioned by these two political factors. On account of decentralization in all its forms, the central governments had only a slight power to compel the entire body of their nominal subjects to move, irrespective of the individual wills of those subjects with regard to the particular matter in dispute; slight, that is, compared with the power of modern governments. On account both of decentralization and also of the moral unity of Christendom, wars between Christian men in the Middle Ages seldom involved any great point of principle. There could be no opposition between different and mutually exclusive types of civilization, as between the French and German types to-day. Usually the dispute concerned merely the opposing claims of two parties to ownership of, and therefore feudal administration over, a patch of land. Accordingly campaigns were apt to be short and inconclusive, and warfare in general somewhat of an adventurous sport. It is true that in the thirteenth century, a time still simple, war had not yet taken on the unreality of aim and the elaborate trappings which are the mark of the later Middle Ages. Already, however, it had become something of a “gentleman’s game,” as were the dynastic wars of the eighteenth century. Naturally, therefore, when a vital principle was involved (as in the Crusade which we are about to study), operations were always tending to relapse into the haphazard fashion fostered by the contemporary idea of war as an affair in which nothing of great moment to society as a whole was at stake. As far as the technique of operations is concerned, the important features are mail-clad cavalry and permanent fortification. Axiomatically, infantry is worth more than cavalry in combats between disciplined bodies of troops, but less than cavalry in raids and in defence against raids, as in our own Indian wars, and in the Boer War. Thus, in late Roman times and the Dark Ages, cavalry gradually became preponderant over infantry, throughout the greater part of Europe. The Franks who ended by setting up their chieftain as successor to the Western Emperors, were an exception. It was not until the great Viking harry of the ninth century, in which our tradition almost went under, that the defenders of “Francia” began to rely mainly upon cavalry. That arm alone was fast enough to overtake the pirates whose first act on landing was to steal horses for themselves. And it was in the repulse of the Viking, as we have seen, that mediæval society crystallized.