TOKYO, Oct 16 — Napoleon Bonaparte ordered a wartime message written in code, creating a puzzle that remained unsolved for more than 200 years — until artificial intelligence cracked it in a matter of hours.

AI is helping non-specialists unlock the secrets of historical sources, a development described as a “turning point” in a field previously dominated by scholars and dedicated hobbyists.

One new sleuth is Carter Church, a 27-year-old AI engineer who deciphered a 19th-century letter to one of Napoleon’s generals.

Without digital tools, the task could have taken weeks, but the latest model from ChatGPT-maker OpenAI broke the cipher in just six hours.

“What AI mostly brings is persistence,” Church told AFP, saying he felt “an unbelievable sense of satisfaction and excitement when I saw the result”.

The message, dating from 1809, detailed the positions of French and allied troops in two dozen lines of symbols, numbers and letters, but had been left untouched in an online academic archive.

Traditional, low-tech methods of cracking ciphers are effective but time-consuming and labour-intensive, meaning historians “have more important problems to solve, so many ciphers like this often sit unattended”, Church said.

Church, who works at US cybersecurity firm SentinelOne, needed to learn “very little” about code-breaking techniques or the historical period to solve the puzzle.

After spending several evenings working on it, he consulted Japanese patent engineer Satoshi Tomokiyo, who maintains an online list of unsolved ciphers, to verify the solution.

“2026 will be remembered as a turning point for codebreaking of historical ciphers,” Tomokiyo wrote on his website Cryptiana, a go-to resource for the small but enthusiastic global community of amateur cryptographers.

‘Mixed feelings’ 

Researchers had already been developing AI models to crack ciphers, but the public release of advanced general-purpose tools has unleashed a wave of new solutions.

Although Church used OpenAI’s most powerful model, GPT-6 Astra, others have turned to leading offerings from rival US AI company Anthropic.

Tomokiyo said that since mid-September, AI had been used to crack most of the ciphers on his list.

“There remain some tough problems” that could stay unsolved for years because there is less relevant data available to help AI decipher them, the 58-year-old told AFP.

“I’m excited long-time problems are now solved, but on the other hand, I have mixed feelings, because AI seems to have solved these difficult problems so easily,” he said.

As the technology threatens to take away the satisfaction of being the first to crack a cipher, one fellow code-breaker told Tomokiyo: “I feel useless.”

AI is surpassing human abilities in fields ranging from mathematics to computer programming, while threatening to transform or even eliminate many jobs.

The technology is also changing historical research beyond code-breaking, helping researchers analyse millions of medieval manuscripts and decipher ancient scrolls.

The Herculaneum Papyri – hundreds of papyrus scrolls carbonised by the eruption of Mount Vesuvius in AD 79 – are too fragile to be unrolled without risking their destruction.

Researchers are now using X-rays and AI to reveal the hidden writing inside them.

In June, researchers in Italy announced the first complete virtual unrolling of a scroll, which turned out to contain a treatise on ethics.

‘Facebook of the past’ 

AI is also being used to build a vast, searchable collection of previously inaccessible sources on Jewish history and culture by transcribing 10 million pages of Hebrew manuscripts.

“It’s gigantic. No human being could process such a quantity of data,” said project leader Daniel Stoekl Ben Ezra of the École Pratique des Hautes Études in Paris.

Researchers hope databases built from the digitised texts – which he likens to a “huge Facebook of the past” – will help uncover connections between people, places and ideas.

At Notre-Dame Cathedral in Paris, an AI system has been trained to transcribe 14,600 pages of Latin from the church’s medieval archives, a task that also involves deciphering difficult historical writing.

“These are minutes drawn up by notaries who abbreviate their decisions. The script is highly administrative, very pragmatic... with rather technical vocabulary,” said historian Julie Claustre, who leads the e-NDP project.

With character recognition rates ranging from 88 to 94 per cent, the project has revealed information about the cathedral’s daily life, construction work, staff and care of abandoned children.

Doing the same work by hand would take “several decades”, Claustre said, adding that the benefits went beyond saving time.

Automation enables “inquiries that were not previously possible; it transforms the conditions of research”. — AFP