The document is dated to the spring of 1809, when France was preparing for yet another war with the Austrian Empire. The message was intended for General Auguste de Marmont, who commanded the French troops in Dalmatia. After a short introduction in French, there followed 24 lines of encrypted text — approximately 1300 digits, letters, and handwritten symbols. The key necessary to read the message was lost back in the 19th century. The method of encryption itself posed additional challenges. The document used a homophonic system: one letter could be represented by several different symbols, and some signs corresponded to entire words or the names of military leaders. Moreover, the surviving copy of the document was of low quality, making it difficult to even recognize some symbols. American engineer Carter Church took on the task of decryption. He combined the capabilities of neural networks with statistical language analysis. The system first recognized the handwritten symbols and then began searching for possible matches, taking into account the French military vocabulary of the Napoleonic era. As a result, the algorithm managed to reconstruct the encryption system and read the content of the dispatch. It turned out that the document contained information about the locations of the corps of Marshals Louis-Nicolas Davout, André Masséna, Jean-Baptiste Bernadotte, and François Joseph Lefebvre on the eve of the War of the Fifth Coalition. The message also mentioned the movements of Russian troops and the redeployment of certain French units. The information obtained allowed researchers to clarify some events of March 1809 and supplement the information contained in Napoleon's memoirs. Thus, a document that had remained closed to researchers for 217 years was read in just a few hours — thanks to technologies capable of finding patterns in historical ciphers and working with archival materials that were considered practically undecipherable.
