French scientists deciphered a coded letter signed in 1547 by the most powerful ruler in Europe, who revealed that he constantly feared an assassination attempt by an Italian mercenary.
The letter, sent by Charles V of the Holy Roman Empire to his envoy at the French royal court, Jean de Saint-Mauris, provides insight into the concerns of Europe’s rulers at a period of hazardous instability brought on by religious wars and competing strategic interests.
For historians, it is also a rare opportunity to observe the shadowy side of diplomacy in action; deception, secrecy, and smirking insincerity all seemed to be prevalent at the time.
The letter’s existence was initially reported to the cryptographer Cecile Pierrot three years ago during a dinner party in Nancy. She eventually located it in the city’s historic library’s basement after extensive study.
She gave herself the challenge to decode the document within a few days, and she was surprised to discover that the work was more difficult than she anticipated.
The three-page letter, which has around 70 lines and 120 encrypted symbols, is primarily written in plain current French in three portions.
“The initial step was classifying the symbols and searching for patterns. But it was much more complicated than just one symbol standing in for one letter “Pierrot” says.
She and her crew started to advance gradually. She discovered there were two different kinds of symbols: basic and sophisticated. In most cases, vowels were added as diacritical markings, much like in Arabic, rather than being represented as letters. Despite not having a diacritical mark, the vowel “e” was generally gone.
Additionally, they discovered that while the majority of symbols indicated individual letters or groups of letters, some also stood in for entire words, such as the needle for English King Henry VIII. Additionally, several symbols appeared to serve no purpose at all.
When historian Camille Desenclos alerted the crew to other coded communications to and from the emperor, a breakthrough finally occurred. The recipient had made an impromptu translation on one of these, which was retained at Besançon.
Pierrot refers to the inscriptions that aid in the decipherment of Egyptian hieroglyphics as “our Rosetta Stone.” “The key was in there. Even though it saved a tremendous amount of time, we would have eventually arrived otherwise.”
The rarity of the letter ‘e’ is a sign that the code makers knew their stuff. Because ‘e’ is the most common letter (in old as in modern French), it is what codebreakers would be looking for first. And the fake symbols were simply put in to sow more confusion.
“Of course by today’s standards it is pretty basic,” says Pierrot, who spends her normal time thinking about quantum physics and massive prime numbers. “But given the tools they had, they certainly put us to work!”
So what is in the letter?
The team has not yet issued a full translation, which they are saving for an academic paper. But this week they set out the themes.
February 1547 was a time of rare relative peace between the rival powers of France and the Holy Roman Empire. Emperor Charles V – ruler of vast areas including Spain, the Netherlands, Austro-Hungary, and southern Italy – was no longer actually at war with King Francois I. But mistrust still prevailed.
Two recent events were in both rulers’ minds. The first was the death of Henry VIII just a few weeks before. And the second was the rebellion in Germany by a Protestant alliance called the Schmalkaldic League.
In the letter, Charles V reveals his concern to maintain peace with France so that he can focus his forces against the League. He tells the ambassador to keep himself abreast of thinking in the French court, in particular any reaction to the death of King Henry.
What he wants to avoid above all is the French and English combining to lend more assistance to the Protestant rebels.
Charles V then speaks of a rumor which is circulating – that he, the emperor, is to be the target of an assassination attempt by the Italian condottiere (mercenary leader) Pierre Strozzi. Saint-Mauris is to find out as much as he can about this story. Is it just gossip, or a genuine threat?
And finally, in the longest part of the letter, Charles V sets out for his ambassador the current state of play in his campaign against the League. There has been a new outbreak of rebellion in Prague, and the emperor’s nephew Ferdinand of Tyrol has been forced to flee.
But Charles V gives instructions on how Saint-Mauris is to “spin” the news at the French court. The Prague rebellion is a minor affair, he is told to say, and Ferdinand has left the city because he wants to join his father – the emperor’s brother – on the campaign.
For the historian Camille Desenclos, the fact that some parts of the letter are encrypted and others are not significant.
“They all knew there was one chance in two that the letter would be intercepted. In which case there were messages that were worth passing to the French,” she says – like the fact that the emperor was cooperating on confidence-building measures in northern Italy.
“These were left in plain language. But there were other matters that had to stay secret – like the true state of affairs with the Protestant rebellion, and they were put into code.”
What happened next? The French monarch François I passed away just a few weeks later, and his son Henri II succeeded him. The following year, Charles V destroyed the League, but Protestantism remained in Germany. Henri II and the Protestant lords forged a fresh coalition in 1552 to oppose the emperor.
Additionally, there was no attempt at murder. In 1558, Charles V passed away in a monastery in Spain.