Byzantine Culture

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The Plague of Justinian

The bubonic plague that struck the Byzantine Empire in 541, killed a large share of its population, and returned for two centuries — its course, its evidence, and its disputed consequences.

In the summer of 541 an epidemic reached the Egyptian port of Pelusium, at the eastern edge of the Nile delta. By the spring of 542 it was in Constantinople, and over the following four months it killed a substantial fraction of the population of the largest city in the Mediterranean world. It then spread along every shipping route and road in the Roman, Persian and post-Roman world, reaching Ireland and Arabia, and returned in waves roughly every eleven to fifteen years until the middle of the eighth century.

This was the first of the three great plague pandemics of recorded history — the second being the Black Death of the fourteenth century, the third the outbreak that began in Yunnan in the 1850s. The pathogen has been identified: DNA from Yersinia pestis has been recovered from sixth-century burials at Aschheim in Bavaria and at other sites, and the strain has been sequenced. That settles a question debated for a century and a half; almost everything else about the pandemic’s scale and consequences remains contested.

The Contemporary Account

Procopius of Caesarea, who was in Constantinople during the outbreak of 542, wrote the fullest description, in a chapter of the Persian War consciously modelled on Thucydides on the plague of Athens. Modelling the passage on a literary predecessor did not prevent him from observing accurately. He describes the onset — a sudden mild fever, then within a day or two a swelling in the groin, the armpit, beside the ear or on the thigh — which is a clinically recognisable account of bubonic plague. He notes that some patients fell into coma, others into violent delirium; that those who developed black blisters died within a day; that vomiting blood was invariably fatal; and that the disease did not discriminate by habit of life, age or constitution.

He also describes the collapse of civic order. Burial arrangements failed; the roofs of the towers of the fortress at Sycae across the Golden Horn were taken off and the towers filled with bodies, so that, in his words, an evil stench blew across the city. The emperor appointed an official, Theodore, to organise the disposal of the dead and paid for it from the treasury.

His figure — ten thousand deaths a day at the peak — is not usable as a statistic. John of Ephesus, a Syriac writer who travelled through the affected provinces and reached Constantinople during the epidemic, gives comparable impressions and comparable arithmetic. The honest summary is that both men witnessed a mortality event without precedent in their experience and reached for the largest numbers they could imagine.

Justinian himself caught the disease and recovered, which is well attested; Procopius, who loathed him, notes it without comment in the public history and makes much of it in the Secret History.

How It Spread

The plague reservoir is rodent-borne, transmitted by fleas, and the routes of the first pandemic follow the grain trade with some precision: Egypt to Constantinople, Constantinople to the Aegean and the Levant, the ports of Italy, Gaul, Spain and North Africa, and inland along rivers. Gregory of Tours records outbreaks in Gaul; Bede records the epidemic of 664 in Britain and Ireland; Arabic sources record the plague of ‘Amwas in Syria in 638–639, which killed a number of prominent companions of the Prophet.

Recurrence was the distinguishing feature. Modern lists count something like eighteen waves between 541 and 750. A city might be struck once a generation, which meant that each outbreak found a population with no surviving immunity in its younger cohorts.

The Argument About Consequences

For much of the twentieth century the plague was treated as a decisive cause of the transformation of the ancient world: it was said to have wrecked Justinian’s reconquest of the west, emptied the countryside, shrunk the cities, crippled tax revenue, and left both Rome and Persia unable to resist the Arab conquests a century later.

That maximalist case has been challenged hard in the last two decades, and the debate is genuinely unresolved. The sceptical position argues that:

  • The written sources are concentrated in a few cities and a few authors with literary reasons for exaggeration.
  • Archaeological indicators of settlement contraction in many regions begin before 541 or after 600, not in the 540s.
  • Egyptian papyri, which record rents, wages and land transactions in detail, do not show the labour shortage and wage spike that a catastrophic mortality should produce.
  • Mass graves attributable to the pandemic are few compared with those of the Black Death.

The maximalist reply is that the absence of evidence in a period with thin documentation proves little, that DNA from widely separated sites shows genuine geographical reach, and that the sixth-century sources, for all their rhetoric, are describing something they had no template for.

Where the two sides broadly agree is that the pandemic was real, serious, and recurrent, and that its effects were uneven — severe in ports and cities, patchy inland.

What Can Be Said with Confidence

The state’s revenue was disrupted. Justinian’s legislation in the 540s refers explicitly to depopulation and to the difficulty of collecting taxes, and imposes collective liability on surviving landholders for the assessments of abandoned holdings — the epibole. That is administrative evidence, not rhetoric.

