By the end of the 4th century AD, the Roman Empire was divided into two distinct parts: east and west. Each was led by an emperor of its own. At times, the frontiers appeared disunited, especially on the Germanic frontier. The weaker of the two halves, the west, was dismembered in the course of the 5th century. The Visigoths established their own kingdom in Aquitaine in 418 AD and extended their power to Spain. The Vandals conquered parts of Spain and Gaul and later much of Africa by 439 AD. The Anglo-Saxons took over much of Roman Britain by establishing their own kingdom and changing the language. France came under the control of the Franks in the 5th century AD; in 507 AD, the Franks defeated the Visigoths at Vouillé to advance their borders to the Pyrenees. Italy became part of the Ostrogoth kingdom in 476 AD when Romulus Augustus was forced to abdicate.
The transition from Roman province to Germanic kingdom was a gradual one. The existing provincial aristocracies in many areas maintained control over land and power, only now under the rule of the Germanic elite. Christianity remained the dominant religion and bishops took on a more important role.
The Eastern Empire (now known as the Byzantine) was able to maintain and flourish under a series of capable emperors. Emperor Justinian was even able to regain some of the lost western provinces, notably North Africa (the Vandal kingdom fell in 533 AD), in the first half of the 6th century AD. The Eastern Empire was also able to retain Italy and Sicily for the next 200 years, as well as Spain. However, most of Italy did fall to the Lombards in 568 AD. The Slavs in the Balkans and the Arabs in the Near East and North Africa were able to gain much of the Byzantium territory. From that point, the empire was just one of several states maneuvering for power in the Mediterranean world of the early Middle Ages.