Henri Pirenne, Mohammed and Charlemagne (Mahomet et Charlemagne). First published Brussels: Nouvelle Société d'Éditions, 1937. Translated by Bernard Miall. This text is in the public domain. Pirenne's central claim: the Germanic kingdoms of the fifth and sixth centuries preserved Roman civilization around the Mediterranean basin. What severed antiquity from the Middle Ages was not Odoacer's deposition of Romulus Augustulus in 476, but the Islamic expansion of the seventh and eighth centuries, which cut the sea lanes, strangled the commerce that had knit the Mediterranean world together, and forced western Europe inward — creating the land-locked, self-sufficient Carolingian economy. "Without Islam, the Frankish Empire would probably never have existed, and Charlemagne, without Mahomet, would be inconceivable."

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Mohammed and Charlemagne

Henri Pirenne

Henri Pirenne (1862–1935) spent part of the First World War interned as a German prisoner, and it was in captivity — without access to books or libraries — that he worked out the thesis that would reshape medieval historiography. Mohammed and Charlemagne, completed in the final years of his life and published posthumously in 1937, is the culmination of a career spent questioning received periodizations and looking beneath political events for the economic and social structures that determined the longue durée.

The Pirenne Thesis has been contested, refined, and partially rehabilitated by subsequent archaeology — ceramic evidence, coin finds, and pollen analysis have both complicated and, in places, supported his picture of Mediterranean disruption. Whatever its limits as a finished argument, it remains one of the most generative hypotheses in the discipline: the starting point for any serious engagement with how antiquity became the Middle Ages, and a model of how economic history and political history can be made to illuminate each other.