Artificial intelligence deciphers Napoleon's encrypted letter after more than 200 years

A mysterious letter written by Napoleon Bonaparte more than 200 years ago has been deciphered for the first time thanks to the use of artificial intelligence (AI).

The letter, written by the emperor, was sent to the French general Auguste de Marmont by Napoleon's stepson Eugene, viceroy of Italy, in 1809. The first line is written in French, but the next 24 lines consist of two-digit numbers, single letters and invented symbols.

Although the letter originally came with a guide to deciphering it, this was long lost, meaning its contents have been a mystery for decades.

Now, Carter Church, an engineer at the cybersecurity company SentinelOne, has deciphered the code using artificial intelligence, as reported by the Daily Mail.

"I used GPT-6 Astra to crack an unsolved code from one of Napoleon's generals that had remained unread for 217 years. What's impressive is not the decryption itself, but that Astra completed the entire multimodal workflow in six hours from a single image and a single target," says Church.

On March 16, 1809, Napoleon wrote from Paris to his stepson Eugene, asking him to send a letter to Auguste de Marmont, a friend of the emperor, whose troops were stationed in Dalmatia (Croatia), on the other side of the Adriatic.

Once deciphered, it has been revealed that the letter details the location of all other French and Allied armies, and urges Marmont to "not be intimidated" by his isolated position.

"The encryption itself is not difficult, and cryptographers could have easily cracked it if they had the time and energy," Church says. "But the work of transcribing, cataloguing, translating and then deciphering is complex and multidisciplinary," he adds.

"Each field has a host of unsolved problems in specific market niches, problems that specialists do not have the capacity to address," continues the expert.