How the Black Plague arrived in Europe — The birth of biological warfare

The use of germs and pathogens in war is one of the dirtiest tricks humans can use against their own kind. We’re used to thinking to it as a weapon born during the first World War, but in reality, biological warfare finds its origins way earlier in history.

The first documented use of a biological weapon coincides with a precise event that might have played a role in one of the greatest disasters in history: the black plague pandemic that starting from 1347 hit Italy and then spread over all Europe. In less than 5 years over 20 million people died, almost one-third of the whole European population of the time.

The plague is an infectious disease caused by the bacterium Yersinia pestis which causes the inflammation of the lymph nodes, swelling them grotesquely and filling them with pus, hence the name “bubonic plague” (from the Greek word βουβών which means “groin”, or “bulge”). The incubation period is very short, from two days to a week, and death is usually as quick as painful. At the time there was no medical knowledge of the disease so the only explanation for it was simply that it was the end of the world, the Apocalypse.

These are the words of a scholar of the time: “The bells stopped making any sound and the crying stopped. The only thing left to do was waiting for death, someone fell to madness staring blankly, others saying the rosary, someone else indulging to the worst vices. Many said that that was the end of the world!”.

The disease is transmitted through the bite of infected fleas that usually infest central Asian rodents, mainly in the region of the Altaj, nested between Kazakhstan and Mongolia. Thanks to recent dendrochronological studies, which is the study of tree rings, changes in the climatic conditions have been found that led to a growth of the rodents’population and therefore of the fleas that parasitized them. When the temperature dropped again the number of rodents decreased. That meant that each gerbil, groundhog, and squirrel had more fleas on it. When these animals met other animals, such as the camels used in the caravans on the silk road, the fleas could more easily infect them.

Thanks to a research of the University of Oslo and Berna it has been found that to each significant climate variation in Asia coincides with an outbreak of plague in Europe, with a delay of 12–15 years, which is the time needed for the infection to reach the West. This new discovery dismissed the old hypothesis that claimed that the infection first arrived in 1347 and then the European forests, and the animal within, became a source for the disease to cyclically resurface.

Let’s move to Caffa, now called Feodosia in Crimea, at the time an important and florid commercial port on the southern coasts of the Black Sea. The city was in the hands of the powerful Republic of Genoa, one of the great Maritime republics that controlled the shipping routes to and from the East. According to the French historian Michel Balard, in 1343, in a brawl, a Tartar got killed by genoeses gendarmes. This murder was the casus belli that allowed Janibek Kahn to siege the city hoping to gain control of it. The siege was unsuccessful and the Khan was forced to retreat only to return two years later with a larger army. What he didn’t know was that among his ranks there was an enemy way more dreaded than the genoeses, ready to kill everyone, friend or foe.

The plague spread among the besiegers, decimating them. The khan lost again, but this time his retreat wouldn’t be victimless: determined to destroy the city and kill his inhabitants he ordered to catapult the corpse of the plague victims. The infection hit hard the genoeses and soon the survivors left the city to return to Italy. They landed in Messina, in Sicily. It was 1347 and from there the disease spread like wildfire to the rest of the peninsula and then to the rest of Europe.

The rest is history. The Black Plague changed an entire continent, culturally, socially, genetically, economically and politically. After those years the world was not the same, and it all started with some changes in the climate of a land on the other side of the Earth.