October 24, 2025
3 minute read
Two amazing deadly diseases contributed to Napoleon's defeat in Russia
Pathogenic bacteria recently discovered in the teeth of Napoleonic soldiers may have caused mass infantry deaths during their retreat from Russia.
Napoleon's retreat from Moscow.
Adolph Northen; Public domain
In 1812, Napoleon Bonaparte invaded Russia with one of the largest armies in history, the Grande Armée of about half a million men. But when they were forced to retreat, harsh winter conditions, famine and disease devastated the invaders. Historians estimate that about 300,000 of these men died.
Historical evidence, early DNA research, and body lice remains found on soldiers support the idea that typhus and trench fever contributed to the army's downfall. However, the wider debate over the French retreat and the role of disease still rages on.
“This is one of the greatest mysteries in history because: Why [did] Did Napoleon lose?” says Remi Barbieri, a researcher at the Institute of Genomics at the University of Tartu in Estonia.
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Ancient DNA holds a clue. Genetic material extracted from historical fossils, skeletons And mummies dug up the secrets of our ancestors, locked in time. In a new journal study Current Biology, Barbieri and his colleagues suggest that two previously unsuspected pathogens struck Napoleon's huge army: salmonella enterica, the bacterium that causes paratyphoid fever, and Borrelia recurrent, a bacterium that is spread by body lice and causes relapsing fever. Both could prove fatal to soldiers suffering from hunger and extreme cold.
“We expected to find pathogens that had already been reported,” says geneticist Nicolas Rascovan, co-author of the study and head of microbial paleogenomics at the Pasteur Institute in France. But when researchers analyzed DNA from the teeth of 13 Napoleonic soldiers, they found no bacteria that causes typhus or trench fever, two diseases that have previously been linked to skeletons from the site. Although the team did not detect these diseases, this does not mean that they did not haunt Napoleon's army, Raskovan emphasizes.
“What [the study] shows that these people had a range of diseases,” he says.
“The research is very compelling,” says Marcela Sandoval-Velasco, an associate professor at the Center for Genomic Sciences at the National Autonomous University of Mexico, who studies molecular biology to answer questions about our past. Although the team only had 13 samples to work with, they appreciated how the researchers clearly laid out their limitations.
Skull of a soldier in Napoleon's army.
Michel Signoli, Aix-Marseille University
In 2002, researchers excavated the site of a mass grave of 2,000 to 3,000 people in Vilnius, Lithuania. Napoleonic artifacts lay scattered around the skeletons. Among them were old buttons and belts, suggesting that the remains represent soldiers of Napoleon's army who retreated from Russia in 1812. Raskovan and his colleagues chose just 13 people to preserve as many skeletons as possible. The researchers also chose this small number because they wanted the teeth in the best possible condition.
In the laboratory, the team unclenched the soldiers' teeth. They put the scraped tooth pulp into a DNA sequencing machine. After sequencing, scientists sorted the DNA results for the presence of pathogenic bacteria. They compared the suspected pathogen's DNA with known genome sequences and then matched it to two bacteria.
“Just by reading historical accounts, [it] it was impossible to suspect these two pathogens,” says Barbieri. But by developing this new methodology, researchers were able to identify bacteria from small fragments of DNA. “Personally, I’m also very excited about this methodology.”
Looking ahead, the researchers plan to continue to uncover the role of pathogens in history, albeit in different places. While Raskovan will work on infectious diseases in America, Barbieri will continue to study European history.
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