In this correspondence, William Friedman questioned AGD’s memory over the Zimmermann Telegram and how it was transmitted.
On 4 May 1958 AGD claimed that ‘there were 4 (not 3) ways of transmission &, as you say, 2 bases’.1 Friedman wrote on 26 May, still uncertain about how many routes were used:
I note that you feel sure that there were four and not three ways of transmission. This would make it appear that our deduction with regards to the non-use of the Nauen-Sayville route is incorrect. Unless, of course, there is one additional route which we don’t mention.2
In June, Currier was able to give AGD a copy of the telegram as well as a new book dealing exclusively with it by Barbara Tuchman. Both AGD and Friedman subsequently questioned claims made in the book that code No. 13040 was found by Hall amongst papers belonging to Wilhelm Wassmuss, German Vice-Consul at Bushire on the Persian Gulf. As well as the James and Tuchman books, a BBC radio broadcast on 26 May talked about the Zimmermann telegram and gave a ‘very full & accurate details of 40 OB & the methods employed and even the names of the actual performers’. AGD assumed that James has advised on the programme, and both wondered how James had gotten clearance for his book. In July, Friedman and his wife attended a summer symposium for a specially-selected group of mathematicians, including two from GCHQ, and he has given talks on the telegram and other ‘certain classified matters’. In a lecture on 27 June 1958, Friedman had read from one of his letters from AGD.3
On 23 August, AGD sent his recollections about Room 40 to Friedman:
But do remember also the origins of ‘40 OB’ – a collection of amateurs with a good knowledge of German and no experience of cyphers collected by Sir A. Ewing in Aug 1914 to study the vast amount of W/T material which was coming into the Admiralty. Within a few weeks, NAVAL material was sorted out & the First Lord (Churchill) instructed us to make a profound study of the methods of the German Admiralty. We carried this out successfully & the staff grew & by the middle of 1915 we began to seek fresh fields where we could tackle the Germans. But we all had to learn the technical side of our job! Not easy work even for enthusiastic amateurs. Out of that small body & a similar party in the W.O. studying the German Army, & you know as well or better than I what has grown up from these sections!4
On 30 August, Friedman wrote to AGD and queried his assertion that the Zimmermann Telegram had been sent via the ‘main line’ Nauen-Sayville route. AGD replied on 5 September:
I know that we received the Z.T. by 4 routes, one by W/T Nauen-Sayville & three by cable of which one was procured by M. W/T interception was then in infancy & results often garbled. Cables were only available to us after delays as they were controlled by censors & not directly by us. I only remember that we did receive a lot of W/T traffic on this ‘main line’ route but I cannot confirm that we did hear the Z telegram accurately on this route.5
Friedman replied on 19 September:
You make a categorical statement that the ‘main line’, the Nauen-Sayville route was used. Permit me to say, for your information, that I am troubled by your statement, because in a good deal of research I find no evidence that this route was used. Whenever that radio channel was employed, the messages were carefully examined and decoded by means of a copy of the ‘Englischer Chiffre’ which was deposited with the State Department by Ambassador Bernstorff. I do not see how a message such as the Zimmermann Telegram would have escaped the censorship which was imposed on the radio route. I know, of course, that a radio route from Nauen to Mexico City was being established but there was so much difficulty in communication via that channel that it was not until months or perhaps years after the Zimmermann Telegram episode that it could be used in a practical manner. Of course, it is possible that Nauen may have transmitted the message in 13040 via that channel to Mexico City and this was what was intercepted in London. Do you remember anything to this effect? Could this serve as an explanation of your recollection that the radio route was used? Do you recall whether German Government official messages, transmitted via the ‘main line’, were at any time disguised by ‘phoney’ addresses and signatures intended to make it appear that they were strictly business messages between business men in Germany and in the United States.
I know that three other (cable) routes were used but it is important for my official story about the Zimmermann Telegram (a revision of the brochure you had and which you returned) to be accurate with regard to whether or not the radio route was actually used.6
AGD replied on 5 November:
As to the routing of the telegram, I said in the final paragraph of my long note of recollections that you were in a position to disprove any of my views if you have access to the records either in the State Department or in the Cable & Wireless companies though I greatly doubt if Sayville has preserved copies of all the traffic they received from Nauen. But I am surprised that you consider that all traffic on this route was in the Englisher Chiffre. You say that traffic between Bernstorff & Berlin was in 7500 & you thought that possibly Z Tel. was so sent. Now I make another suggestion which I will develop if you wish – if the German F.O. had the ‘nerve’ to use the good-will of your Ambassador in Berlin to send dispatches by his bag why should they hesitate to include ‘unreadable’ cyphers amid the telegrams or radiograms sent in the Englisher Chiffre. Again my memory fails me but I think they did.7
Friedman sent his final letter on the subject to AGD on 29 December:
About the Zimmermann Telegram and whether it was sent by radio in addition to having been sent by cable over more than one route: I now have a Photostat of the records of that episode as they appear in documents of the German Foreign Office. A soon as I get an opportunity I’m going to read a long memorandum in those records, dealing specifically with how the telegram was sent, speculations as to how the plain text fell into American or British hands, and so on.
In answer to AGD’s ‘other suggestion’, Friedman goes on to say:
The answer to your question is that every message sent via the radio route Nauen-Sayville or Nauen-Tuckerton was carefully scrutinized by our communications censorship imposed long before the date the Zimmermann telegram was sent. No, I’m pretty sure the telegram couldn’t have gotten through that way. I think I know how the theory that the telegram was sent by radio came to be held but it would take too long to explain it in a letter. When and if we come to England next autumn I’ll hope to visit you again and tell you.8