The Black Death

“O happy posterity, who will not experience such abysmal woe—and who will look upon our testimony as a fable.”
— Francesco Petrarca, Familiar Letters (1349)

It began, as plagues do, far from the people who would write it down. High in the grasslands of Central Asia, in the burrows of marmots and gerbils along the old caravan roads, lived a bacterium called Yersinia pestis. It had smoldered there for a very long time, until the Mongol peace braided Eurasia into a single highway of silk, silver, and grain—and gave an infected flea a ride across the world. In a small Christian cemetery at Kara-Djigach, near Lake Issyk-Kul in modern Kyrgyzstan, a cluster of headstones dated 1338 and 1339 carries a single grim cause of death in Syriac: pestilence. Geneticists have drawn from the teeth beneath those stones the closest known ancestor of every Black Death strain yet sequenced.¹ What follows is the road it took, told from the walls and windows of the people who watched it come.

Caffa, Autumn 1346

Jani Beg, Khan of the Golden Horde, has been besieging this city long enough to hate every stone of it. Caffa is a Genoese trading colony on the Crimean coast—fat, walled, insolent, and fed from the sea, so that no landward army can properly starve it. The khan of the greatest of the Mongol successor states, lord of the steppe from the Danube to the Ural, has been reduced to sitting in the mud outside a merchants’ town, waiting.

Then his army begins to die. Not of arrows, not of hunger—of swellings. Men wake with black lumps in the groin and armpit and are corpses by the third day. The tumens melt faster than any sortie could thin them; the camp fills with a smell the oldest campaigners do not recognize. The steppe has always known this sickness in its marmots and its fleas, but no one in the khan’s tent knows that, and it would not help if they did.

What Jani Beg does next is recorded by a notary from Piacenza named Gabriele de’ Mussi: the khan has the corpses of his own plague-dead loaded onto the siege engines and hurled over the walls into the city, so that the intolerable stench might kill everyone inside. The Genoese throw the bodies into the sea as fast as they land, but the wells foul, and the sickness is already among them.²

The siege dissolves. And the defenders, with the plague at their backs, do the most human thing imaginable: they run. The galleys are loaded, the prows point home toward Italy, and Caffa’s merchants sail west carrying their cargo, their rats, and their death. The khan has lost the siege. In a sense no one aboard those ships yet understands, he has also won it more completely than any siege in history.

Constantinople, Summer 1347

John VI Kantakouzenos, Basileus of the Romans, has waited five years for this throne, and he has held it for barely five months when the galleys from the Black Sea bring his reward. The empire he seized in February—after a civil war against a child emperor’s regents that wrecked what little of it remained—is the front door of Europe, the toll-gate between the Black Sea grain trade and the Mediterranean. Everything passes through the Queen of Cities. Now this passes through too.

The pestilence takes the harbors first, then the streets, then the palace. It takes Andronikos, the emperor’s youngest son. There is nothing a basileus can command against it; the emperor who out-schemed every rival in Romanía sits helpless as any dockworker while the boy dies.

So he does the one thing left to an educated Roman: he writes. In his memoirs, Kantakouzenos sets down the plague of his own city in sentences deliberately shaped after Thucydides’ plague of Athens, eighteen centuries before—the same progression of symptoms, the same despair of physicians, the same dissolution of custom—as if reaching across time for the only company adequate to the catastrophe.³ The empire had survived Persians, Arabs, Crusaders, and its own civil wars. Its historian-emperor understood, perhaps before anyone else in Europe, that this enemy belonged to a different category, and that the only weapon that had ever worked against it was literature.

From the Golden Horn, the galleys carry it onward: to Trebizond, to Alexandria, to the West.

Messina, October 1347

Michele da Piazza, friar of the Order of Saint Francis, will spend years writing down what the dockworkers of Sicily found in the harbor that month, and his account never loses its tone of a man describing something he still cannot believe.

Twelve Genoese galleys limp into Messina. The harbor-men who go aboard find sailors slumped at the oars with, as the friar writes, sickness clinging to their very bones—most of the crews already dead, the remainder dying, black swellings at groin and armpit, some coughing blood. These are the ships of Caffa and the Romania trade, the ordinary autumn traffic of the sea, arrived on schedule and crewed by corpses.

The Messinese understand enough to be terrified. They drive the ships back out to sea at spear-point—the first quarantine in the story, improvised a generation too early and three days too late. The plague is already ashore in the port district. Within weeks Messina is dying so fast that its citizens flee to the fields and carry the sickness inland with them; the ships, expelled, simply make land elsewhere. From Sicily the pestilence leaps to Genoa and Marseille, and into the soft underbelly of Europe.

