by Barbara Bond
For your private information, we are very glad to tell you that your son is continuing to do the most valuable work.
The seriousness of this work was then reinforced by the following message;
Please do not show this letter to anyone outside the immediate family circle, and remember to burn our letter when read.
DEVELOPMENT OF THE CODES
From very early in 1940, the staff of MI9 were involved in devising codes. By April of that year, Lieutenant Commander Rhodes and Flight Lieutenant Evans were spending a great deal of their time in trying to perfect a suitable code. Initially known as the HK code, it had been suggested by Mr Hooker in the Foreign Office and was regarded by MI9 as the best idea put forward for a straightforward and simple code. The code was taught to the selected RAF and Army personnel. It was imperative that a detailed record of those briefed in the code was kept and that their families were also subsequently briefed, should their sons be unfortunate enough to be captured: as with all MI9’s records, these were held on a detailed card index.
The system of codes steadily developed and related research work is regularly mentioned in the War Diary, although no detail about the construction of the codes and methods of encryption and deciphering was ever disclosed in the monthly reports. That detail was, however, included in other reports produced at the time and it is clear that work continued throughout the war on the development of the codes. There were eleven codes developed in all, some being retained for very specific use. Codes I, II, III and VI were apparently developed for use in general correspondence with the camps. Code III was developed during early 1942 and was in use in some of the camps later that year. Although regarded as an effective code, it apparently limited the length of the message when compared with Code II and the code users appeared to be more prone to making errors in their messages. While it had proved relatively easy to spot errors with Code II, it proved to be far more difficult to spot errors with Code III. By April 1942, the development of Code VI had progressed and was being taught to potential code users. Code V was specifically developed for use in Oflag IVC (Colditz). This code was established within the camp by communicating its detail through code users there who were already using Code II. The first message using the new code was received from Colditz in October 1942: it had been correctly encoded in every respect. Code IV was given to the Americans’ MIS-X for their use. After the USA entered the war, MI9 had advised particular code users to brief selected US prisoners of war in the oflags, in anticipation of them being ultimately segregated. Code VII was used in the Middle East and Code VIII was retained for special operations, in particular those being organized by the Special Operations Executive (SOE). Codes IX, X and XI were apparently developed but had never been used by the time the war ended.
THE CODED LETTER WRITERS AND THEIR ROLE
Coded messages contained three different and important types of information: intelligence, the state of morale in the camps and planned escapes. The extent of the role played by the coded letters in terms of the intelligence which was actively sought and supplied is, perhaps, one of the more surprising aspects to emerge in the course of this study and one which appears previously to have been largely unacknowledged by historians. Certainly Julius Green’s book, From Colditz in Code, revealed the extent of his own involvement in responding to MI9’s requests for current intelligence information. By 1941 Green was in the Marlag and Milag Nord camp at Sandbostel, close to Bremen, and coincidentally the camp in which John Pryor was held at the same time.
The Marlag and Milag Nord camp at Sandbostel in 1941.
Green received a letter dated 11 February 1943, purporting to be from Philippa, possibly his sister, and ostensibly chatting about the mundane matters of the family’s general health, especially that of ‘Aunt Eleanor’ and ‘Daddy’. He was asked in the coded request:
WE KNOW OF TWO LARGE OIL PLANTS WHICH WE CALL BLECHAMMER NORTH AND SOUTH ARE EITHER OR BOTH PARTLY WORKING OR COMPLETED. IS THERE A THIRD PLANT MAKING AVIATION PETROL NEAR HEYDERBRECK
Green replied on 24 March 1943 in a letter to his ‘Dear Dad’ which appeared to talk about war bonds and investments and which he signed ‘Your affec. son Julie’, his familial nickname. However, Green had managed to encrypt within his letter the response:
BLECHAMMERS MAKING FROM 6 TO 9 THOUSAND QTS OIL DAILY I’VE ACCESS TO PLANT
As a dentist, Green was in the privileged position under the Geneva Convention of being allowed rather more freedom of movement than most prisoners of war, being a ‘protected person’ and regarded as a ‘non-combatant’. Doctors and padres also belonged to this group and it is known that MI9 maximized the opportunities presented. In Green’s case he felt on occasion overwhelmed by the amount of potentially valuable information he was able to acquire, commenting ‘so much information was pouring in to me now that I could not possibly encode it all’. Part of what he saw was evidence of the extermination programme of his fellow Jews which he described in his book in hauntingly moving terms:
Once, on the way to visit the main camp at Lamsdorf, my guard and I had to change trains. In a siding we saw a train of closed trucks from which an intolerable stench issued . . . we walked back with the moaning and whimpering from the trucks in our ears . . . The trucks contained Hungarian Jews who were being transferred to an extermination camp for ‘processing’. The sound has never left me and I still hear it.
