by Alastair Denniston- Code-breaking From Room 40 to Berkeley Street
In July 1916, Hall received a telegram from Room 40 which provided an insight into Germany’s view of US/Mexican relations.
From: – Washington
To: – Berlin
July 25th, 1916
The Mexican question has again reached the stage of diplomatic negotiations and may for that reason be regarded as settled for the moment. It becomes clearer and clearer that the American Government has drawn back from a rupture because her military resources are not sufficient to face a war with Mexico. On every hand there was an absence of the first necessities of war. For that reason the decision of the Mexican question again rest with Carranza and Villa. If no new incident occurs, no breach will take place.
Wilson has no reason to be satisfied with the developments of the last few weeks. The pacifists praise him, but their friendship is ever with him. In all leading American circles Wilson is still blamed for his Mexican policy. To judge from certain American symptoms, it looks as if Wilson could not hope to be re-elected unless he succeeds in bringing about peace in Europe.
As regards our relations with the United States, the improvement which was begun makes slow but certain progress.
The English black list has evoked general resentment and will force Wilson to take steps directed against England.
Hall was concerned that Germany intended to deploy its submarines against merchant ships of all nationalities. If the US did eventually enter the war, it would be too late, as British and French supplies would be depleted. He wrote to Commodore Gaunt, Britain’s Naval Attaché in Washington, at the end of September 1916:
You will have seen by Lloyd George’s speech that for once in our lives we hold the same views. It has been a struggle to get our Ministers out in the open and say exactly what the people of England think. The Germans, I think, will start their submarine warfare within the next few weeks. They have tried for their armistice with neutrals and failed. I think they are now trying to secure an armistice direct and will fail again, and, when convinced that we mean war, they will go all out.
By October, 200 submarines were ready, having been refitted and their crews trained. Hall hoped that US patience would be exhausted but President Wilson had no intention of going to war unless all States supported it. In England there was a shortage of men and food and the Government, along with the Admiralty was under fire. At the end of November, Sir John Jellicoe handed over command of the Grand Fleet to Sir David Beatty and replaced Sir Henry Jackson as First Sea Lord. Less than a week later, Asquith resigned as Prime Minister and was replaced by Lloyd George, with Sir Edward Carson appointed First Lord and his predecessor Arthur Balfour as Foreign Secretary.
At the end of December, Room 40 decrypted a ‘code letter’ from Heinrich von Eckardt, the German ambassador to Mexico, to Chancellor Dr Theobold von Bethmann-Hollweg.
8th March
The Swedish Chargé d’Affaires, here, Herr F. Cronholm has, since he has been here, made no concealment of his sympathy for Germany and placed himself in close connection with this Legation. Since the closing of the Brazilian and Guatemalan Legations in August last year he is the only neutral diplomat through whom information from the enemy camp can be obtained. Further, he arranges the conditions for the official telegraphic traffic from your Excellency. In this connection he is obliged every time, often late at night, personally to go to the telegraph office to hand in his dispatches … Herr Cronholm has not got a Swedish order but only a Chilean one. I beg to submit to your Excellency, if your Excellency approves, that Herr Cronholm should be recommended in the proper quarter for the Kronenorden of the 2nd class.
In order to raise no suspicion on the side of our opponents, it would be more advisable to treat the decoration if it be granted, as a secret matter till the end of the war, and only to inform the recipient and his Government of it, and then only under the seal of promise not to publish his investiture until after the end of the war.
This proved that in certain quarters diplomatic privileges were being misused and the mail on all neutral ships should be examined. In particular, Swedish Foreign Office cipher telegrams needed to be brought to the Admiralty, as the Eckardt letter implicated the Swedish Chargé d’Affaires in Mexico, F. Cronholm, in handling illicit traffic. Examination of the Swedish cables revealed German code groups following a few Swedish groups in the messages. By January 1917, the Swedish Foreign Office had become, in effect, an integral part of the German diplomatic organisation. This was further confirmation of what Room 40 had discovered in September 1916, the two routes which Count Johann von Bernstorff, the German ambassador in the United States was using to communicate with his Government while bypassing British censorship. Room 40 was soon providing most of Bernstorff’s dispatches and the replies of his government. On 1 September 1916, Eckardt telegraphed Berlin: ‘The Swedish representative fears English suspicion and complains in Stockholm on account of his frequent telegrams. He suggested that for the future his reports about ships might be allowed to lapse.’
