Spain was another country known to be sympathetic to Germany. Following the example of the Sayonara escapade, Hall sent another luxury yacht, the Vergemere, on a cruise down the Spanish coast to discover if Spaniards were doing anything to help the German war effort, for example by preparing to refuel U-boats before their long missions out into the Atlantic. This time he decided not to use a fake American as skipper, but to select a sports-loving British peer who must appear to be so wealthy that, despite the war, he was still bent on taking a pleasure cruise down the Mediterranean. The person he found to play the part of the stage aristocrat was Sir Hercules Langrishe, a charismatic Irish baronet and keen sportsman. Langrishe cruised from port to port, inviting influential Spaniards on board the Vergemere for lavish champagne parties, all sponsored by Hall. He seems to have picked up enough intelligence for Hall to realise that Spain needed to be continually watched. As an unexpected by-product of the operation, Langrishe convinced many Spaniards that reports that the British were suffering great privations at home could not be true. The Germans apparently mounted a similar exercise at the same time, taking a steamer along the Spanish coast to sound out local opinion. But, unlike Langrishe’s extravagant champagne parties, the Germans on their boat served nothing more exciting than a glass or two of beer. Not surprisingly, the Spaniards much preferred British to German hospitality.
Hall had proved to be a ruthless and determined intelligence chief, willing to do anything to attain his ends. Hall and his Scotland Yard colleague Thomson made a formidable double-act. Thomson invited Hall to be present when he was interviewing several suspects and realised that Hall was extremely able at getting people to talk. But sometimes it is difficult to separate fact from fiction in the stories that grew up around Hall. At one point, he is supposed to have interviewed a naval figure who had been brought in from a steamer off Ireland. The man was thought to be a German but denied this, claiming to be an American who had never set foot in Germany in his life. Hall listened to what the man had to say and was apparently sympathetic to the suspect when he suddenly barked out in German the order for ‘Attention’. The man automatically leapt upright before realising the game was up and admitting his true German identity.
On another occasion, Hall and Thomson together interviewed Margaretha Zelle, better known by her nickname of Mata Hari. Famous in Europe as an oriental exotic dancer, Zelle was Dutch and had learned to dance in a supposedly native Hindu style in the Dutch East Indies. Before the war she had become famous in Paris for her erotic dancing and for posing for nude photographs, clad only in a few discreetly placed jewels. She conducted well-known affairs with various senior French officers and officials. After the outbreak of war she carried on this lifestyle and was suspected of passing on to the Germans information she gathered by seducing French officers.
She regularly travelled between Paris and Holland by boat from Spain, and when she landed at Falmouth on one of these journeys she was arrested and taken to London for interrogation. Hall and Thomson were convinced she was spying for the Germans and was carrying information which she had committed to memory. But there was insufficient evidence to charge her and she was allowed to continue on her journey. It was said later that Hall and Thomson had freed her because in Britain there was no death penalty for female spies at the time, but had passed on details to the French who arrested her on arrival. In fact this was not the case; Zelle continued spying for the Germans for another year before she was arrested, found guilty and condemned to death in France. She was executed by firing squad in October 1917.
Hall’s powers of persuasion became equally legendary. Early in the war, he had become aware that the Home Office was not censoring the overseas post effectively and suspicions reached him that enemy agents were simply sending their reports back via contacts in neutral countries through the regular post. When Hall sent in his own Admiralty team to the post office at Mount Pleasant in London where overseas mail was handled, they soon found detailed information as to how Germany was buying goods from neutral countries to beat the blockade imposed by Britain. This invaluable evidence helped the navy to tighten the blockade on Germany.
