Did the Mongols Really Intentionally Spread the Black Death?

A popular story claims that, during the siege of the city of Caffa in Crimea in 1346, the Mongol besiegers catapulted the bodies of plague victims into the walled city, thus causing an outbreak of plague in the city. Supposedly, Genoese traders who were in the city tried to flee in ships and thereby inadvertently introduced the plague to Sicily. Thus, according to the story, the Mongols are ultimately responsible for the introduction of the plague to western Europe.

How much truth is there to this story, though? Is it just made up? Did the Mongols really try to spread the plague intentionally? If so, are they really responsible for the introduction of the Black Death to western Europe? Let’s investigate the sources to find out.

The tale of the Mongols and the plague

The whole story about the Mongols supposedly deliberately spreading the plague comes from a single medieval source: the Historia de Morbo, written by Gabriele de’ Mussis (lived c. 1280 – c. 1356), a lawyer who lived in the city of Piacenza in northern Italy. Here is his account, as translated by Rosemary Horrox:

“Oh God! See how the heathen Tartar races, pouring together from all sides, suddenly invested the city of Caffa and besieged and trapped the Christians there for three years. There, hemmed in by an immense army, they could hardly draw breath, although food could be shipped in, which offered them some hope. But behold, the whole army was affected by a disease which overran the Tartars and killed thousands upon thousands every day. It was as though arrows were raining down from heaven to strike and crush the Tartars’ arrogance. All medical advice and attention was useless; the Tartars died as soon as the signs of the disease appeared on their bodies: swellings in the armpit or groin caused by coagulating humours, followed by a putrid fever.”

“The dying Tartars, stunned and stupefied by the immensity of the disaster brought about by the disease, and realising that they had no hope of escape, lost interest in the siege. But 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, although they dumped as many of the bodies as they could in the sea. And soon the rotting corpses tainted the air and poisoned the water supply, and the stench was so overwhelming that hardly one in several thousand was in a position to flee the remains of the Tartar army. Moreover one infected man could carry the poison to others, and infect people and places with the disease by look alone. No one knew, or could discover, a means of defense.”

This all sounds very dramatic, but it becomes a lot less compelling once you learn that Gabriele never actually saw any of the events he describes. He was at home in Piacenza the whole time. We don’t know if he interviewed eyewitnesses of these events, but its seems unlikely, given that he was writing several years later when the Black Death was at its height.

Most likely, this horrifying and detailed account is based on some combination of rumor and speculation. Therefore, it is entirely possible that there may not be any truth to the part about the Mongols catapulting dead bodies at all. It may just be a tale someone came up with.

ABOVE: Illustration from Rashid ad-Din’s Jami al-Tawarikh of an early fourteenth-century Mongol siege—although not the Siege of Caffa

How the plague spreads

Even if it is true that the Mongols hurled corpses of plague victims over the walls of the city using catapults, it is relatively unlikely that this is really how the plague entered the city. As I discuss in this article I wrote in March 2020 about plague doctors, the plague is caused by the gram-negative, sporeless, non-motile, coccobacillus bacterium Yersinia pestis. This bacterium can cause three different kinds of infections:

• Bubonic plague, the most common and least deadly form of the plague, which is primarily transmitted through bites from fleas carrying the disease
• Pneumonic plague, a deadlier and rarer form of the plague that occurs when Yersinia pestis infects the lungs. This form can develop as complication of bubonic or septicemic plague or be independently transmitted through the breathing in of airborne droplets carrying the Yersinia pestis bacterium.
• Septicemic plague, the rarest and deadliest form of the plague, which cannot be transmitted from person-to-person, but develops as a complication of bubonic or pneumonic plague when Yersinia pestis bacteria multiply in the blood

There are only three ways the plague can be transmitted:

• Being bitten by a flea or other insect that has become infected after biting a rodent or other animal infected with the disease
• Direct, skin-to-skin contact with the lymph node tissue or bodily fluids of an infected person
• Breathing in airborne droplets carrying the Yersinia pestis bacterium straight from the lungs of an infected person

Dead bodies can’t breathe, talk, or cough, which means the only ways you can catch the plague from a corpse is if you come into direct physical contact with the lymph nodes or bodily fluids from that corpse within a relatively short period after the person’s death, or the corpse is infested with infected fleas and one of those fleas bites you.

It is therefore plausible that catapulting bodies of plague victims into a walled city could introduce the plague to that city—but it is far more likely that the plague was already introduced to the city by infected rodents, which are the primary means by which the disease is spread.

Even if we assume that the Mongols are responsible for the introduction of the plague to the city of Caffa, it is virtually certain that the plague reached western Europe by several different routes at around the same time and that it was not solely introduced to western Europe by people fleeing from Caffa.

ABOVE: Photograph from Wikimedia Commons of a wild brown rat

The Mongol story and current politics

There are no other surviving sources to corroborate Gabriele de’ Mussis’s account of the Mongols deliberately spreading the plague by catapulting the bodies of plague victims into the city of Caffa. His account is second-hand at best, but it does date relatively close to the time of the events he describes. A year ago, I probably wouldn’t have questioned it, but current events have led me to grow more skeptical.

In late April 2020, President Donald Trump promoted a conspiracy theory that COVID-19 might have been secretly genetically engineered by scientists in a Chinese government laboratory. He even implied that the virus might have been released deliberately by the Chinese government, presumably in order to cripple the economies of nations around the world.

There is no evidence to support any part of this conspiracy theory. Furthermore, it doesn’t really make sense why the Chinese government would release a virus knowing that it would kill a large number of Chinese citizens and cause great panic and instability within China itself.

Despite this, President Trump has continued to promote claims that COVID-19 was created by or is being spread by the Chinese government. For instance, in a tweet on 20 July 2020, he called COVID-19 “the Invisible China Virus” and, in a tweet on 21 July, he called it “the China Virus.”

Hearing these insane conspiracy theories makes me wonder if Gabriele de’ Mussis’s story might simply be the fourteenth-century equivalent. When terrible pandemics and other natural disasters occur, people often feel the need to blame someone. It’s hard for people to accept that a devastating disease could spread rapidly across the globe all on its own. People assume that there must have been Mongol warriors with catapults or Chinese researchers experimenting with viruses. In reality, most of the time, it’s just nature doing its best to kill everyone.

ABOVE: Image of a tweet in which Trump calls COVID-19 “the Invisible China Virus”