AI Deciphers Napoleon's Secret Code After 217 Years

A coded letter penned by Napoleon Bonaparte's stepson in 1809, containing crucial military information, has been deciphered after 217 years using artificial intelligence. The letter, sent by Eugene, Viceroy of Italy, to General Auguste de Marmont, was written amidst France's ongoing conflict with Austria.

At the time of its writing, Marmont, a close associate of Napoleon, was stationed in Dalmatia, isolated from French forces and allies. The correspondence began in French but quickly transitioned into an indecipherable mix of symbols, letters, and numbers, presumably intended to be understood with a lost deciphering key.

Carter Church, an engineer at cybersecurity firm SentinelOne, utilized AI, specifically GPT-6 Astra, to crack the centuries-old code. The process, from image input to decipherment, reportedly took the AI approximately six hours.

The initial deciphered line reads: “Vous avez dû recevoir, Monsieur le Général Marmont, mes lettres des 8, 14 et 20 courant,” which translates to: “You must have received, General Marmont, my letters of the 8th, 14th, and 20th of this month.”

The AI revealed that the remainder of the coded message detailed the positions of French and allied armies and urged Marmont not to be intimidated by his isolated situation. It stated, “The Russians are marching against Austria, and the army [of] Friuli today numbers eighty thousand men.” The letter further advised, “Add the Dalmatian corps, without counting the reserves being organized everywhere in the rear, and you see that Austria will be attacked at once on every side. She is consequently hastening toward her ruin.” It also included instructions: “When you receive the order to march, you must not allow yourself to be intimidated by a few troops or a gathering of rabble.” Napoleon also expressed his eagerness for updates, stating, “I continue to await news from you with impatience.”

This historical decryption comes in the context of significant military campaigns. Just two months after the letter was sent, Napoleon suffered his first personal defeat at the Battle of Aspern-Essling near Vienna, Austria, on May 21, 1809, resulting in substantial French casualties. However, Napoleon regrouped and subsequently defeated Archduke Charles in July of 1809 at the Battle of Wagram, a victory that led to the dissolution of the Fifth Coalition, an alliance against France.

Church commented that while the cipher itself was not inherently complex, the transcription, cataloging, and translation process would have been time-consuming for human cryptographers. He suggested that such complex, multi-disciplinary tasks are increasingly being tackled by individuals with novel approaches and specialized tools, like AI, driven by curiosity.