By Peter Leadbetter
Author of The Perfect Militia, The Stuart Trained Bands of England and Wales, 1603-1642, Peter Leadbetter writes about some research he is currently undertaking on cyphers and codes used during the British Civil Wars.
In days before electronic communications, the written word reigned supreme. One problem in the Civil War was getting that written word from the sender to the recipient, safely. Then as now, communications were being intercepted and read by the other side, something which neither side could prevent. Methods to improve the arrival rate were used, multiple letters being sent, carried by different messengers being one. The main problem was that if a letter fell into enemy hands they could read what had been written. A number of solutions were used to prevent or slow down this compromising situation were used. Invisible ink was one where an innocent letter would be written in ordinary ink and a secret one written between the lines using lemon juice or similar fluid, literally, “reading between the lines”. The most common method used however was ciphers and codes, the more common of these being ciphers.
To use a cipher, the people concerned had first to ensure that the recipient had a copy of the cipher, there is at least one case where, post Naseby, King Charles had to borrow a cipher because he did not have one that the recipient could use. That done the letter could be written and then enciphered. Usually only parts of the letter would be in cipher, it is rare for a whole letter to be enciphered. One problem I have encountered with these letters is mistakes made when the letter was being enciphered. Usually it’s a simple case of looking at the decipherment table and looking at cells either side or above or below to get the correct value.
If or when these letters were intercepted, it was a case of how long would it take to decipher them. In some cases the answer is never, other cases, a few weeks and some, the next day. The time taken depended on the complexity of the cipher used and the amount of enciphered material that was available, the more the better. The problem at this point was whether the contents were worth the effort in deciphering them. Imagine spending 2 weeks deciphering a letter to find out that it concerned events that had already taken place during those 2 weeks. The question to ask is, did anything useful come out of that effort. The answer is yes. If a cipher has been broken, it means that the next time it is used a letter can be deciphered in a very short space of time. A particular cipher was usually used by a very small group of people, that group could be identified from their use of that particular cipher, another useful outcome.
So what did the ciphers look like? The most common form was the use of dinomes, 1 or 2 figures representing a single letter, actual numbers were spelt out and not enciphered. One oddity here is that the alphabet used was often shorter than the official alphabet. The letters i and j were basically interchangeable and so usually only the letter i was used, the same applied to the letters u and v and finally the letter z was rarely used and so was sometimes not included.. This meant that the alphabet used was often only 23 letters long and not 26. Please note the use of the words usually, often and rarely. Usually the numbers 1 to 90 were used for the letters with letters being assigned 2, 3 or 4 values to make the system more secure. Two other forms were often seen, these were digraphs, a letter and a number and trinomes, 3 numbers. The digraphs usually represented a short word, at, is and was, or a syllable, ing, ly or pre for example. The trinomes would be used for longer words, nouns, places or people. A cipher system could use 1, 2 or all 3 of these forms.
Codes, as mentioned, were also used. These were far more complex and involved replacing each word or a number of words in a document with another word. So for example, King Charles could be referred to as Mr Smith, Prince Rupert, Mr Brown, London could be France and Oxford could be Germany. Codes are far more complex than the ciphers which were used.
In my research I have been focussing on reconstructing the cipher tables and to date have 31 useable tables which I am adding to as my research continues. I am using these to re-examine the deciphered documents held in various archives and as well as gaining more data I am also, in a number of cases, correcting the original decryptions. I am also looking at the documents that were not decrypted during the Civil War. There are not many of these.
Finally, I am also be looking at the men who did this work at the time. Many of these men are unknown to us today and yet their contributions to the war efforts of whichever of the parties that they worked for needs to be made known.
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