Fair-Weather Friends: A Weird Explanation for 20% of Roman Emperor Assassinations

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Via ancient-origins.net by Alicia McDermott

Long bouts of bad weather have been blamed as a cause for the downfall of ancient civilizations around the world. Now, researchers have proposed a hypothesis that seems to support the idea that the Roman military were “fair-weather friends” to their emperors. And when the climate disagreed with them for a little too long, it seems Roman soldiers lost their loyalty to their leader. But were climate issues really enough to set off Roman emperor assassinations?

It may be simply an example of correlation, not necessarily causation, but researchers have found a lack of rain went hand in hand with 20% of the assassinations of 82 Roman emperors. The study was published in the journal Economic Letters and it provides a concise explanation for the hypothesis:

“A dictator relies on his military’s support; shocks to this support can threaten his rule. Motivated by this, we find that lower rainfall, along the north-eastern Roman Empire, predicts more assassinations of Roman emperors. Our proposed mechanism is as follows: lower precipitation increases the probability that Roman troops, who relied on local food supplies, starve. This pushes soldiers to mutiny, hence weakening the emperor’s support, and increasing the probability he is assassinated.”

So, even if the Emperor was not killed directly by the military, his security would have been decreased as the soldiers lost their faith in his ability to provide them with sufficient food. Live Science reports that lead researcher Cornelius Christian, an assistant professor of economics at Brock University in Ontario, Canada, made the correlation between the weather and the assassination of Roman emperors by examining climate data from a 2011 study and combining that with documentation of military mutinies and Roman emperor assassinations.


It all came together in statistics. As Christian told Live Science, “it was really just a question of piecing together these different pieces of information. Lower rainfall means that there's more probability of assassinations that are going to take place, because lower rainfall means there's less food.”

He gives the example of Emperor Vitellius who was murdered in 69 AD. “Vitellius was an acclaimed emperor by his troops. Unfortunately, low rainfall hit that year, and he was completely flabbergasted. His troops revolted, and eventually he was assassinated in Rome.

Although he sees a strong correlation for the two, Christian also recognizes that a drought probably wasn’t the sole cause for an emperor to be killed, “We're not trying to claim that rainfall is the only explanation for all these things. It's just one of many potential forcing variables that can cause this to happen,” Christian said .

One of the emperors who almost certainly wasn’t killed due to bad weather, but more likely due to his bad temperament and actions, was Emperor Commodus, killed in 192 AD. While the military was involved in Commodus’ assassination, history tells us they took the drastic action because the emperor saw himself as above the law and forced gladiators to let him win in the Colosseum.

This is certainly not the first time long-lasting bad weather has been linked to social unrest. It has been proposed , for example, that inhabitants in the Old Kingdom of Egypt were rebellious following periods of drought and bad taxes. And a study published in Plos One in 2013, showed that climate change occurring towards the end of the 13th century BC may have even caused the collapse of the Eastern Mediterranean civilizations.

As Archaeology points out, there are critics to the Roman Emperor-drought hypothesis. The main issue they tend to have with it is its simplicity. While the droughts and subsequent food shortages sound plausible aspects to incite dissidence against the emperors, disease, war, and economic concerns such as inflation could have easily played a role in their assassinations as well.

Jonathan Conant, who wasn't involved with the study but is an associate professor of history at Brown University, told Live Science, “For me, [the rainfall-assassination hypothesis] adds another layer of complexity and nuance to our understanding of the political history of the Roman Empire, especially in the third century.”

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