In Spain, the Gothic supremacy gave promise of an orderly and just government. In the wide realms of the Franks anarchy and bloodshed were almost ceaseless. In neither did the dominant Teutons drive out the older Iberian and Celtic populations, as the English were doing in the open lands of the northern island. In both, the German institutions were developing into that feudal system which was utterly incompatible with the maintenance of a strong central rule, since it enabled a powerful vassal to bid defiance to his nominal suzerain. Throughout the sixth and seventh centuries progress was stayed in ancient Gaul; in Spain it was to be revolutionised by a new invader. [Sidenote: Islam in Being] Eastward, at the end of the sixth century, the Slavonic wave was surging upon the empire’s northern frontier; in Asia, Persia was again forcing her way towards the Mediterranean. Both were checked by the Emperor Heraclius early in the seventh century. But, meantime, a new Power had come into being. Mohammed had arisen. Inspired by the fanatical fervour of Islam, the warriors of Arabia, soon to be known as the Saracens, swept all before them. They did not at first make Europe their objective; the Caliphs carried their conquering arms over Western Asia, into Egypt, and along the southern coasts of the Mediterranean. Then they began to beat against the empire itself. The eighth century had hardly opened when they poured into Spain; dissensions among the Gothic chiefs gave them prompt victory. They swept up to the Pyrenees; but their advance was stayed by Charles Martel, the virtual lord of the Frankish kingdom. On the East their armies assailed Constantinople, but were disastrously repulsed by the Emperor Leo the Isaurian. Now, for the first time, Papal sanction was demanded and obtained for a change of dynasty. The last Merovingian king of the Franks was deposed in favour of Pepin, the son of Charles Martel. He was succeeded by his son, Karl, a German of the Germans, despite the French form of his popular title Charlemagne. [Sidenote: Charlemagne and His Empire] During his long reign the Moors in Spain were driven back beyond the Ebro; the Saxon tribes across the Rhine were forced to submit and to accept Christianity; the Lombard oppressors of Italy were vanquished; and on the Pope’s initiative, Charlemagne himself was acclaimed and crowned at Rome as emperor and successor of the Cæsars. All of the West that remained to Byzantium was Southern Italy. The revived empire came into being on Christmas Day, A.D. 800.