However, when Hall’s unofficial censorship activities became known he was summoned to see the Home Secretary, Reginald McKenna. Hall arrived to find McKenna looking very stern, standing in his office by the fire, resting against the mantelpiece with his hands on his lapels. He said it had been brought to his attention that without his authority Hall had been ‘tampering with the King’s Mail’, and threatened him with a two-year prison sentence for committing such a heinous crime. Hall later wrote that he felt like a naughty schoolboy being called in to see the headmaster for misbehaving. When, however, he asked permission to speak and explained to the Home Secretary what he had been doing, why he had been doing it and what he had found as a consequence, the mood changed completely. McKenna became fascinated by Hall’s work, and the two men sat on the settee and talked for some time. By the end of the meeting, the Home Secretary was suggesting the establishment of an entirely new organisation, the War Trade Intelligence Department, to monitor German trade in goods prohibited under the blockade. By the time Hall left the room, McKenna had become a great fan and told Hall that the Admiralty should continue censoring the post until the new organisation could be formed.8 The War Trade Intelligence Department was to do vital work in ensuring the effectiveness of the blockade. And Hall had talked his way out of one of the biggest crises of his intelligence career.
Hall was always keen to feed false information to the Germans, to deceive them into wasting precious time or resources on something completely useless, as he had done with the misinformation about an Allied invasion of Schleswig-Holstein. In the summer of 1915 he came up with the idea of planting on German intelligence a false code book; by sending messages using the code he could then feed misinformation into the German system. Hall and his colleagues spent some time planning how to get the book into German hands without giving the impression that it had been planted, and the scheme they came up with was worthy of any pre-war spy novel. There was a hotel in Rotterdam, in neutral Holland, where English businessmen used to stay. It was known that German agents operated there and that a certain ‘blond lady’ would always check in whenever any senior-looking British official arrived. It was also known that the hall porter was in the pay of the Germans. Hall persuaded Sir Guy Locock, who had been in the Diplomatic Service for twelve years, to agree to take the fake code book out to Rotterdam in a secret dispatch case with the apparent intention of passing it on to the British consul. Well versed in the ways of diplomats abroad and able, in Hall’s phrase, to ‘carry a despatch case in just the right way’, Locock was bound to attract the attention of the German agents at the hotel.
Locock checked in and, after unpacking in his room, went out for a walk. He found a spot among some barrels in the nearby harbour where he could hide but still see the window of his room. Having found this observation spot he returned to the hotel where he noticed a blond woman checking in, alone, to a room further along his corridor. As it was a weekend, Locock could not deliver his important cargo for a couple of days and had to wait in the hotel. After dinner, the hall porter got into conversation with him and suggested it must be very dull for the visitor being by himself in a strange city. Locock agreed. In a confidential manner, the porter told him of a very fine club in Rotterdam where any gentleman from the hotel would receive a warm welcome. Locock put on a show of great interest and within minutes had rushed out of the hotel in full view of the porter. However, instead of going to the club, Locock went to his observation point in the harbour, where in a few minutes he saw the light in his room go on and a shadow cross the blind. He imagined the blond woman looking through his things and finding that, in his apparent haste to depart to the club, he had not locked the despatch case that he had hidden below his clothes. Before long the light in his room went out. But of course no agent worth their salt would simply steal the code book. That would be a giv
eaway; when the diplomat returned and found the book missing, its use would be instantly cancelled and no advantage would be gained. So Locock had to wait in hiding while the blond woman and any accomplice photographed the entire book and then returned it to his room. Shortly after 1 a.m. he saw the light in his room go on again briefly. Locock waited another half hour and then returned to the hotel in a very merry state, ensuring he spoke with the hall porter – or at least tried to speak to him, as by this point the Englishman was slurring his words so badly that he appeared to be barely capable of speech. The hall porter would think he had spent a delightful few hours at the club.9
Hall knew that if the Germans were to accept the code book as genuine, he would have to send some fairly meaningless coded messages to which a British ship somewhere would have to respond. However, after all the cloak-and-dagger play acting it seems that no substantial pieces of misinformation were ever sent or, if they were, they remain secret. But there is a fitting postscript to the story. A year after the blond woman had photographed the original code book, Hall judged it was about the right time for an appendix to the code to be issued, and found another agent to take the new document out to Rotterdam. Instead of repeating the same ruse, this time the agent approached the Germans in the Dutch city and, with a story of disaffection and hatred of Britain, offered to sell them the appendix. The Germans paid £500 for the appendix, a very substantial sum. It is not recorded what happened to the money.
