The cause of the break with the tradition of antiquity was the rapid and unexpected advance of Islam. The result of this advance was the final separation of East from West, and the end of the Mediterranean unity.
Henri Pirenne
The Germanic invasions destroyed neither the Mediterranean unity of the ancient world, nor what may be regarded as the truly essential features of the Roman culture as it still existed in the 5th century, at a time when there was no longer an Emperor in the West.
The Germanic invasions in the West could not and did not in any way alter this state of affairs.
