BUT in the development of classes, warfare as well as economics plays a part. To the adventurous or the able, both the Church and the army offered careers from which they might graduate to the king's service. War, never so chivalrous as in the tales about Richard Lionheart, for example, became professional. To the baron war was still an adventure or a foray; to the king and to the nation it became a business of politics and economics. To carry on a political war on the old feudal system was impossible. Service was limited by tradition and was rapidly becoming still more limited as opportunity occurred to escape it. The practice arose of hiring the vassals of a noble, of trusting the king's servants to recruit, of levying not by head but by district for defence.
Here is the nucleus of the king's army, the standing army of which the English by tradition are so whole-heartedly suspicious. Thus Edward I., attended by hardly any of his nobles, could maintain forces in the field all winter and pay and feed them himself. The test of the new system came with the war with Scotland. The issue was framed feudallyWas Scotland a fief of the English crown? Actually, the determining factor was Edward's political prescience in seeing the desirability, indeed the necessity, from the point of view of English policy, that there should be only one realm in Britain. The claimants to the vacant throne of Scotland were all connected with the Scottish royal house, but most of them were also English nobles. They accepted Edward's interpretation of the law, and John de Baliol donned the Scottish crown as Edward's vassal (1292). A true feudalist, he rebelled on the first opportunity, and was promptly and mercilessly crushed and deposed. Scotland became an English territory (1296).