AI engineer Carter Church used GPT-6 Astra to decipher a secret 217-year-old letter on October 5, 2026. The message from Napoleon’s stepson to General Marmont remained a mystery until AI cracked the code in six hours. Zack White said, "This is a really interesting use of artificial intelligence."
A coded, secret wartime letter. Over two centuries old. It was a hearteningly baffling mystery -- until AI made light of it.
It was written and sent by Eugène de Beauharnais, a stepson of Napoleon, to General Auguste de Marmont, informing him of the Napoleonic forces arrayed against the enemy -- Austria. The letter was preserved, but not the code. So it remained undeciphered for 217 years.
Carter Church, an AI engineer at cybersecurity company SentinelOne, used OpenAI's GPT-6 Astra to decipher the coded military message.
The letter was a cryptographer's nightmare. It contained about 1,300 coded elements, made up of 155 different signs. A historian had identified the meaning of 33 symbols, but it still left much of the message shrouded in secrecy.
But GPT-6 Astra, as one can imagine, laughed lightly at it. It handed Church the neat English version in six hours. Astra first read the handwriting, then connected the letter to an existing partial code table. It went on to develop a computational method, called 'Simulated annealing', testing possible symbol values against patterns in the French language. Historical writings helped check whether the resulting text made sense. Its achievement went beyond unlocking an old message. It signified the triumph of the collaboration of handwriting recognition, historical research, cryptanalysis and computer programming in one workflow.
"This is a really interesting use of artificial intelligence... to try and provide a credible solution to a historical mystery," Zack White, a history research fellow at the University of Portsmouth and the host of the Napoleonic Wars Podcast, told Live Science.