The Roman provinces of Africa, to which the Christian population was confined, never extended far southwards; the Sahara forms a barrier in this direction, so that the breadth of the coast seldom exceeds 80 or 100 miles. [348] Though there were as many as 500 bishoprics just before the Vandal conquest, this number can serve as no criterion of the number of the faithful, owing to the practice observed in the African Church of appointing bishops to the most inconsiderable towns and very frequently to the most obscure villages, [349] and it is doubtful whether Christianity ever spread far inland among the Berber tribes. [350] When the power of the Roman Empire declined in the fifth century, different tribes of this great race, known to the Romans under the names of Moors, Numidians, Libyans, etc., swarmed up from the south to ravage and destroy the wealthy cities of the coast. These invaders were certainly heathen. The Libyans, whose devastations are so pathetically bewailed by Synesius of Cyrene, pillaged and burnt the churches and carried off the sacred vessels for their own idolatrous rites, [351] and this province of Cyrenaica never recovered from their devastations, and Christianity was probably almost extinct here at the time of the Muslim invasion. The Moorish chieftain in the district of Tripolis, who was at war with the Vandal king Thorismund (496–524), but respected the churches and clergy of the orthodox, who had been ill-treated by the Vandals, declared his heathenism when he said, “I do not know who the God of the Christians is, but if he is so powerful as he is represented, he will take vengeance on those who insult him, and succour those who do him honour.” [352] There is some probability that the nomads of Mauritania also were very largely heathen.