when a series of barbarian peoples invaded the Mediterranean world .... And who WERE these barbarians, exactly, hmmmm? Maybe, Ohhhhh, maybe...MOE-HAM-HEADS? (Best Church Lady imitation)
Um... most of them invaded the Mediterranean world before the birth of Mohammed. They were generally various German and Scandinavian tribes, such as the Franks, Marcomanni, Burgundians, Ostrogoths, Vandals, Visigoths, etc. Many of these, such as the Goths, were Christian, of what is now considered the Arian or Semi-Arian heresies.