From the moment he took charge of naval intelligence, Hall had started to collect and sift information from every area where British forces were or might be engaged. By the summer of 1915 he had an efficient network in place in the eastern Mediterranean, a region that was to become of enormous interest to Britain. German and Turkish radio signals regarding troop movements were intercepted and sent back to Room 40 for decipherment. Looking further afield, Hall found evidence that the Germans were trying to foment trouble in India by encouraging a revolt against British rule. It seemed that a group of revolutionary Indians living in America had approached the German embassy in Washington and asked for sums of money and supplies; indeed the Germans eventually paid out a small fortune. By following the German diplomatic cables, Hall knew precisely what was going on and who was involved. Nothing ever came of German attempts to overthrow British rule in India. But because Germany’s undersea cables had been destroyed at the beginning of the war, and German diplomatic messages between Berlin and Washington were all sent by radio, Hall had the means to keep an eye on these communications that had the potential to stir up major trouble for Britain.
By the autumn of 1916, after the terrible loss of life suffered at both Verdun and on the Somme, and after the Battle of Jutland had shown they could not defeat the Royal Navy at sea, the German War Staff started to consider the possibility of unrestricted submarine warfare – that is, instructing its U-boats to sink on sight merchant ships of all nationalities. By October well over one hundred U-boats were ready to operate in the Atlantic. The Germans calculated that if they could sink about 600,000 tons of shipping per month, the Allies would be able to survive for only six months before Britain was brought to its knees and forced to seek a truce.
The sinking of American ships would risk causing outrage in the United States, of course, and the Germans had to consider the possibility that America would declare war on them as a result, but in Berlin it was decided that this was a risk worth taking. Stories of the USA’s total unpreparedness for war convinced the Germans that American troops would make no difference to the struggle on the Western Front in the six months before the Allies threw in the towel. Moreover, President Woodrow Wilson was so committed to a policy of peace that the Germans thought there was a strong possibility he would not declare war even if American ships were being sunk. So, on 9 January 1917, the Kaiser gave his permission to launch unrestricted submarine warfare from 1 February.
A week after the decision was taken, on the morning of Wednesday 17 January, at about 10.30 a.m., Hall was at work in his office on the usual round of papers when one of his leading code breakers asked to see him urgently. Nigel de Grey and the Rev. William Montgomery had partially deciphered a message that they could see was of immense importance. De Grey entered Hall’s office and asked his boss, ‘Do you want to bring America into the war?’ ‘Yes my boy,’ replied Hall. ‘Why?’
De Grey explained that they had just deciphered a ‘rather astonishing message’ from the German Foreign Office to their ambassador in Washington.10 In the first half of the message it was clear that Berlin was telling its ambassador that it proposed to begin unrestricted submarine warfare on 1 February. The second half was less complete but seemed to say that if this new strategy was likely to bring America into the war, then the Washington ambassador should contact the German ambassador in Mexico. There were additional words or phrases that did not make sense, like ‘Japan’, ‘inform the President’, ‘war with the USA’ and ‘our submarines’.11 The message, or telegram, came from none other than the German Foreign Secretary, Arthur Zimmermann.
