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AI decodes Napoleon letter after 217 years
A lost military cipher has yielded a message about Napoleon’s planned war against Austria.
What happened
An AI engineer used OpenAI’s GPT-6 Astra to transcribe and decode a military letter sent in 1809 on Napoleon Bonaparte’s instructions to General Auguste de Marmont. The recovered text concerns French and Austrian troop movements before France’s war with Austria. A historical-cipher specialist reviewed the solution.
Numbers
- 217 yearsTime the message remained unread — Sent in 1809
- 1,300 signsCharacters in the encoded message — Included letters and symbols
- 6 hoursModel runtime for the decoding — From a single image
Questions
- Who actually dispatched the letter?
- Eugène de Beauharnais, Napoleon’s stepson, sent it from his headquarters on the emperor’s instructions to Marmont, then serving in Dalmatia.
- How was the code reconstructed?
- The model transcribed an image, used previously identified character values, tested candidate words, and compared results with surviving Marmont writing.
- Why was AI useful here?
- The lost cipher required many word combinations; automated trial and comparison completed work no cryptographer had previously accomplished by hand.
- Who checked the decoded result?
- Patent engineer and historical-cipher specialist Satoshi Tomokiyo reviewed the solution after Church published his account of the process.
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The catch
The coverage does not publish a complete transcription or detail how every passage was historically verified.
Independent review was reported.