The Mongol Catapult That Threw Plague Corpses Into the Genoese Garrison Probably Did Not Actually Happen

The most-quoted single passage in the historiography of the Black Death comes from the Historia de Morbo sive Mortalitate of the notary Gabriele de’ Mussis of Piacenza, composed in 1347 or 1348:

The Tartars, dying as soon as the signs of disease appeared on their bodies — swellings in the armpit or groin, caused by coagulating humors, followed by a putrid fever — soon despaired of recovery. They ordered corpses to be placed in catapults and lobbed into the city in the hope that the intolerable stench would kill everyone inside. What seemed like mountains of dead were thrown into the city, and the Christians could not hide or flee or escape from them.

The passage is the source of the famous story that the Black Death arrived in Europe through a literal act of biological warfare — a Mongol khan turning plague corpses into siege weapons against a Christian Italian garrison. The story has been reprinted in essentially every modern history of the plague, treated as one of the founding events of biological warfare, and used as the canonical opening anecdote for textbooks on epidemic disease.

It probably did not happen as written.

Why de’ Mussis is a problem

De’ Mussis was not at Caffa. He was a notary in Piacenza in northern Italy, approximately 2,000 km west of the Crimean siege. He never travelled east of Lombardy in his documented life. His Historia was composed approximately 18 months after the siege had ended, on the basis of reports brought back by Genoese refugees fleeing through Italian ports.

He was also writing in a specific literary tradition. The Historia is not a sober chronicle: it is a substantially apocalyptic theological-rhetorical composition that frames the Black Death as divine judgement on Christian sin, with the Mongol siege functioning as the dramatic prologue. The corpse-catapult image works rhetorically in that frame — pagan barbarians using the bodies of their own dead as missiles to defile a Christian city — in a way that suggests literary construction rather than direct testimony.

Modern critical reading of the Historia notes that no other contemporary source confirms the catapult story. The Mongol chronicles do not mention it. The Genoese commercial archives — which substantially survive for the period — record the evacuation of Caffa but contain no reference to corpse-bombardment. The Persian historian Hafiz-i Abru, writing within decades of the events from sources closer to the Golden Horde, gives a different account of the siege’s end.

What probably did happen

The substantive reconstruction modern historians offer is something like this. The Mongol army besieging Caffa in 1346 did experience a major outbreak of plague — broadly consistent with what we now know about the contemporaneous spread of the disease westward from its endemic reservoirs in Central Asia. The disease killed enough of Jani Beg’s army to make the siege militarily unsustainable; the khan lifted the siege and withdrew. The Genoese garrison emerged from the city, found the abandoned Mongol camp littered with plague corpses, and contracted the infection through ordinary epidemiological contact rather than through any deliberate catapult act.

The plague then travelled west on the Genoese ships fleeing Caffa for Italian ports, exactly as de’ Mussis reports. By October 1347 the disease was at Messina; by January 1348 it was at Genoa, Marseille, and Venice; by April 1348 it was at Florence and was killing the people whose bodies Boccaccio’s neighbours were dumping into the Santa Maria Novella pits.

The substantive arrival of the Black Death in Europe via Caffa is documented. The literal corpse-catapult is probably literary embroidery.

The story has nonetheless been too good to discard. It survives in most modern accounts of the plague’s arrival because it provides the dramatic narrative anchor the otherwise diffuse epidemiological reconstruction lacks. The standing scholarly position is roughly: the catapult image is probably symbolic rather than factual, but the underlying causal connection (Mongol siege → plague exposure of besiegers → contamination of Genoese garrison → ships sailing west) is sound.