Building and campaigning slowed. The great construction programme of the 530s, described in the reign of Justinian, thins out markedly after 542, and the Italian war dragged on for another twelve years with chronically inadequate forces.

Medical practice was tested and found wanting. Byzantine physicians worked within a Galenic framework in which epidemic disease was caused by corrupted air, and their responses — flight, fumigation, dietary regimen — followed from it. The hospitals of Constantinople, described in Byzantine medicine, were overwhelmed. Aëtius of Amida and later Paul of Aegina describe bubonic swellings in clinical terms without connecting them to rodents or fleas, a connection not made anywhere until the 1890s.

The religious interpretation dominated. Plague was understood as divine chastisement, and the responses were liturgical: processions, litanies, the institution of supplicatory services. Several feasts and hymns in the Byzantine calendar trace their origin to plague years, and the practice of the intercessory procession with the icon of the Virgin through the streets of Constantinople belongs to this period.

The End of the First Pandemic

The last recorded outbreak of the cycle struck Constantinople in 747–748 and was severe enough that Constantine V had to repopulate the city with settlers from Greece and the islands. After that the disease vanished from the Mediterranean for nearly six hundred years, until it returned in 1347.

Why it stopped is unknown. Suggested explanations include the collapse of the long-distance grain trade that had carried it, a change in rodent populations, climate shift, and the extinction of the particular lineage of Y. pestis involved — the sequenced sixth-century strains do belong to a branch with no modern descendants, which is at least consistent with the last of these.

Reading the Pandemic Today

The plague of Justinian is a case study in the limits of pre-modern demography. We have an identified pathogen, vivid eyewitness prose, a firm chronology of recurrence, and no reliable idea of how many people died. Estimates in print range from under five per cent of the affected populations to more than half. Anyone quoting a single figure — the “twenty-five million dead” that circulates widely — is repeating an eighteenth-century guess dressed in modern clothes.

What the DNA Showed

The genetic work is recent enough that most general accounts predate it, and it changed the terms of the debate.

In 2005 a German team recovered Yersinia pestis DNA from sixth-century burials at Aschheim in Bavaria. The result was initially contested; independent confirmation followed, and by 2014 a full genome had been sequenced from the same site. Further recoveries have come from sites in Spain, France, England and elsewhere.

Three findings matter.

The pathogen is confirmed. A century of argument about whether the sixth-century pandemic was plague, smallpox, typhus or something unknown is over. It was plague.

The strain is a dead branch. The sixth-century lineage sits on a branch of the Y. pestis family tree with no known modern descendants. It is not ancestral to the Black Death strain, which emerged separately from a Central Asian reservoir some seven centuries later. The two pandemics were independent emergences.

The geographical spread is real. Burials as far apart as Bavaria, Spain and England carry it, which confirms that the written reports of a pandemic reaching the north-western edge of Europe were describing the same disease and not a local epidemic.

What the genetics cannot supply is mortality. DNA from a dozen sites establishes presence, not proportion, and the demographic question remains exactly where it was.

The Climate Context

The plague arrived in the middle of a documented climatic disturbance, and the coincidence has attracted a great deal of recent work.

Ice cores and tree rings record a severe cooling beginning in 536, associated with one or more large volcanic eruptions — the “Late Antique Little Ice Age,” with the coldest decades of the last two millennia falling between about 536 and 550. Procopius, Cassiodorus and John of Ephesus all describe a year in which the sun gave no proper light and crops failed.

Whether the cooling contributed to the pandemic is unresolved. Proposed mechanisms include harvest failure and famine weakening populations, and climatic stress driving rodent movements. Sceptics note that the correlation is suggestive and the causal chain unproven, and that the eruption-plague-collapse narrative has been assembled rather enthusiastically in some popular accounts.

What is not in doubt is that the 530s and 540s were an unusually bad two decades in the eastern Mediterranean by every independent measure available: climate proxies, written reports of famine, and the pandemic.

Where to Read Further

Procopius’s plague chapter (Persian War II.22–23) is short, available in translation, and worth reading directly — it is the founding text of European plague literature and the model for every later account down to Defoe. John of Ephesus survives in the Syriac chronicle tradition and is the other eyewitness. For the modern argument, the maximalist and sceptical positions have both been set out at length in the last decade, and a reader who looks at one should look at the other.

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