AI tool cracks 217-year-old Napoleon cipher revealing troop plans

A 217-year-old ciphered correspondence from Napoleon Bonaparte to his senior general Auguste de Marmont has been finally decoded by artificial intelligence. Carter Church, an AI engineer at SentinelOne, applied OpenAI’s GPT-6 Astra system, spending six hours transcribing 1300 characters and using simulated annealing to align the output with Marmont’s known handwriting. The note, originally dispatched by Napoleon’s stepson Eugène in 1809, reveals detailed French and Austrian troop deployments on the eve of war and urges Marmont to advance without fear.

The breakthrough follows a prior AI success in cracking a 1941 German army message within ten hours. Researchers note the growing capability of AI to solve complex ciphers, raising both historical insights and privacy concerns. The decoded information sheds light on the strategic context that led to the French victory at the Battle of Wagram, after which Marmont was promoted to Marshal.