The friar records one more detail the age found significant: when the Messinese begged the archbishop of neighboring Catania for the relics of Saint Agatha, the Catanians refused to let them travel—the first of many cities to discover that in this year, charity and self-preservation had become opposites.

Avignon, Spring 1348

Guy de Chauliac, physician to the Pope, is the most learned surgeon in Christendom, and he begins this season by writing down a sentence no physician enjoys: the disease was shameful to the doctors, who could achieve nothing.

Avignon in 1348 is the capital of the Church—for four decades now the popes have sat here on the Rhône rather than in Rome, in that seventy-year Babylonian captivity known as the Avignon Papacy—seat of Pope Clement VI, a city of cardinals, bankers, petitioners—and now of carts. The mortality outruns the graveyards so completely that Clement consecrates the river Rhône, so that corpses thrown into its waters count as buried in holy ground. The Pope himself retreats to his chamber and sits, on his physician’s advice, between two great fires, which may in fact have worked—not against corrupted air, as de Chauliac reasoned, but against the fleas neither of them knew to blame.

The court around them empties. In April, in this city, dies a woman named Laura, whom a poet named Petrarch had loved at a distance for twenty-one years; the plague writes the ending of the most famous love story of the century in a parish register.

De Chauliac does not flee. He stays, treats the dying, catches the plague himself, endures six weeks of it, and survives to write a clinical description so precise we still recognize it: one form with the black swellings—the buboes—killing in five days; another, worse, with fever and the coughing of blood, killing in three, passing—he saw it clearly—from breath to breath, so that one man caught it from another merely by looking at him, or so it seemed. Without knowing it, he had separated bubonic from pneumonic plague, the second needing no flea at all.⁴

Florence, Summer 1348

Giovanni Boccaccio, citizen of Florence, is thirty-five years old and watching the richest city in Europe dissolve.

Florence is banking, wool, and crowding—a perfect instrument for the pestilence. Boccaccio will set the scene at the front of the Decameron, and what horrifies him is not the death but the unraveling: brother abandons brother, the uncle his nephew, the sister her brother, and—worse, and almost unbelievable to him—fathers and mothers refuse to visit and tend their own children, as if they had not been theirs. The sick die attended by the greed of servants or by no one. The great funerals of Florentine custom shrink to nothing; the dead are carried on planks by hired becchini, two or three households to a bier.

The consecrated ground runs out. Great trenches are dug, and the dead are laid in, he writes, as merchandise is stowed in the hold of a ship, layer upon layer, each covered with a little earth, until the trench is filled to the top.

His answer to the catastrophe is the book itself: seven young women and three young men who flee to a villa in the hills and tell each other a hundred stories while the city dies below—civilization rebuilt at table-size, out of nothing but narrative and good manners. It is either the most escapist frame in literature or the most defiant; probably it is both.

Siena, August 1348

Agnolo di Tura, called the Fat, is a shoemaker and part-time chronicler, and he writes the single most devastating sentences the plague produced anywhere in Europe.

Siena in 1348 is at the height of its ambition—rich enough to be rebuilding its cathedral into the Duomo Nuovo, intended to be the largest church in Christendom. Then the mortality arrives, and Agnolo records it in the flat voice of a man past weeping. If the Black Death left behind one paragraph that shows exactly what it was like to stand inside it, it is this one:

The bells do not toll because the city has ordered them silenced—the constant ringing was destroying what remained of morale—and because, increasingly, there is no one left to ring them.

Siena survives, but it never recovers its nerve. The workforce and the money die together, and the Duomo Nuovo is abandoned half-built. Its unfinished arches still stand against the Tuscan sky: the most honest war memorial the plague ever received, a monument to the exact moment a city stopped believing in its own future.

Strasbourg, February 1349

Peter Swarber, Ammeister of Strasbourg, has the strangest position in this story: he is fighting the plague’s madness before the plague itself has even arrived.

The pestilence is still far off, working up the Rhône, but the rumor travels faster than the fleas: that the wells are poisoned, and that the Jews have poisoned them. It is nonsense—where the plague has struck, Jews die exactly like everyone else, and Pope Clement has said so plainly in bulls of 1348 ordering the killings stopped. Along the Rhine it makes no difference. Town by town, the massacres march ahead of the disease, driven not by infection but by terror—and, very often, by the convenient erasure of debts owed to the murdered.⁶

Swarber and the moderates on the council refuse to hand over the city’s Jews. Confessions extracted on the rack in other towns are read out against him; the guilds and the debt-burdened patricians circle. In the second week of February the council is overthrown, Swarber is deposed and driven from the city, and his property is confiscated. On 14 February 1349—St. Valentine’s Day—Strasbourg burns several hundred of its Jews on a wooden scaffold in their own cemetery. The plague has not yet reached the city. When it arrives months later, it kills Strasbourgeois at the same rate as everyone else, the community’s debts to its murdered creditors having been, in the interval, declared void.