In an October dispatch, Eckardt was asking why he had not had a reply about Cronholm’s decoration and reported on the attitude of President of Mexico General Venustiano Carranza: ‘Carranza, who is now openly friendly to Germany, is willing to support, if necessary, German submarines in Mexican waters to the best of his ability’. An even more important dispatch, sent on 12 November, said that:
The Imperial Government proposes to employ the most efficacious means to annihilate its principal enemy, and since it designs to carry its operations to America with the object of destroying its enemy’s commerce, it will be very valuable to have certain bases to assist the work of the submarines both in South America and in Mexico, as for example, in the State of Tamaulipas. Accordingly, the Imperial Government would see with the greatest pleasure the Mexican Government’s consent to cede the necessary permission for the establishment of a base in its territory, on the understanding that any arrangements completed will not involve the slightest damage to the dignity or integrity of Mexico, since that country will be treated like the free and independent nation which it is. The Imperial Government being perfectly acquainted with the special circumstances through which Mexico is passing at the current time – in that period of reconstruction in which being a young nation she finds herself – would like to know what advantages Mexico would find suitable on her part, especially in the financial and economic crisis through which she is passing, if she agrees to the desires of the Imperial Government
On 16 January 1917, an encrypted telegram was sent by Arthur Zimmermann, the German Minister of Foreign Affairs in Berlin, to Ambassador von Bernstorff in Washington. It was to be forwarded on to Eckardt in Mexico. The telegram would forever be known as the Zimmermann Telegram.65 The following day, Room 40 received from Cable Censorship two copies of the telegram and by the end of the day had partly decrypted it. It would prove to be one of the most significant Sigint events in the twentieth century and Room 40’s greatest success.
One had been sent to Washington through American diplomatic channels. It was in a new two-part code known as Code 750066 which had been recently introduced and which Room 40 had not broken.67 The second had been sent via the Swedish Minister in Berlin to Stockholm, Sweden. From there it had gone via cable to Buenos Aires, Argentina, and from there via cable to Washington and then on to Mexico City. The telegram had been encoded using an old German one-part code, known as Code 13040.68 Most but not all of this code had been recovered by Room 40.69 This method became known as the ‘Swedish roundabout’.
During the morning of the 17th, Knox and De Grey recovered a ‘skeleton version’ of the text. In the event of war with the US resulting from the unrestricted submarine warfare which Germany would be beginning on 1 February, Eckardt was instructed to invite Mexico to join in the conflict. In turn it would receive the territories of Arizona, New Mexico and Texas. De Grey knew that this proposal could change US policy with regards to the German threat and overcome President Wilson’s reluctance to go to war
. He showed it to Hall, by-passing Ewing who was still nominally in charge of Room 40. De Grey later wrote that, ‘Blinker Hall was always accessible to the lads of Room 40, at least he was to me at the time, because I was getting him all the news from diplomatic Germany and Hall had made a compact with a few of the research party that if ever we dug out anything of real importance we were to take it to him without showing it to Ewing, whom he mistrusted as a chatterbox (and rightly).’70
De Grey showed Hall the partially-deciphered message on 17 January and it read:
Berlin to Washington
W.158. 16 January 1917.
Most Secret for Your Excellency’s personal information and to be handed on to the Imperial Minister in (?) Mexico with … by a safe route.
We propose to begin on 1 February unrestricted submarine warfare. In doing so, however, we shall endeavour to keep America neutral … (?) If we should not (succeed in doing so) we propose to (?Mexico) an alliance upon the following basis:
(joint) conduct of war
(joint) conclusion of peace …
Your excellency should for the present inform the President [of Mexico] secretly (that we expect) war with the USA (possibly) (… Japan) and at the same time to negotiate between us and Japan …(Indecipherable sentence meaning Please tell the President) that … our submarines … will compel England to peace within a few months. Acknowledge Receipt.
Zimmermann
Hall would later give his own account of first seeing it:
I am not likely to forget that Wednesday morning, 17 January 1917. There was the usual docket of papers to be gone through on my arrival at the office, and Claud Serocold and I were still at work on them when at about half past ten de Grey came in. He seemed excited, ‘DID,’ he began, ‘do you want to bring America into the war?’ ‘Yes, my boy,’ I answered, ‘Why?’ ‘I’ve got something here which – well, it is a rather astonishing message which might do the trick if we could use it. It isn’t very clear, I’m afraid, but I’m sure I’ve got most of the important points right. It’s from the German Foreign Office to Bernstorff.’71
In 1918, Hall testifying before a Commission investigating an explosion in New Jersey, claimed that: ‘The German cipher book covering this system [Code 13040] of enciphering is in our possession, it having been captured by the British authorities in the baggage of a German consul named Wasmuss who was stationed at Shiraz while Wasmuss was engaged in an endeavour to cut a British oil pipe.’
Hall’s account is now considered to be at best a case of faulty memory. British intelligence may well have recovered copies of telegrams with the code text along with the corresponding plain text. This would have been of great assistance to Room 40 in reconstructing the 13040 code book. However, the more likely explanation is that Hall instinctively knew that it was better for the Germans to believe that 13040 had been captured rather than reconstructed by Room 40 cryptanalysis.
Hall had a number of problems to solve: should he make use of the telegram; if its disclosure was essential, he needed a complete and accurate text; and he needed to protect its source, Room 40; he needed to find a way to present the information to the President so that he and the American public were convinced by its authenticity; what should they do if Zimmermann denounced the telegram as a forgery? As De Grey recalled:
He asked for the best version that we could produce – in fact, we had got only a little further with the help of Rotter. He then discussed with me again the pros and cons. Obviously we had two fears. The first and by far the greatest was that we should ‘blow’ Room 40 – a crazy risk to run when it is remembered that we read the German naval codes operationally and always currently. Secondly we did not want to risk the fact that we took drop copies in London off the cables or reveal that we had bowled out the Swedes in a non-neutral act. The first would have lost us an invaluable source of intelligence if the coup with America failed, the second would have created an unpleasant situation at a pretty critical moment of the war. I remember him saying to me ‘Our first job would be to convince the Americans that it’s true – how can we do that? Who would believe? Is there any Englishman, whom they will believe? I’ve been thinking and the only person I think they would believe is Balfour. To all Englishman at that time Balfour stood head and shoulders above the politicians as the wise man, the elder statesman. Indeed I have always thought that Blinker’s use of Balfour as his mouthpiece was a stroke of genius (such as he used to exhibit from time to time).
