Justinian’s Plague and the Birth of the Medieval World

By Andrew Latham

The Plague of Justinian, named after the Roman emperor who reigned from AD 527-65, arrived in Constantinople in AD 542, almost a year after the disease first made its appearance in the empire’s outer provinces. It continued to wash over the Mediterranean world in waves for another 225 years, finally disappearing in AD 755.

Although revisionist accounts dispute almost every element of the settled account of the plague, the generally accepted view is that it was the bubonic plague (Yersinia pestis), its distant origins probably lay in China, its proximate point of origin was Pelusium on the Nile River’s northern and eastern shores, and that it spread quickly from Egypt along the trade and military supply routes that crisscrossed the empire and connected it to the lands beyond, ultimately afflicting the entire Roman world and its peripheries. There is also general agreement that somewhere between 25% and 50% of the population of the empire died from the pandemic, totaling some 25-100 million people during its two centuries of recurrence.


Among the first-order knock-on effects of this culling of the population, two were particularly consequential. First, the loss of so many productive lives had a crippling impact on the economy. Second, this near-collapse of the empire’s economic base triggered a financial crisis of the imperial state.

Taken together, these two developments had the effect of fatally sapping the military strength of the empire. Lacking funds, the Romans were unable to recruit or retain troops. And lacking bodies, the Romans were simply unable to replace troops lost through combat or other forms of attrition. The convergence of these developments, coupled with a general plague-induced cultural enervation and eschatological resignation, resulted in an attenuated ability to either fight or bribe the empire’s enemies.

It was this fiscal-military crisis that ultimately brought the era of Western antiquity to a decisive end. Before the outbreak of the pandemic, emperor Justinian had been conducting a series of mostly successful military campaigns to reunify a Roman empire that had been sundered by waves of militarized migration from beyond its frontiers. With its debilitating effects on Roman finances and military power, the plague brought all of this to an end. Mainly because the black rat that carried the disease had not reached yet northern Europe, the barbarian tribes that had overrun the empire’s western provinces proved less susceptible to the disease than the peoples of the empire’s eastern remnant. They thus retained their military potential just as the empire was seeing its war-fighting capacity severely diminished.  The result was predictable. The Goths in Italy and the Vandals at Carthage reversed Justinian’s successes and irreversibly severed most of western Christendom from the empire.


The same was not true on the empire’s eastern frontier, where the forces of the Sasanian Empire proved every bit as susceptible to the plague as were those of Rome. As a result, both the Roman and Sasanian armies were laid low by the pandemic, and the two empires remained locked in the strategic stalemate that had defined the border between the two powers for decades.

As it turned out, though, it wasn’t the Sasanian empire that the Romans had to worry about on their eastern frontier. It was a new power, one that initially was not subject to the plague’s ravages.

Within a few years of the end of the Roman–Sasanian War of 602–628, the forces of the Islamic Rashidun Caliphate burst out of the Arabian Peninsula, swiftly conquering the entire Sasanian Empire and stripping the Roman Empire of its territories in the Levant, the Caucasus, Egypt, and North Africa. As a result, the Roman Empire was reduced to a rump territorial core consisting of Anatolia and a few islands and footholds in the Balkans and Italy.


In the aftermath of the Justinian plague, then, the basic contours of the medieval world were established. Before the plague, the Roman world had been a Mediterranean world, the Roman Empire, a Mediterranean superstate, and Greco-Roman culture, an artifact of the Mediterranean littoral’s great cities. The plague-induced defeats suffered by the empire on both its eastern and western frontiers changed all this. In place of the pre-pandemic Mediterranean world with its unified economic, political, religious, and cultural structures, there emerged three largely disarticulated and increasingly dissimilar civilizations: an Islamic one in the eastern and southern Mediterranean basin; a Greek one in what we now call Byzantium; and a “European” one in the western part of Christendom. It was this new European world order that provided the civilizational container within which what we have come to think of as the medieval world could evolve.

And what did this new European, medieval order look like? Well, most fundamentally, it was shaped by a religious sensibility that itself was molded by the experience of the plague. The level of eschatological anxiety induced by the pandemic within the empire simply cannot be overstated. People were not only terrified by the unprecedented and apparently random lethality of the disease; they feared that it might actually portend the end of the world.  In turn, this anxiety inclined people to turn to the established religion, which they hoped would both make meaningful and mitigate the horrors of the plague.

At one level, this plague-induced religiosity gave rise to works of public piety such as the construction of the Hagia Sophia in Constantinople. On another, it gave rise to new forms of popular piety, such as devotion to the Virgin Mary. And, of course, it birthed the Christian monastic movement, itself a religiously inflected effort to find a way to endure the social and cultural devastation visited by the pandemic. Before the plague, of course, the Roman world had been Christian. But after the plague, it was Christian in a decidedly medieval register. Put slightly differently, the plague transformed western Christianity, making it both distinctively European and peculiarly medieval.


Moreover, and still in a religious register, the plague-induced fracturing of the western empire left the institutional Church as the only translocal governance structure in the post-Roman West. In the aftermath of that fracturing, no single powerful secular government emerged to replace the structures of imperial rule. There was, however, a central ecclesiastical power that spanned the Latin Christian world, the Catholic Church. Filling the power vacuum created by the empire’s disintegration, the Church quickly rose to become the dominant power in medieval Europe. As temporal kingdoms eventually started to gain power, they naturally clashed – on both the battlefield of ideas and the actual battlefield – with the Church and with each other for supreme authority, both within and across individual kingdoms. More than anything else, it was this political dynamic that defined the geopolitics of medieval Europe.

Justinian’s Empire around the year 555. Map by Tataryn / Wikimedia Commons

Within this emerging European regional order, the plague also laid the foundations for a new and distinctively medieval socioeconomic system: feudalism. The Roman economy, of course, had been based on the institution of slavery. In such an economy, surplus is extracted directly from slaves who are owned by a lord and who work on his rural villa or manor. While there are often some free peasants in such a system, and even some who are owners of their own land or allod, the system as a whole is dependent on an abundant supply of chattel slaves. As the plague significantly diminished the supply of such labor between the fifth and eighth centuries, however, a new socioeconomic system evolved. Faced with shortages of slave labor to work their fields, landowners began to grant plots of land, called tenures, to nominally free laborers – called serfs – in exchange for tithes, service in the lord’s fields, and various other fees and taxes. In exchange, the lord provided military protection and justice for his tenants. Although serfs had no real status under the law, social custom and the competitive nature of the labor market prevented excessive exploitation. This agricultural production system, usually called “manorialism,” laid the foundations for the various forms of feudalism that were later to become the hallmark of medieval European life.

Finally, the Plague of Justinian resulted in a three-way clash of civilizations involving Islam, the rump Roman Empire, and Latin Christendom. To be sure, these were not three hermetically sealed containers.  People, goods, and ideas continued to move across the civilizational frontiers. But, as the continuing Islamic conquests, Latin Christian crusades, and occasional Byzantine efforts to retake parts of the empire attest, neither were they good neighbors. Fundamentally, they were geopolitical antagonists. And their geopolitical antagonisms were among the defining features of the medieval era.

Dr. Andrew Latham is a professor of political science at Macalester College in Saint Paul, Minnesota. He is the author, most recently, of a monograph entitled Medieval Sovereignty, to be published in 2020 by ARC Humanities Press. You can visit Andrew’s website at or follow Andrew on Twitter @aalatham


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Top Image: Map created by Anselmo Maria Banduri (1675-1743)



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