Archaeology & History

Mysterious coded Napoleon letter has been cracked after 217 years

By T.K. Randall
October 3, 2026

Image: AI-generated (Midjourney) More than two centuries after it was originally written, the contents of a mysterious coded letter have finally been revealed thanks to the capabilities of one of the latest artificial intelligence models.

Penned by Napoleon Bonaparte, the letter had been sent to French general Auguste de Marmont in 1809 by the Viceroy of Italy (who happened to be Napoleon's stepson).

It begins in clear French, but then the rest of the letter is written in a strange code consisting of numbers, letters and inverted symbols.

Originally, a key would have been used to decipher it, but this had been lost long ago, meaning that nobody had ever been able to actually decode the message and find out what it says.

Now, though, cybersecurity engineer Carter Church has finally found a way to decipher the mysterious letter using artificial intelligence.The deciphering process, which used GPT-6 Astra, took a mere 6 hours.

The decoded letter had given General Marmont a strategic overview of the positions and strength of French and allied armies, along with information about Austrian forces.

It also urged Marmont to prepare to march without being intimidated by relatively small enemy forces, saying that Austria was about to be attacked from all sides and was "hastening towards her ruin."

"I used GPT-6 Astra to break an unsolved cipher to one of Napoleon's generals that had gone unread for 217 years," Church wrote on X.

"What makes this impressive isn't actually the codebreaking, but that Astra completed the entire multi-modal workflow in six hours from a single image and goal."

Source: Mail Online

Tags: Napoleon, Code