The period of a little more than two centuries after the downfall of the caliphate was marked by a complete change from that preceding it, and in like manner was quite independent of the next succeeding era. Up to this time Moslem Spain had represented by far the principal element in the peninsula. The Christian states had maintained themselves with difficulty, making occasional gains, which were not infrequently followed by equally great losses whenever the Moslem power was sufficiently united internally to present its full strength. The civilization of the Christian kingdoms had also been notably inferior in almost every respect to that of the Moslem south. From the eleventh to the middle of the thirteenth century, however, the region of Moslem Spain, divided against itself, could not make an effective resistance, and the Christian powers began an offensive which enabled them to reconquer all of the peninsula except for a narrow strip in southern Andalusia. These wars partook very largely of the crusading spirit then so prevalent in Europe, and although it was not nearly so persistent, fervid, or exclusive an aim as is usually believed it seems appropriate to characterize this era as that of the Spanish crusades. This was also a period of noteworthy advance in internal organization in Christian Spain, for although civil war and disorder were great as compared with some later eras many regions enjoyed long terms of peace, very much more complete at least than in the three preceding centuries. The pushing back of the Moslem frontier conduced greatly to this end. The kings gradually became more powerful than the great individual nobles, who had been able to meet them on virtually equal terms before. The free commoners advanced both in status and in numbers. In material well-being there was a marked improvement. Finally, in general culture the same tendency appeared. In all of these respects the fund of civilization was very slight compared with what it was to become in succeeding centuries, but it was at least something, whereas the period before had represented little more than bare existence. Despite the fact that there was very little understanding of the ideal of national unity, as evidenced by the frequency with which monarchs divided their kingdoms, circumstances tended toward the accomplishment of what men could not readily grasp. Two great states emerged in Christian Spain, the kingdoms of Castile and Aragon. They were able even to act in peace and concert at times in the wars against the Moslems. A third region tended to withdraw from the current of peninsula unity, for it was in this period that the modern state of Portugal had its independent beginnings. Nevertheless, Moslem Spain, though less important than Castile and Aragon, remained the keynote of the period, not alone because of the wars against it, but also because its civilization, especially in material and intellectual