But, before we give any account of the revolutions which took place among the already existing powers of Western Europe, it will be well to describe the geographical changes which were caused by the appearance of absolutely new actors on two sides of the Empire. ♦Roman province in Spain recovered by the Goths. 534-572.♦ One point however may be noticed here, as standing apart from the general course of events, namely, that the Roman province in Spain was won gradually back by the West-Goths. ♦616-624.♦ The inland cities, as Cordova, were hardly kept forty years, and the whole of the Imperial possessions in Spain were lost during the reign of Heraclius. Thus the great dominion which Justinian had won back in the West, important as were its historical results, was itself of very short duration; a large part of Italy was lost almost as soon as it was won, and the recovered dominion in Spain did not abide more than ninety years. But meanwhile, in the course of the seventh century, nations which had hitherto been unknown or unimportant began to play a great part in history and greatly to change the face of the map. These new powers fall under two heads; those who appeared on the northern and those who appeared on the eastern frontier of the Empire. The nations who appeared on the North were, like the early Teutonic invaders of the Empire, ready to act, if partly as conquerors, partly also as disciples; those who appeared on the East were the champions of an utterly different system in religion and everything else. In short, the old rivalry of the East and West now takes a distinctly aggressive form on the part of the East. ♦Wars between Rome and Persia.♦ As long as the Sassanid dynasty lasted, Rome and Persia still continued their old rivalry on nearly equal terms. The long wars between the two Empires made little difference in their boundaries. ♦Wars of Chosroes and Heraclius, 603-628.♦ In the last stage of their warfare Chosroes took Jerusalem and Antioch, and encamped at Chalkêdôn. Heraclius pressed his eastern victories beyond the boundaries of the Empire under Trajan. But even these great campaigns made no lasting difference in the map, except so far as, by weakening Rome and Persia alike, they paved the way for the greatest change of all. ♦Extension of the Roman power on the Euxine.♦ More important to geography was a change which took place at somewhat earlier time when, during the reign of Justinian, the Roman power was extended on the Eastern side of the Euxine in _Colchis_ or _Lazica_. ♦The Arabian vassals of Rome and Persia.♦ The southern borders of each Empire were to some extent protected by the dominion of dependent Arabian kings, the _Ghassanides_ being vassals of Rome, and the _Lachmites_ to the east of them being vassals of Persia. But a change came presently which altogether overthrew the Persian kingdom, which deprived the Roman Empire of its Eastern, Egyptian, and African