An artificial intelligence model successfully deciphered a 217-year-old encrypted military letter issued under Napoleon Bonaparte’s orders, unmasking operational troop movements from 1809 in just six hours.
A hidden military dispatch sent during the Napoleonic Wars has finally yielded its secrets after more than two centuries, thanks to advanced artificial intelligence.
The breakthrough was engineered by Carter Church, an artificial intelligence researcher at cybersecurity firm SentinelOne. Working from a single, low-resolution scan published in a French army magazine in 1969, Church used the AI to process the handwritten document from start to finish, as reported by Euronews.
Origins of the 1809 Cipher from Eugène de Beauharnais to Auguste de Marmont
The letter itself was not penned by Napoleon, but rather transmitted at his direction by his stepson and the viceroy of Italy, Eugène de Beauharnais. The intended recipient was French Marshal Auguste de Marmont, who was stationed far from the main imperial forces on the eastern coast of the Adriatic Sea in Dalmatia, as detailed by G4media.
In March 1809, Europe stood on the brink of conflict as the Austrian Empire prepared to launch an offensive against France, with a significant portion of French forces still tied down in Spain. With Austrian territory sitting squarely between Marmont’s forces and the rest of the French army, the marshal ran a severe risk of isolation.
How GPT-6 Astra Cracked the Homophonic Substitution Cipher
Deciphering the manuscript presented a formidable challenge. The document contained approximately 1,300 characters—or 1,202 by 1,836 dimensions according to specific platform measurements—represented by 155 to 175 distinct handwritten symbols arranged in a homophonic substitution cipher, meaning a single letter could be represented by multiple symbols to foil linguistic pattern-matching.
Church fed the digital scan and a single directive into GPT-6 Astra. The AI sliced the document into rows, transcribed the handwritten markings, and identified which duplicate symbols corresponded to identical letters. During the process, the model located a reference table compiled by historical cryptology researcher Daniel Tant that explained 33 symbols from an older coding system.
What the Decoded Dispatch Reveals About the War of the Fifth Coalition
While historians were already familiar with much of the strategic context through surviving correspondence between Napoleon and Eugène—noted by King’s College London European history specialist Michael Rowe—the newly readable text provides a precise window into French operational planning in late March 1809, roughly two weeks prior to the Austrian invasion.
The translated text outlines the positions and strengths of Bavarian, Polish, and French forces, noting that Russian troops were marching against Austria and that the army in Friuli numbered 80,000 soldiers.
When you receive the marching order, you must not let yourself be intimidated by a few troops or a rabble of scum.
Napoleon Bonaparte, via historical dispatch
Backed by these orders, Marmont’s forces eventually broke through the Croatian encirclement to support Napoleon, contributing to the decisive French victory at the Battle of Wagram and earning Marmont a promotion to marshal, as highlighted by Vietnam.
Verification by Cryptographers and the Future of AI in Historical Research
To ensure transparency, Church published his complete research workflow, including transcriptions, cipher tables, and scripts.
Scholars suggest that applying multimodal artificial intelligence to archival manuscripts could serve as a modern Rosetta Stone for unlocking centuries of unread historical documents that have languished due to a lack of specialized cryptographic resources.