Zimmermann’s telegram had in fact been sent via three separate routes. First, there was the radio transmission, sent from Nauen on long wave using a new code referred to in its header as 15042. This was a variation of the code the cryptanalysts in Room 40 already possessed, known as 13042, and the difference might explain why de Grey and Montgomery had not been able to decipher the full message. Second, Berlin had started to send its diplomatic messages to the Americas via a neutral country, Sweden. The Swedish Foreign Ministry would forward a German message in the diplomatic bag to their ambassador in Buenos Aires, who would then act as a sort of consular postman and send it on to the relevant German embassy, in this case the one in Washington. Third, and most remarkably, Berlin had also sent the message in code, tagged on to another cable to the US State Department as part of an agreement the Germans had made to send confidential messages to their ambassador in Washington. To discuss war with America on a cable sent through the US State Department was a scandalous abuse of a diplomatic privilege given to Germany and a remarkable affront to the USA, but the German Foreign Office was confident that its codes were so secure that no one would ever decipher such messages.
Over the next couple of weeks Room 40, who had been monitoring these diplomatic communication routes for some time, picked up all three versions of the telegram and deciphered the full message. It was clear that in addition to warning his man in Washington of the decision to resort to unrestricted submarine warfare, Zimmermann was cooking up a new and more devious plan. He hoped the Mexicans could help to bring Japan into the war on the German side. Furthermore, he was asking his Mexican ambassador to discuss with President Carranza of Mexico the possibility of a German alliance. Mexican-American relationships were not good and, most audaciously of all, Zimmermann was offering German support for a Mexican invasion of Texas, New Mexico and Arizona to recover lost territory should America enter the war. News of German intentions to aid an invasion of their own country would doubtless spark such fury in the United States that it might in itself provoke America into war.
Hall was hugely excited to receive the deciphered telegram and instantly recognised that it was political dynamite. But it presented him with a major problem. How could he use the information without giving away the fact that Room 40 was listening in to and reading German diplomatic codes? If Berlin thought there was any possibility that British Intelligence was deciphering their radio messages they would immediately change all their code books and it might take years before Room 40 could catch up again. Alternatively, using the version that had gone through the neutral countries, either Sweden or the United States, would reveal that Britain had been reading the diplomatic messages of friendly neutrals. This too would be seen as totally unacceptable behaviour. Although there was nothing Hall wanted more than for America to join the war on the Allied side, he was not willing to compromise Room 40 for that end. He faced the eternal problem confronting intelligence chiefs, ho
w to make use of the most secret information without revealing the source from which it had arrived.12
Hall decided the best thing to do for the moment was nothing at all. He instructed de Grey to destroy all versions of the decrypt except one, which was kept under lock and key in his office, and then he simply waited. Possibly the Germans’ use of open war at sea might force the Americans into the conflict and it would be unnecessary to do anything further. However, he knew that President Wilson had just won an election on the basis of keeping America out of the war. Although some within the United States, mostly on the eastern seaboard, were sympathetic to Britain and France, many other important groups – like the Irish and German communities -were hostile. And in the west of America, most people saw the European war as remote and irrelevant. It was not at all clear how the Americans would be likely to respond.
It seems remarkable now that Hall shared this extraordinary piece of intelligence neither with his masters at the Admiralty nor with the Foreign Office. Matters relating to the relations between foreign powers were obviously their principal concern. Something on this scale would probably have been referred up even to the Prime Minister. Hall had great respect for Sir Arthur Balfour, who had left the Admiralty to become Foreign Secretary. But he had sufficient self-confidence, or what might better be described as arrogance, to feel he should try to control this story himself.
Hall therefore sat back and followed decrypts of the exchanges between the Berlin Foreign Office and their ambassadors that Montgomery and de Grey passed on to him almost daily. He could read that Bernstorff in Washington was hostile to the concept of unrestrained submarine warfare and tried to persuade the diplomats in Berlin to reconsider their policy. They refused, a fact which Hall was no doubt relieved to read. The German ambassador in Mexico, Heinrich von Eckhardt, reported back that the Mexican president was friendly to Germany and in return for support would consider allowing Germany to use Mexican naval bases to refuel and service its U-boats. This threat promised an even greater escalation of the war.
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