A cybersecurity engineer used OpenAI’s GPT-6 Astra to decode a 217-year-old cipher letter tied to Napoleon Bonaparte, unlocking military orders unread since 1809.
Carter Church, an engineer at SentinelOne, broke a long-sealed message sent to French general Auguste de Marmont by Napoleon’s stepson Eugene, the Viceroy of Italy. The letter had sat unread for 217 years after its cipher key was lost.
Daily Mail reporting describes a 1809 dispatch that opens with one line of French, then runs 24 lines of two-digit numbers, stray letters, and invented symbols. Church fed a single image of the plate into GPT-6 Astra, the OpenAI model he used for the job, and the system finished the full multi-modal workflow in six hours.
On March 16, 1809, Napoleon wrote from Paris and told Eugene to get orders to Marmont. Marmont’s troops sat in Dalmatia, on the far side of the Adriatic. If war with Austria closed the gap, he risked isolation from every other French army. The letter was meant to fix that.
Church said the feat was less about raw codebreaking than about speed and reach. Specialists could have solved the cipher with enough time. The grind of transcription, cataloging, translation, and cracking is what stalled it.
He explained the run this way:
Church wrote:
"I used GPT, 6 Astra to break an unsolved cipher to one of Napoleon's generals that had gone unread for 217 years. What makes this impressive isn't actually the codebreaking, but that Astra completed the entire multi-modal workflow in six hours from a single image and goal."
The model sliced a 1,202-by-1,836 plate into rows, read the marks, and judged which of 175 hand-drawn signs were the same character written twice. Only then did it break the code.
Church put it plainly:
"Astra cut the 1,202 by 1,836 plate into rows, read the signs, decided which of 175 hand, drawn marks were the same sign written twice, and only then began breaking the cipher."
He added that the cipher itself was not hard. Cryptographers could have cracked it with time and energy. The bottleneck was the messy, multi-step labor around it.
"The cipher itself isn't difficult, and cryptographers could have cracked this easily given the time/energy," he said. "But, the work to transcribe, catalog, translate, then crack is involved and multi-disciplinary."
The recovered text speaks in Eugene’s voice and carries the instructions Napoleon charged him to deliver. It starts by confirming earlier traffic.
The letter opens:
"You must have received, General Marmont, my letters of the 8th, 14th, and 20th of this month."
Those earlier notes held the core orders. The newly read message then lays out where French and allied forces stood and tells Marmont what to expect when the march order came.
The decoded passage states:
"[Those letters] contained the orders and instructions which [His Majesty] charged me to give you. I hasten today to acquaint you with the disposition of French and allied armies. The Duke of Danzig, at the head of forty thousand Bavarians, occupies Munich and Passau. Prince Poniatowski, at the head of thirty thousand Poles, is camped on the Vistula, threatening Cracow. The Prince of Ponte-Corvo commands the Saxon army, camped in front of Dresden, and the Duke of Auerstaedt occupies Bayreuth with eighty thousand French troops. The Duke of Rivoli commands sixty thousand men quartered at Ulm and Donauwörth. [General] Oudinot, with the elite corps comprising forty thousand men, is at Augsburg and along the Lech."
Force counts and places stack up fast: 40,000 Bavarians at Munich and Passau; 30,000 Poles on the Vistula; 80,000 French at Bayreuth; 60,000 at Ulm and Donauwörth; 40,000 elite troops at Augsburg and along the Lech. The army of Friuli is listed at 80,000, with the Dalmatian corps and rear reserves still to add.
The message turns from order of battle to pressure on Austria, and to Marmont’s nerve.
It continues:
"The Russians are marching against Austria, and the army [of] Friuli today numbers eighty thousand men. Add the Dalmatian corps, without counting the reserves being organised everywhere in the rear, and you see that Austria will be attacked at once on every side. She is consequently hastening toward her ruin. When you receive the order to march, you must not allow yourself to be intimidated by a few troops or a gathering of rabble."
Eugene also reports Austrian positions and doubts about enemy plans. Austrians remain at Laybach, Klagenfurth, Villach, and Salzburg and appear to threaten the Tyrol by way of Lintz. They may also shift men into Galicia against the Russians. Militia have been called up. Efforts to stir the public have not yet proved they will much reinforce the army. Nothing, the letter says, is fully settled.
The close is impatient and practical:
"I continue to await news from you with impatience. The Austrians are still at Laybach, Klagenfurth, Villach and Salzburg, and appear to threaten the Tyrol by way of Lintz. Yet one would think that they are considering sending troops into Galicia to oppose the Russians. These dispositions would suggest that their campaign plan has been upset before war has even been declared. There is, however, still nothing definite. The militia have been called into active service, and although efforts have been made to excite people, it has not yet been proved that these levies will provide much reinforcement for the army."
In plain terms, Paris wanted Marmont briefed, steady, and ready. The lost key left that order dark for more than two centuries.
Church’s larger point was not romance about Napoleon. It was about work that sits untouched because it is narrow, tedious, and cross-field.
He argued every field carries an unsolved pile of niche problems specialists lack bandwidth to touch. The people shrinking those lists, he said, will more often be outsiders who got curious and moved.
"Every field has an unsolved backlog of niche problems that specialists don't have the bandwidth to tackle," Church wrote. "The takeaway here is that the people shortening those lists will increasingly be outsiders who were simply curious."
That is the live wire in the story. A cybersecurity engineer, a single image, and a capable model did in one workday what a lost key and institutional inertia left sealed since the year before Napoleon’s later wars closed at Waterloo. Clear orders. Real troop numbers. A general told not to scare. History did not need another committee. It needed someone willing to open the file.
Useful tools in private hands beat dusty backlogs every time, especially when curiosity shows up for work.
