AI Deciphers Napoleon's 217-Year-Old Secret Letter

An AI researcher from the Israeli-American cybersecurity firm SentinelOne, Carter Church, has deciphered a coded letter from Napoleon Bonaparte that had remained a mystery for 217 years. According to The Telegraph, Church utilized OpenAI's GPT-6 Astra model to solve the puzzle. The letter, sent in 1809 to a prominent French military leader, Auguste de Marmont, was written by Napoleon's stepson, Eugène de Beauharnais, under the emperor's orders. The text, approximately 1300 characters long, used symbols for both letters and entire words, and the key to the cipher was lost. Previously, researchers had only managed to decipher 33 symbols.

Church fed the letter and previous decryption attempts into GPT-6 Astra. The model took about six hours to transcribe the symbols and correlate them with known data. A simulated annealing method was then employed to find the most probable text by systematically testing various options, including comparisons with other preserved writings by Marmont.

The deciphered message reveals details about the movements of French and Austrian troops prior to the war between France and the Austrian Empire. "Austria attacks on all fronts simultaneously. It is rushing towards its own demise all the time," the letter from Napoleon states.

Church was motivated to attempt the decryption by a report of another AI experiment that successfully cracked the cipher of a German military letter from 1941. Researchers note that the growing capabilities of AI in pattern matching and recovering hidden information could also be used for less benign purposes, such as identifying the owners of anonymous internet accounts.