It is not known whether Green ever reported this experience to MI9 or whether any action about the concentration camps was ever taken prior to liberation but it is clear that their existence was known to some of the prisoners of war.
John Pryor in 1951.
Similarly, John Pryor, a captured naval lieutenant, was also providing intelligence which would clearly be of considerable assistance to the RAF for targeting purposes. In a letter he sent to his parents in December 1942, which at face value was describing the gardening activities in the camp and the Christmas parcels which had been received from the Red Cross, he encrypted a message which provided precise locational details about large ammunition dumps. The letter is shown later in this chapter while its detailed decoding is fully explained in Appendix 10.
Since all Pryor’s received correspondence was lost during his repatriation in 1945, there was initially no indication that he was responding to a received request or simply providing acquired intelligence. However, it subsequently emerged that he was, in effect (just like Julius Green), responding to requests for information, as copies of some coded letters to the camps were kept by MI9.
MI9 also used coded letters to assess the morale of prisoners of war in the many camps with which they were able to establish and maintain contact. In March 1941 Pryor had written a letter to his parents mentioning the vegetable garden, receipt of parcels and a letter from home. In it he had managed to encrypt the coded message:
OWING SUPPOSED CONDITION PRISONERS CANADA WE MAY SUFFER HERE URGENT INQUIRIES NECESSARY
These words conveyed information that there were fears amongst the prisoners who apparently expected the German guards would take retaliatory action over the reported mistreatment of German prisoners of war being held in Canada.
Prisoners at Stalag Luft III (Sagan) tending their garden. John Pryor frequently wrote about the challenges of maintaining the garden in the sandy conditions of Marlag and Milag Nord camp.
DECODING REQUESTS FOR ESCAPE AIDS
The principal interest of the coded traffic, however, in so far as this study is concerned, is to demonstrate the importance of contact in requesting and providing the wherewithal to assist planned escapes. In a letter sent in May 1942 to his parents, which at face value purported to talk about the books he wanted and the extent to which the camp gardens were improving, Pryor managed to encrypt the following message:
CLOTHING AND LOCAL MAPS OBTAINED REQUIRE SOME OF BORDERS ESPECIALLY SWISS PASPORT INFORMATION AND RENTEN MARKS
Despite the spelling mistake in ‘passport’, it was unmistakeably a request for a
ssistance to support an escape. Since this letter was the first to be decoded in this study, it provides an ideal example of the methodology employed to uncover the hidden message, shown later in this chapter. There is no indication as to whether he received a response to his request for maps of the Swiss border; however, it is more than likely that he did, since the Swiss border was certainly an escape route recommended by MI9.
An MI9 drawing of a chess set and its secret compartments, similar to the set that John Pryor described.
However, it is known from Pryor’s own memoirs written in his later life that he did receive early in 1943 a coded message in a letter from his (unknown) Auntie Florrie alerting him to expect a parcel from the ‘London Victuallers’ Company’ (almost certainly the Licensed Victuallers’ Sports Association, a known cover organization for MI9). He recounted how he was then detailed by the Escape Committee to be present in the Post Room to ensure that the parcel was not opened by the German censors, but was appropriated by the prisoners of war and carefully whisked away to be hidden until it could be opened and explored in more secure surroundings. He continued by describing the chess set he found inside the parcel and the subsequent splitting open of the chessboard to reveal its hidden contents, namely German currency, hacksaw blades, copies of a German Ausweis (work and travel pass or permit) and examples of letters of introduction. The items were handed over to the Escape Committee. Interestingly, when it came to Pryor’s own escape (described in detail in Chapter 7), the route he attempted was not across the Swiss border but via the Baltic ports which were located geographically very much closer to the Marlag and Milag Nord camp.
There is also evidence contained in a letter sent in June 1943 to Lieutenant F. C. Hamel of the Royal Naval Volunteer Reserve (RNVR), also a prisoner in the Marlag and Milag Nord camp, purporting to be from his mother. It carried, however, a hidden message from MI9 which read;
DECCA RECORDS ALGER SOAK COVERS TO GET MAPS
It appeared to alert him to the despatch of a parcel to an individual named Alger. The message also shows that MI9 was continuing to use gramophone records but, instead of hiding the maps in a laminated compartment in the centre of the record, they were rather encapsulating them in the record covers, probably in similar fashion to the method used to hide them inside playing cards.
VOLUME AND PASSAGE OF CODED LETTER TRAFFIC
MI9 responded promptly to requests for information and equipment to aid escape, such as currency, passes, maps, saws and compasses. They could advise on routes, specifically which were the best and most likely to result in a successful escape and which to avoid. By 28 February 1941 most of the coded letters received in London contained requests for escape materials and German currency. By this time, MI9 had developed Code II and were also briefing men involved in particular covert operations. One disadvantage of the coded letter was the length of time it could take to reach its destination in either direction. It often took weeks and sometimes months for the letters to arrive. It appears that MI9 enjoyed more success in maintaining contact with the camps in Germany than with those in Italy. The relative lack of success in Italy was ascribed to the inefficiency of the Italians as ‘mail and parcels could take over a year and were often lost or destroyed’. The transit and delivery of letters and parcels to the camps in Germany appeared to be rather more swift and efficient. It is an irony that Teutonic efficiency apparently contributed to the success of the escape and evasion programme.