Through these same Rhineland towns march the Flagellants—processions of penitents who strip to the waist and whip themselves bloody in the squares, bleeding in time to their own grim hymns, convinced that human sin has earned this scourging and might be paid down in blood:

They too turn on the Jews wherever they pass. Clement VI, who has every theological sympathy for penance, condemns the movement in October 1349. By then the fire has largely burned through: along the Rhine, the plague’s cruelest work was done by the healthy.

Ragusa, July 1377

The Rector and Major Council of Ragusa (Dubrovnik) govern a small merchant republic that lives, like Caffa once did, entirely by the sea—and thirty years of recurring pestilence have taught the Adriatic’s most careful merchants an actuarial lesson: the plague is not an event but a weather system, and it always arrives by ship.

So in this month the council enters into its books a decree with none of the poetry of the chronicles and more effect than all of them: veniens de locis pestiferis non intret Ragusium—those coming from plague-ridden places shall not enter Ragusa until they have first remained in isolation, on the islet of Mrkan or at Cavtat, for thirty days. The trentino. Soon lengthened—forty being a number of good biblical standing, and safer besides—to the quarantino.

From that forty-day wait comes the word quarantine. It is the first institutional answer to the pandemic anywhere in the world: not prayer, not blame, not medicine, but administration—a rule, a register, a waiting period, enforced by a harbor master. Nobody on the council knows what Yersinia pestis is. They do not need to. They have observed the interval between a ship’s arrival and a city’s dying, and they have legislated for it. It is the one measure in this entire story that actually worked, and every public health system since is descended from a Ragusan customs regulation.

The World After

When the great wave ebbed around 1353, perhaps a third to a half of Europe was dead, and the world that crawled out from under it was permanently altered.

The sheer arithmetic of death rewrote the social order. With so many laborers gone, the survivors discovered their work was suddenly worth more, and began to demand it. Lords and kings panicked; in England the Statute of Labourers (1351) tried to freeze wages at their old levels by law, and the resentment it bred ran straight into the Peasants’ Revolt of 1381. The bottom of medieval society had learned that it could not be taken entirely for granted.

And the plague did not truly leave. It receded, and returned, and returned again for three more centuries, until the quarantino and its descendants slowly fenced it out. But the survivors of the first great mortality carried something the rest of the Middle Ages had not: the memory of a year when the bells stopped ringing because there was no one left to ring them—and the lingering, almost modern suspicion, first voiced by a grieving Petrarch, that posterity would hear all of it and simply refuse to believe a word.

Footnotes

1. Spyrou et al., “The source of the Black Death in fourteenth-century central Eurasia,” Nature (2022). The Issyk-Kul strain sits at the very root of the family tree of the lineage that exploded across Eurasia a decade later. ↩

2. Often cited as one of the earliest recorded acts of biological warfare. De’ Mussi likely never saw Caffa himself, and modern historians suspect the rats and fleas of the besieged city would have done the job regardless—but his account is the story the age told about itself. ↩

3. Kantakouzenos was not the only one to reach for Thucydides. Over the next two years, educated men everywhere found that the only language adequate to the disaster was the language of the ancient plague-writers. ↩

4. De Chauliac’s Chirurgia Magna (1363) remained a standard surgical text for centuries. His plague chapter is one of the very few contemporary accounts written by someone who treated the disease, contracted it, and lived to revise the manuscript. ↩

5. From the Cronaca Senese attribuita ad Agnolo di Tura del Grasso (in Muratori’s Rerum Italicarum Scriptores, XV.6). The 14th-century Sienese text survives in variant transcriptions; wording differs slightly between editions, and the famous English rendering is itself a light condensation. The five children, the dogs, and the end of the world are in every version. ↩

6. This is the detail that gives the lie to the whole thing: the pogroms frequently preceded the plague. They were not a response to dying. They were a response to fear. ↩

7. Loosely: Now come forth, all who would do penance / flee from the burning hell— / Lucifer is an evil companion. The same lines run through “Pain is Salvation,” the Flagellant theme on the Europa Universalis V soundtrack. ↩