DNA Analysis Rewrites History of Napoleon’s Army Collapse

Historical Assumptions Overturned

For more than two centuries, historians and medical experts largely agreed that typhus delivered the final blow to Napoleon Bonaparte’s devastated army during its catastrophic retreat from Russia in 1812. Contemporary accounts from army doctors, the discovery of body lice on remains, and earlier DNA analysis all pointed toward this conclusion. But according to a groundbreaking study published in Current Biology, that long-standing narrative appears to be wrong.

Using advanced ancient DNA sequencing techniques, an international research team has identified entirely different pathogens as the likely primary causes of the army’s medical collapse. Their analysis of dental remains from 13 soldiers buried in a mass grave in Vilnius, Lithuania revealed traces of Salmonella enterica, which causes enteric fever, and Borrelia recurrentis, responsible for relapsing fever. Notably absent was any genetic evidence of Rickettsia prowazekii, the bacterium that causes typhus.

Technical Breakthrough Enables Discovery

What made this revisionist finding possible was a significant technological leap in how researchers handle degraded ancient genetic material. Earlier studies that had identified typhus relied on polymerase chain reaction (PCR) technology, which requires relatively intact DNA sequences to work effectively.

“Ancient DNA gets highly degraded into pieces that are too small for PCR to work,” lead author Nicolás Rascovan of the Institut Pasteur explained in the study. “Our method is able to cast a wider net and capture a greater range of DNA sources based on these very short ancient sequences.”

This technological advancement allowed the team to screen for multiple pathogens simultaneously rather than targeting specific ones, essentially letting the historical evidence speak for itself. The approach proved particularly valuable given the challenging condition of remains from soldiers who perished during Napoleon’s Russian campaign, where an estimated 400,000 of his 500,000-strong army died from combat, starvation, and disease.

Unexpected Historical Connections

Perhaps the most surprising finding emerged when researchers compared the relapsing fever pathogen strain to existing genomic databases. The B. recurrentis strain found in Napoleon’s soldiers turned out to belong to the same lineage that was present in ancient Britain some 2,000 years earlier during the Iron Age.

This discovery suggests this particular pathogen lineage persisted in Europe for millennia, yet somehow disappeared from the modern genomic record. All contemporary strains sequenced to date belong to a completely different lineage, creating something of a historical mystery about what happened to this ancient European variant.

“This shows the power of ancient DNA technology to uncover the history of infectious diseases that we wouldn’t be able to reconstruct with modern samples,” Rascovan noted, highlighting how such findings can reshape our understanding of pathogen evolution and spread across human history.

Rewriting Medical Military History

The implications extend far beyond correcting the historical record of one military campaign. According to analysts familiar with the research, this demonstrates how DNA analysis technology is transforming our ability to diagnose historical outbreaks with modern precision.

Military historians have long debated the relative contributions of battlefield casualties, starvation, extreme cold, and disease in Napoleon’s Russian disaster. While all factors clearly played roles, the new evidence suggests enteric fever—with symptoms including high fever, abdominal pain, and severe diarrhea—and relapsing fever may have been more significant than previously recognized in crippling the army’s effectiveness.

Meanwhile, the absence of typhus evidence in these particular remains doesn’t necessarily mean the disease was entirely absent from the campaign. Researchers caution that different soldier populations might have suffered from different disease burdens, and the sample size, while significant, represents only a fraction of the massive army.

What’s clear is that the marriage of advanced genomic sequencing with historical inquiry continues to yield surprising insights. As these technologies become more sophisticated, we’re likely to see more historical “certainties” overturned, giving us a clearer picture of how pathogens have shaped human events that once seemed well-understood.