The secret code of King Charles V of Spain is deciphered after five centuries

A team of researchers has cracked a five-century-old code that reveals an alleged French plot to kill the Holy Roman Emperor, who was also King Charles V of Spain.

Charles was one of the most powerful men of the 16th century, presiding over a vast empire that conquered much of Western Europe and the Americas during a reign of more than 40 years.

It took the team from the Loria research laboratory in eastern France six months to decipher the letter written in 1547 by the emperor to his ambassador in France.

The tumultuous period saw a succession of wars and tensions between Spain and France, ruled at the time by Francis I, the Renaissance ruler who brought Leonardo da Vinci from Italy.

Charles V’s letter to Jean de Saint-Mauris was forgotten for centuries in the collections of the Stanislas library in Nancy.

Decipher the symbols

Cecile Pierrot, a cryptographer from Loria, first heard of it at a dinner party in 2019, and after much research was able to see it in 2021.

In painstaking computer-aided work, Pierrot found “distinct families” of some 120 symbols used by Charles V.

“Whole words are encrypted with a single symbol,” and the emperor replaced vowels following consonants with signs, he said, an inspiration that likely comes from Arabic.

In another obstacle, the king used symbols that mean nothing to mislead any opponent who tried to decipher the message.

The breakthrough came in June when Pierrot was able to make out a sentence in the letter with the king’s signature and the team then cracked the code with the help of historian Camille Desenclos.

“It was painstaking and time-consuming work, but there was really a breakthrough that happened in one day, where all of a sudden we had the right guess,” he said.

Another letter from Jean de Saint-Mauris also helped, in which the recipient had scrawled a form of transcription code in the margin.

Desenclos said it was “rare as a historian to be able to read a letter that no one had managed to read for five centuries”.

It “confirms the somewhat degraded state” in 1547 of relations between Francis I and Charles V, who had signed a peace treaty three years earlier, he said.

But relations were still tense between the two, with various attempts to undermine each other, he said. So much so that one nugget of information revealed was the rumor of a plot to assassinate Charles V that was said to be brewing in France, Desenclos said.

He said “not much was known” about the plot, but emphasized the “fear” of the monarch.

Researchers now hope to locate more letters between the emperor and his ambassador “to get a snapshot of Charles V’s strategy in Europe.”

“It is likely that we will make many more discoveries in the coming years,” added the historian.

Click on the video above to learn more.

Leave a Reply

Your email address will not be published. Required fields are marked *