In the 1920s, a Belgian historian, Henri Pirenne, challenged the commonly accepted notion that the end of the Western Roman Empire around 500C.E. signaled a catastrophic collapse of Roman civilization itself. The Pirenne Thesis claimed that Roman civilization continued until the Muslim Arabs broke up the unity of the Mediterranean in the seventh century. Elements of the Pirenne thesis have come under attack since then, although historians have learned to take a more balanced look at the fall of Rome and the start of the Middle Ages thanks to Pirenne.
Archaeological evidence has provided an interesting twist to the link between the Arab Muslims and the Frankish dynasty of the Carolingians, but in the eight and ninth centuries rather than the seventh. It starts at the height of the Arabs’ power when they were carrying on trade as far away as India, Central Asia, North Africa, Spain, and also present day Russia, where they would exchange silver for furs and amber. Viking merchants from Russia would then sail by way of the Baltic Sea to the Franks’ realm and trade Muslim silver for Frankish goods. Archaeologists have found evidence of a good deal of this silver in the Frankish realm, which would go a long way toward explaining the sudden resurgence of the Franks in the 700s, and early 800s, and in particular their cultural activities: trying to revive learning, copying ancient Roman manuscripts, and building projects such as Charlemagne’s cathedral at Aachen.
Unfortunately, just as Muslim silver from Baghdad helped make Frankish power and prosperity possible, the lack of it helped bring down Charlemagne’s successors. The reason was apparently too much spending by the caliphs on building projects. When, for whatever reasons, their money ran out, and so did trade up into Russia, thus cutting off the Franks’ source of silver and much of their power. Then everything started going wrong.
When Arab traders in the Mediterranean and Vikings in the Baltic and North Seas saw their trade drying up, they turned to raiding to supplement their incomes. This, of course, was destructive to the overall economy, thus weakening the Franks’ ability to trade and marshal the resources necessary, thus allowing more Arab and Viking raids, and so on. By 900, the Frankish empire had disintegrated into various pieces, leaving the way for new powers and institutions to take over.