Hall’s first problem was solved by 10 February when he had an almost perfect transcript of the Zimmermann telegram. It had been translated into English as follows:
Washington to Mexico
19 January 1917
We intend to begin on 1 February unrestricted submarine warfare. We shall endeavour in spite of this to keep the USA neutral. In the event of this not succeeding we make Mexico a proposal of alliance on the following basis: make war together, make peace together.
Generous financial support and an undertaking on our part that Mexico is to reconquer the lost territory in Texas, New Mexico and Arizona. The settlement in detail is left to you.
You will inform the President of the above most secretly as soon as the outbreak of war with the USA is certain, and add the suggestion that he should on his own initiative invite Japan to immediate adherence and at the same time mediate between Japan and ourselves. Please call the President’s attention to the fact that the ruthless employment of our submarines now offers the prospect of compelling England in a few months to make peace.
ZIMMERMANN
Hall ordered that all copies except the original and one decrypted copy be destroyed, given its obvious importance. He was not convinced that Germany’s intention to begin unrestricted submarine warfare on 1 February would persuade President Wilson to declare war. Publication of the telegram in the US would force his hand but this could compromise the work of Room 40. He was even reluctant to pass it to the Foreign Office for security reasons. However, if he could acquire a copy, he could claim that it was one of the messages passing from Washington to Mexico and that it had been decrypted by the American Intelligence Service. Hall showed the telegram to Lord Hardinge, the Permanent Secretary at the Foreign Office on 5 February and explained that the dispatch had not been in Europe and at worst, he could disclose its origins in secret to the American Government. At the same time, Hall secured from his agent in Mexico, copies of all telegrams sent by Bernstorff to Eckardt since 18 January.
On 8 February, Room 40 decrypted a second telegram from Zimmermann to Mexico:
Most Secret. Decypher personally.
Provided there is no danger of secret being betrayed to USA, you are desired without further delay to broach the question of an Alliance to the President. The definite conclusion of an alliance, however, is dependent on the outbreak of war between Germany and the USA. The President might even now, on his own account, sound Japan.
If the President declines from fear of subsequent revenge you are empowered to offer him a definite alliance after conclusion of peace provided Mexico succeeds in drawing Japan into the alliance.
ZIMMERMANN
Hall decided that the best solution was for President Wilson to release the telegram and say that it had been obtained and decrypted on American soil by Americans.
Hall consulted Balfour, the Foreign Secretary, who knew of Room 40’s activities, having been First Lord of the Admiralty from 1915 to 1916. He knew that Zimmermann had asked Bernstorff in Washington to send on to Mexico the text he had received, and that this would probably be in the same one-part code used for the direct transmission by the Swedes. This was likely, as it was the only code held by the mission in Mexico. Hall telegraphed the Naval Attaché in New York on 5 February, asking him to get hold of all telegrams sent to the German Embassy in Mexico since 18 January. On 10 February, he received a copy of just what he needed, the version of the telegram sent on from Washington to Mexico, in the one-part code that Room 40 could read. This was said to h
ave been acquired somehow from the Mexican telegraph office by the British Mission and could prove the telegram was authentic without compromising Hall’s true sources.
Hall needed to approach the Americans while at the same time, protecting his source, Room 40. He elected to speak to Edward Bell at the American Embassy. Bell had been posted to the US Embassy in London as Second Secretary on 1 September 1913, and had quickly established good relations with Hall and his staff, particularly Herschell and Serocold. He had the confidence of the US ambassador to Britain, Walter Hines Page72, who had taken up his post in 1913 and was much more pro-British than President Wilson. Bell provided a trusted link between the US and British Intelligence. Hall preferred to deal with Bell, as the US was neutral so their Naval Attaché, Captain Powers Symington, and his five assistants could not be given detail of British intelligence activities. Germany was active in the US through the activities of Ambassador Bernstorff, which included subsidising anti-British German-American and Irish-American organisations, stirring up trouble in India by funding Indian nationalists, organising the cutting of the Canadian Pacific Railway, sabotaging American factories working for the Allies and planting bombs on British merchant ships sailing from US ports. The American security services were not equipped to deal with these problems. Apart from Bell, Hall liaised with the British Ambassador in Washington, Sir Cecil Spring-Rice and made use of one of the British Naval Attachés in Washington, Captain Guy Gaunt. He kept Gaunt and his colleagues well informed, and wrote to them personally. He also liaised with Mr (later Sir) William Wiseman, a British businessman and Wall Street banker who became head of the British Secret Service in the US.73