AI Decrypts 217-Year-Old Napoleon Era Wartime Letter

AI engineer Carter Church used OpenAI's GPT-6 Astra to decrypt a 217-year-old wartime letter from 1809 in approximately six hours. The missive, sent by Napoleon's stepson, Eugène, to Marshal Marmont, detailed French and allied troop positions two weeks before an Austrian invasion. Church achieved the breakthrough using a single prompt and a low-resolution scan from a 1969 French army journal, utilizing the AI to transcribe 1,300 symbols and locate a partial key table by historian Daniel Tant.

Satoshi Tomokiyo, maintainer of the Cryptiana list of unsolved ciphers, officially marked the letter as solved and noted that most of his listed puzzles have been cracked by AI since mid-September 2026. While Tomokiyo described the year as a turning point for the field, some historians, including Michael Rowe of King's College London, argued the decoded message provided no new historical information as the contents were already known through other correspondence.

This event is part of a broader trend of AI-driven historical research. Other large-scale projects include the virtual unrolling of the Herculaneum Papyri in Italy, the transcription of 14,600 Latin pages from Notre Dame Cathedral archives by Julie Claustre, and a project led by Daniel Stoekl Ben Ezra to transcribe 10 million pages of Hebrew manuscripts.