Historic military letter decoded

A military letter from Napoleon’s First Empire, which had remained undeciphered for over 200 years, was recently cracked using artificial intelligence. The letter, written in 1809, contained orders from Napoleon to one of his generals.

AI used to break the code

Engineer Carter Church used the GPT-6 Astra model from OpenAI to decipher the letter in about six hours. The only material the AI had was a blurry image of the letter from a 1969 military magazine.

Letter’s content revealed

The letter was written by Eugène de Beauharnais, Napoleon’s son-in-law and viceroy of Italy. It relayed orders from the emperor to Marshal Auguste de Marmont, who was stationed on the eastern shore of the Adriatic.

Cipher used for secrecy

The sender used a homophone cipher, which allowed certain letters and words to be represented by multiple symbols. The letter contained 24 lines of code with nearly 1,300 marks using a repertoire of 155 signs.

Letter had been unsolved for years

The document had been listed among unsolved enigmas on the site Cryptiana for years, as no key was available to decode it. Its recent decryption marks a significant breakthrough in historical cryptography.