A 108-year-old encrypted WW1 German radio message has been deciphered with the help of ChatGPT-6 Astra. The cipher, which was never cracked before, was solved by AI developer Prinz, who posted the achievement on their Substack.
The message was sent to the German High Command in 1918 and was part of a famous list of fifty unsolved ciphers kept on the German science blogging portal Scienceblogs.de. It used a convoluted grid of letters that shuffled depending on the current keyword.
Prinz Picked the Code
Prinz chose the code from that list, which makes this a notable solve among a set of fifty that have remained open for decades. The developer then fed the encrypted text into GPT-6 Astra, the powerful AI model released by OpenAI on September 3, 2026.
The Tool’s Previous Work
Astra played Minecraft autonomously before this, and it was also used to build a simulation within a simulation. Now it has shown code-breaking ability.
The Keyword That Cracked It
Astra used the word “TRUPPENVERSCHIEBUNG” as the key to solve the cipher. The decoded message, when translated into English, was a radio alert that read: “AN ENGLISH CRUISER ARRIVED AT SEVASTOPOL ON THE ?4TH AN ALLIED SQUADRON FOLLOWS ON THE 26TH.”
The original German text read: “EIN ENGLISCHER KREUZER EINLIEG X SEWASTOPOL X S4STEN X EIN GESCHWADER DER X ALLIIERTEN FOLGT 26STEN X.” Prinz posted the solve on September 17, 2026, with the message “GPT-6 Astra deciphered a 1918 German radio transmission that, to my knowledge, has never been deciphered before.”
The Message’s Content
The message reported that an English cruiser arrived at Sevastopol on November 24, 1918. It also said that an Allied squadron followed on November 26.
The ‘?’ in the date was likely a typo made in transmission. The cruiser’s arrival time aligned with the arrival of British cruiser HMS Canterbury in Sevastopol, Crimea, on November 24, 1918. The Allied squadron’s arrival was on November 26, aligning perfectly.
Astra’s Check Against Military Logs
Prinz’s solve shows that modern AI models can tackle these problems with surprising effectiveness. The model was able to take an encrypted message and a known list of unsolved ciphers, find the right keyword, and produce a translation that matched real historical events.
The Cipher’s Difficulty
The Germans used a convoluted grid of letters in 1918 that shuffled depending on the current keyword. That kind of system is hard to crack without knowing the keyword.
“GPT-6 Astra deciphered a 1918 German radio transmission that, to my knowledge, has never been deciphered before.”
Prinz’s solve moves a fifty-year-old list of unsolved ciphers down to forty-nine. The decoded text matched the arrival of HMS Canterbury and the Allied squadron.
The Message’s Recipient
The message was addressed to the German High Command, perhaps for the eyes of a Naval Command officer or admiral. The Germans were using a system of shuffled letters that depended on a current keyword.
Key Facts Box
- Cipher: 108 years old, sent in 1918, never cracked before
- AI model: GPT-6 Astra, released September 3, 2026
- Keyword: “TRUPPENVERSCHIEBUNG”
- Decoded message: “AN ENGLISH CRUISER ARRIVED AT SEVASTOPOL ON THE ?4TH AN ALLIED SQUADRON FOLLOWS ON THE 26TH”
- Cruiser: HMS Canterbury, British, arrived November 24, 1918
- Squadron: Allied, arrived November 26, 1918
- Source: Prinz, posted on their Substack, September 17, 2026
The solve is a victory for AI, for history, and for the developer who made it happen. The cipher was cracked, and the message was read.
The decoded message shows that the Germans were tracking Allied movements in real time. The cruiser’s arrival and the squadron’s follow-up were both recorded in the message, and the decoded text matched the arrival dates of HMS Canterbury and the Allied squadron.
Source material: “AI developer uses GPT-6 Astra to crack 108-year-old WW1 code,” Dexerto.
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