Breaking the Cipher of the Napoleonic war briefing, unread for 217 years
6 hours ago
- A letter to General Marmont, encrypted and unread for 217 years, was finally deciphered using AI tools like GPT-6 Astra.
- The cipher was a homophonic substitution code with 155 distinct signs; only 33 letter values were previously known.
- The solution process combined transcription, simulated annealing, and cross-referencing with Napoleonic texts, producing a full reading from a single scanned plate.
- The decrypted letter, dated to March 1809, listed French and allied army positions and was a forecast of the upcoming war with Austria.
- The letter's predictions matched historical events (e.g., Austrian troop positions and the Russian response), showing the accuracy of Napoleon's intelligence.
- This breakthrough demonstrates how modern AI can rapidly solve historical ciphers that were previously considered unsolvable by human specialists.