Engineer Says GPT-6 Astra Deciphered Napoleon's 217 Year Old Coded Letter

AI engineer Carter Church says he used OpenAI's GPT-6 Astra to decipher a coded letter Napoleon sent in 1809, according to 36Kr. Satoshi Tomokiyo, who operates the cryptography site Cryptiana, reviewed Church's code and verification scripts and said the cipher appeared solved, though the claim has not been independently peer reviewed.

Church gave Astra a low resolution black and white copy containing about 1,300 handwritten cipher units. The model grouped them into 155 symbols, combined an incomplete historical key with visible French text, and wrote a solver using simulated annealing and statistical patterns from nineteenth century French. The process took about six hours.

Church attempted the letter after Astra helped decode a previously unsolved Enigma message. For the Napoleon cipher, the model identified symbols representing both individual letters and complete words, then checked its reconstruction against the original image.

The decoded letter contains troop positions sent to Marshal Auguste de Marmont before the 1809 war with Austria. It also reconstructs a passage omitted from an 1865 collection of Napoleon's letters, in which Napoleon told Marmont not to be intimidated by a small number of enemy troops or "a gathering of rabble."