English and French prisoners of war receiving mail at a prison camp in the Castle of Wülzburg, Bavaria.
The numbers of letters steadily increased as more personnel were briefed in their use and as more men were captured. In the month of March 1941, sixty coded letters were received in MI9 and fifty-six were despatched. Four months later the total number of acknowledgement slips for parcels and coded letters received from the camps had increased to 4,279 or approximately 138 every day. Incoming letters were picked up by the Censors who were given a list, known as the Special Watch List, by MI9 of the names to look for and ensure that any letters from them were redirected to MI9. By December 1941, there were 928 names on the list and MI9 knew it could potentially rise very quickly to 1,500. They recognized how challenging and taxing it was for the Censors to pick up all the coded letters. This identification of which letters to decode was, after all ‘the vital link in the chain and, if broken, the whole structure will collapse’. MI9, therefore, made every effort to ensure that the list of names was kept as current as was humanly possible in order to make the Censors’ job less onerous. The decoding work was regarded as urgent and always treated as a priority by MI9. Once they had decoded the hidden messages, the letters were passed on to the families.
Matters relating to escapes were dealt with by MI9; anything relating to technical or operational intelligence was passed immediately to the appropriate departments of the three Services. It was not unknown at this stage of the war for over a dozen intelligence reports to be received in a month. They were also succeeding in speeding up the transit of coded letters so that, by the end of June 1941, the War Diary entry notes an example of a letter that was despatched by MI9 on 10 May reached the particular camp during the first week in June and a reply was received in MI9 on 29 June. By this time there were seventy-two coded correspondents operating in the camps in Germany and Italy.
Prisoners of war who were being transferred to different camps would often pass on their code to a fellow prisoner to ensure that contact with the camp was not lost. It was also the case that some prisoners who were to be moved were briefed by code holders so that the code could operate from the camp into which they were being moved. Such was the case with John Pryor who indicated in his memoirs that it was during January 1941 while he was in Oflag VIIC/Z at Titmoning that he was approached by a junior Army officer who had heard that the naval prisoners were to be moved to another camp. He asked Pryor if he would be prepared to learn a secret code so that messages could be hidden in his normal letters home. Pryor confessed that he was initially suspicious, thinking that the officer might be a German plant. He approached the Senior British Officer, General Fortune, and was reassured that the approach was genuine. Pryor proceeded to learn the code.
This practice of teaching the code methodology to others indicates the close cooperation which existed between the prisoners of different Services and was a practice which Pryor himself used later on in his captivity. In March 1942 he wrote a letter in which he hid a message indicating that he had taught codes to four others, namely:
ELDER 6 5 M HEAP 5 7 K HAMEL 7 5 O WELLS 5 6 J
There is an indication in his letter that he had been asked to do this since the hidden message starts by indicating that he had understood the coded letters dated 24 December and 3 January which he had received. Interestingly, but inexplicably, he found it necessary to resend the four codes he had allocated by repeating the message in a letter he sent two weeks later in early April. Not surprisingly, the two letters are superficially about quite different topics and the hidden messages, as a result, are encoded differently though relaying the identical information: in itself, this demonstrates the sheer versatility of the coded letter system.
It is clear from Pryor’s memoirs just how much effort went into the planning and execution of escapes. He was able to use the MI9 code and encrypt messages in some twenty-one letters to his parents which contained both intelligence and requests for assistance. His efforts serve as a stark reminder of the raison d’être of MI9 and the extent to which prisoners of war had taken on board the escape philosophy. Of necessity the codes were hardly simple; they had to avoid detection by the German censors. To encode letters, as Pryor did, must have taken many hours of intellectual effort in circumstances which were hardly conducive to such activity. It is to his eternal credit, and that of the many other prisoners of war, that they continued to do exactly what MI9 asked them to do, harass the Germans at every opportunity, attempt to escape, be the proverbial thorn in the enemy’s side, an
d provide intelligence in response to requests. In return, MI9 stuck determinedly to their part of the ‘agreement’, providing all the escape aids in their considerable armoury to aid the planned escapes. They also ensured that all families who had sons in captivity and who had been schooled in the art of sending and receiving coded letters knew exactly what was happening.
By July 1941, MI9 was operating a network of 254 code correspondents, which rose to 928 by December. By February 1942 they were in contact with twenty-seven camps in Germany and Italy and estimated that the system allowed them to maintain contact with over 62,000 prisoners of war. They also knew of 465 attempted escapes by that time.
