The Mongols were a rowdy a bunch to say the least. Genghis Khan, the O.G. Mongol leader, reportedly killed over 40 million people while he was in power. In the process, he united the warring Mongol tribes and conquered most of Asia. After his death in 1227, more Mongol leaders emerged to maintain the large empire, and they were equally crazy. The most insane one of all was Jani Beg, the empire’s western commander, who, after running out of artillery, decided to use dead, plague infested bodies as cannon balls during the Siege of Caffa.

The crazy story starts back in November 1346 when Beg was trying to capture the city of Caffa in modern-day Crimea. Though his forces were much stronger and larger, an unknown enemy laid waste to Beg’s men midway through the battle: the plague. It is believed that the plague, or Black Death, made use of Genghis Khan’s trade routes by hitching a ride on the back of rats who were infested by fleas. Once bitten, a person slowly deteriorated, developed nasty boils and died.

After the disease ravished Beg’s army, he decided to take advantage of the situation by hurling the dead soldiers like cannon balls over the walls of the city. Militarily speaking, this tactic had a few advantages: it got rid of the dead, scared the hell out of the citizens of Caffa, and spread the plague inside the fortress like a biochemical weapon. Morally speaking, it was one of the grossest acts of war ever committed.

After a year of fighting, Beg had to eventually settle for a negotiation in 1347 after the plague killed too many of his troops. This historic event had much further reaching repercussions than anyone expected, though. Since no one wants to live in a city where dead bodies are littering the streets, many of Caffa’s citizens fled to Europe when the plague hit, which, in turn, spread the disease to the continent. From there, the plague rampaged through most of the world resulting in the death of around 50 million people.

Jani Beg goes down in history as not only the first military commander to use biological weaponry but also the man responsible for spreading the plague around the world.