A team of researchers has cracked a five-century-old code that reveals an alleged French plot to assassinate the Roman Emperor and King of Spain, Charles V.
Charles was one of the most powerful men of the 16th century, presiding over a vast empire that occupied much of western Europe and the Americas for a reign of more than 40 years.
It took the team at the Loria research laboratory in eastern France six months to decipher the letter that the emperor wrote to his ambassador in France in 1547. The turbulent period saw a series of wars and tensions between Spain and France, then ruled by Francis I, the Renaissance ruler who brought Leonardo da Vinci from Italy.
Charles V’s letter to Jean de Saint-Mauris had languished for centuries in the collections of the Stanislas Library in Nancy, forgotten. Cécile Pierrot, a cryptographer from the Loria lab, first heard of its existence over dinner in 2019, and after much searching she was able to see it in 2021.
It bore the signature of Charles V and is at the same time mysterious and completely incomprehensible, she told reporters on Wednesday.
Cécile Pierrot (L) and Senior Lecturer in Modern History Camille Desenclos (R) explain the process of decrypting an encrypted letter from Charles V. Photo: Jean-Christophe Verhaegen/AFP/Getty ImagesThrough painstaking computer-assisted work, Pierrot found “different families” of about 120 symbols used by Charles V. “Whole words are enciphered with a single symbol,” and the emperor replaced vowels that came after consonants with characters, she said, an inspiration that would likely come from Arabic.
At another obstacle, he used meaningless symbols to mislead any opponent trying to decipher the message.
The breakthrough came in June when Pierrot managed to decipher a sentence in the letter and the team then cracked the code with the help of Camille Desenclos, a historian. “It was painstaking and tedious work, but there was really a breakthrough that happened in one day when we suddenly had the right hypothesis,” she said.
Another letter from Jean de Saint-Mauris, in which the recipient had scrawled some sort of transcription code in the margin, also helped.
Desenclos said it was “rare as a historian to read a letter that no one has been able to read for five centuries”. It “confirms the somewhat decrepit state” of relations between Francis I and Charles V in 1547, who had signed a peace treaty three years earlier, she said.
Relations between the two have been strained, with various attempts to weaken each other. So much so that a nugget of information was the rumor of an assassination attempt against Charles V, said to have been brewed in France, Desenclos said. “Not much is known” about the conspiracy, but it underscores the monarch’s fear, she said.
The researchers now hope to identify more letters between the emperor and his ambassador “to have a snapshot of Charles V’s strategy in Europe.”
“It is likely that we will make many more discoveries in the coming years,” added Desenclos.