Ever since the beginning of the fifth century A. D. Roman possessions in Europe were being flooded by the advance of the Vandals. In 428 the terrible Genesric crossed to Africa from Spain, with an army of ninety thousand men, and landed at Ceuta. Like all new invaders, he was welcomed as a savior, and his success was instantaneous. He swept the Roman armies before him, he built a fleet and became the terror of the Mediterranean, and in 455 took Rome. How far these conquests would have continued it is difficult to say had not Genesric died. With his death his followers, who had drifted into an easy-going state, no longer held together, but became the prey of jealous strifes among chiefs. Their fall was rapid. The Roman Government, now transferred to Constantinople, was awaiting the opportunity to avenge its defeat. A little more than a hundred years after the landing of the Vandals in Africa, Belisarius sailed from Constantinople with six hundred ships, and three months later landed in Tripoli. The Byzantine invasion had begun, and in three months Belisarius was able to announce to the Emperor Justinian that North Africa was again part of the Roman Empire. But the Byzantine rule did not last long. The country was rent by wars and revolts; the people were worn out with changes of government; and, though there remain great forts and mightily walled cities as a record of this rule, they are evidence in themselves of the turbulent times which shook the country. When, therefore, the first Arab invasion poured in, there was nothing to quell it, and for one last time Imperial Rome struggled for a moment, staggered and fell. The first Arab invasion of the seventh century was more a series of raids than anything else. Mohammed had appeared and died, but his teaching had remained, and had inspired those bands of wild nomads to organize themselves. Persia, Syria, Egypt had fallen before the advance, and soon they began moving farther west. The most important of these raids was that led by Sidi Okba, who traversed the whole of Algeria and Morocco, and who, no doubt, would have gone on had he not been arrested by the Atlantic. He was killed during his return journey by the Berber army under Koceila, and he is buried near Biskra, where his memory is venerated. Hassan followed him, and finally drove the last Byzantines out of North Africa. Needless to say, the chief object of the invaders had been to convert the people to the new faith, and little by little the Berbers became Mohammedans. It did not take long for them to create dissension in these beliefs, but they remained generally under the law of the Prophet, respecting the principles even more rigidly than their conquerors.