You don’t need to be the biggest ancient history buff to know that the Roman army was among the greatest military forces the world has even seen. When it came to conquering territory, they were remarkably efficient. The empire swelled to more than five million square kilometers in size, before ultimately collapsing because its sheer size made it utterly impractical to defend and administer.

Along the way, the Romans conquered Greece, Gaul, and so many other regions in between. Needless to say, they fought numerous bloody wars to claim and maintain control over such lands. As successful as they tended to be, they suffered some devastating losses too: the Battle of Teutoburg Forest, of approximately 9 CE, saw three Roman legions destroyed in an infamous, cunning ambush attack at Kalkriese in modern day Germany. This fearsome fighting force of the ancient world matched wits against some of the finest generals of the period, including Carthage’s Hannibal, and it certainly didn’t always come out on top.

The word “Mithridatism,” per Merriam-Webster, is defined as “tolerance to a poison acquired by taking gradually increased doses of it.” This curious word is derived from the name of one of Rome’s other foes, Mithridates, who did just that. As it turned out, the method worked well. According to the famous story, it worked far too well when it came to his downfall.

Who Was Mithridates?

The Romans seemed to have a way of driving their foes to desperate measures, so desperate and legendary that they become embedded in our language forever. The phrase “Pyrrhic victory,” meaning a win achieved at such high costs that it may as well have been a loss, is a reference to the story of king Pyrrhus. The ruler of Epirus in Greece launched an assault on the Italian region and won two victories against the Romans, in 280 and 279 BC. Neither were decisive and both were very costly, and he was forced to flee with his remaining troops a few short years later.

Mithridates VI Eupator, or Mithradates the Great, was another king (this time of Pontus) who brought the fight to the Romans and enjoyed some success in the process. As with many rulers during this turbulent time, he attempted to balance maintaining and expanding his territory with the need to appease and cooperate with other rulers in the region (Nicomedes III of Bithynia being one of the major players), and, inevitably, squabbles and all-out warfare often ensued.

King of Pontus Mithridates VI.

King of Pontus Mithridates VI. Via Wikimedia Commons (CC BY-SA 2.5).

Nicomedes staged an invasion of Mithridates’ territory, and the Romans took the former side. Mithradates seemed to have repulsed them in impressive fashion, but this was only the beginning of a long conflict that would have far-reaching consequences. By 85 BCE, Mithridates was forced to seek peace, losing the territory he had gained during his campaign. This wouldn’t be the last the Romans would see of this persistent foe, though, nor the last defeat he would suffer.

Britannica goes on to state that an invasion by Lucius Licinius Murena marked the beginning of a turbulent decade or so between the two powers. The war that began between them afterwards was marked by shifting fortunes on both sides, but this second loss would be Mithridates’ ultimate undoing. A capable general, he was no stranger to warfare, but it seems that a life spent in its shadow took its toll on him. Though he bested the Romans on several occasions, he took great measures to try and protect himself from them, and from any other foes he encountered. Mithridates has come to be known as the poison king, and his experimentations with such substances make it abundantly clear why.

A Passion For Poisons

The Vintage News reports that Mithridates had good reason to fear poisoning: his father, Mithridates V, had been killed in 120 BC. The sneaky method used? Poison, of course, which the killer managed to sneak into his food. Becoming ruler came with tremendous responsibility, privilege and danger in equal measure, as the position brought about enemies who sought to kill their powerful foes. To survive as king during these turbulent times, it seemed, the poison king (not his father, who was sadly the poisoned king) had a brainwave: if he regularly consumed low doses of poison, his body would develop a tolerance for it. If he was then maliciously poisoned, he would not be killed.

Illustration of Mithridates VI

Illustration of Mithridates VI. Via Wikimedia Commons.

According to War History Online, the king conducted extensive experiments with poisons. He reportedly found a ready source of subjects for his research: criminals who had been condemned to be executed. In this way, his knowledge of poisons and antidotes alike blossomed. Perhaps, then, he knew just how much to administer to himself to build up a tolerance and ultimately survive the threat of poisoning. An intriguing concept, and there’s certainly some science behind it.

The study “Human Adaptation to Arsenic-Rich Environments,” from Carina M. Schlebusch et al (via Oxford Academic), demonstrates how such a thing could be possible.

“We found that inhabitants of the northern Argentinean Andes, an arid region where elevated arsenic concentrations in available drinking water is common, have unique arsenic metabolism,” the Abstract of the study states. The results suggest that those who live in the region and so frequently partook in such water were more resistant to the effects of arsenic. “The people living in this area have a relatively high arsenic exposure and an efficient and less toxic metabolism,” Dr Karin Broberg stated to The Daily Mail. While this did not render the people of San Antonio de los Cobres immune to the deadly effects of arsenic, it did mean that they were tolerant to it to a certain degree. Through the gene AS3MT, they have, the outlet reports, developed a metabolism that can cope with it rather more effectively.

Elemental arsenic — mineral specimen.

Elemental arsenic — mineral specimen. Credit: Tomihahndorf Via Wikimedia Commons (CC BY-SA 3.0).

It’s quite possible, then, that Mithridates’ ministrations worked in the same way. Careful exposure to smaller degrees of poison could, over time, have afforded him more tolerance to it. The hope was that his enemies would be unable to poison him. According to legend, when he reportedly poisoned himself, it didn’t work either!

As Stanford University’s Adrienne Mayor explained to The Naked Scientists in 2020, “there were myriad poisons known in antiquity from toxic plants to snake venoms … there were also many minerals in his kingdom that were highly toxic, such as arsenic.” It seems that, just as with the San Antonio de los Cobres villagers, Mithridates did develop a resistance to arsenic (which was well-known and deviously ‘popular’ then). The major difference is, he exposed himself to smaller doses of it intentionally! According to Mayor, he developed a universal antidote of sorts known as Mithridatium, the details of which are long lost.

It Seems He Didn’t Really Try To Poison Himself

After his downfall, Pharnaces II, his own son, assumed his throne. Mithridates, reportedly, feared that he would be delivered to his long-time foes, the Romans. To prevent such a fate, he is said to have attempted to poison himself. Naturally, though, his attempt failed. Instead, the story goes, a trusted ally named Bituitus killed him on his own orders. Death by the sword, rather than poison!

Lapham’s Quarterly goes on to explain that it was the famous Galen who shared this story, and seemingly popularized it. It’s well known to this day. Galen did not present the tale as fact, the outlet goes on, and it certainly seems a little fanciful: “The most obvious concern is that the king, who was an expert on antidotes, would have been unlikely to take a poison that he had every reason to believe would not work.”

Perhaps it was merely an attempt to give this accomplished and powerful ruler’s story a conclusion worthy of his memory. It’s certainly memorable, and reflective of Mithridates’ renown as an expert in poisons. He may not have literally died in this ironic fashion, but he has been known for centuries as having done just that.

By Chris Littlechild, contributor for


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