AI Decodes Napoleon’s Secret Battlefield Message After 217 Years

An encoded military letter containing orders from Napoleon to one of his generals has been deciphered after 217 years by AI.The letter, addressed to General Auguste de Marmont in March 1809, was cracked in six hours by an AI engineer using OpenAI’s GPT-6 Astra. Carter Church broke the cipher from a scanned image of the letter that was sent less than two weeks before Austria began a new war against Napoleon by invading Bavaria.The letter had survived only as a reproduction published in a French military journal in 1969. No complete transcription existed, and most of its code had never been deciphered.Mr. Church gave Astra the image and had it work through the process largely on its own. The model divided the document into rows, distinguished between handwritten symbols, transcribed roughly 1,300 cipher units and then began trying to reconstruct their meaning.Only 33 values in the cipher had previously been published, accounting for about a third of the document. Astra had to work out most of the rest. It eventually reconstructed a key covering 155 distinct signs, including symbols that represented entire French words. What emerged was a military briefing intended for Marmont, whose roughly 13,000 troops were stationed in Dalmatia and separated from Napoleon’s other armies by Austrian territory.According to Mr. Church’s English translation, the letter told Marmont “I hasten today to acquaint you with the disposition of French and allied armies.”The letter laid out the positions of French and allied forces around Europe. It said 40,000 Bavarians occupied Munich and Passau, 30,000 Polish troops were threatening Krakow, and tens of thousands of French troops were stationed around Bayreuth, Ulm, Donauwörth and Augsburg.“The Russians are marching against Austria,” the message also claimed, before telling Marmont that Austria would soon be attacked across multiple fronts. It warned that Austria was moving “towards its ruin.”The letter then told Marmont to “Add the Dalmatian corps” to the forces being counted against Austria. It said Austrian troops “appear to threaten the Tyrol,” but cautioned, “There is, however, still nothing definite.” It also noted that “The militia have been called into active service,” while questioning how much those new forces would actually reinforce the Austrian army.The message closes with another direct appeal to the isolated general, “I continue to await news from you with impatience.”The decoded message closely follows an order Napoleon sent his stepson, Eugène de Beauharnais, on March 16, 1809. Napoleon instructed him to send Marmont a ciphered letter explaining where the French and allied armies were positioned.The newly decoded document lists the same forces in the same order and with the same troop numbers, providing another check on the reading. Mr. Church also reran the cipher-solving process without Napoleonic texts in the language data used by the solver and said it recovered the same reading.The Napoleon letter is only one example of what researchers say has become a sudden wave of AI-assisted historical codebreaking.George Lasry, a researcher who specializes in historical cryptography, told The New York Sun that the Napoleon letter deception is “far from being the only or most interesting” recent achievement involving AI and old ciphers.Mr Lasry says large language models solved more than 40 historical ciphers in September, working in an autonomous setup developed by data scientist Dan Bourdeau. In 24 cases, the models reconstructed keys using only the ciphertext. In others, AI agents searched archives and databases for possible keys, plaintexts or other clues. Some involve major historical figures.AI systems reconstructed encrypted letters sent in 1585 and 1586 by Henry of Navarre, the future King Henry IV of France, to an envoy helping raise a German army. Lasry had independently solved those letters earlier but had not published his solution, allowing the results to be compared. Another project decoded a 1916 telegram associated with the circle of Chinese revolutionary Sun Yat-sen, then expanded the work to roughly 60 intercepted messages. One reported the assassination of revolutionary Chen Qimei. The new systems are not always simply “cracking” codes. Sometimes they are doing something closer to historical detective work, searching enormous archives, identifying related documents and testing clues before turning to cryptanalysis.Mr. Lasry and Mr. Bourdeau are now studying why the models have suddenly become so effective, including whether their advantage comes from stronger reasoning or simply their ability to search, test hypotheses and repeat tedious work at a speed no human cryptanalyst could match. For historians, that raises a possibility that thousands of encrypted documents that have spent centuries sitting unread in archives may no longer stay that way.

AI Decodes Napoleon’s Secret Battlefield Message After 217 Years

AI Decodes Napoleon’s Secret Battlefield Message After 217 Years

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