II

The German Legation Transmitter

‘The problem of the German Legation Radio Transmitter was one the most difficult issues which arose between Irish Intelligence and MI5, and in fact can be said to have led to a crisis between those relations.’

COL DAN BRYAN, Director of Irish Military Intelligence (G2)

The house was a nondescript and unremarkable building, but it held within its doors a dark secret. Located inside was a wireless transmitter which was being used to covertly send messages back to Berlin. The messages were of a strategic nature regarding British troop movements, weather reports and the impact of German air raids on Britain. Local legend has it that even the innocuous-looking flower pots arranged on the window sills were strategically placed, to enable IRA members who sympathised with the Nazis to pick up and/or decode messages.

The British, through radio surveillance, had discovered the existence of illicit transmissions coming from Ireland in late 1940, but the broadcasts had begun much earlier. There were two possible origins for the transmissions: they were either from Irish republicans with radio sets communicating in Morse code, or from German or other sources in Ireland. Guy Liddell and his older brother Cecil (who served in MI5’s Irish section from 1939), in bringing up the transmitter issue with Bryan, delivered him a simple message: find the source of the transmissions or the British would be forced to take action to deal with the wireless set themselves. Realising the gravity of the situation, Bryan immediately set about locating the origin of the illegal broadcasts.

G2’s search would lead them to 58 Northumberland Road, the location of the German Legation¹ that housed the German diplomatic mission to Ireland. While G2 were relieved to have located the source of the messages and wished to make the British aware of their discovery immediately, the Irish authorities feared that it would lead to a major diplomatic problem that could inadvertently result in a pre-emptive British invasion of the Irish Free State. Meanwhile, the British fear that crucial information in relation to British troop movements and weather patterns that could be used for military planning would leak out to Berlin through the embassy was palpable, and exchanges between Bryan and the Liddells were tense.

If anything the legation issue proved that neutrality was a double-edged sword for Ireland. While it certainly kept the country out of the horrors of the Second World War, it also permitted the Germans to maintain in Ireland an espionage centre, a window into Britain that operated throughout the war and did incalculable harm to the Allied cause. In many ways Dublin was the equivalent of Casablanca or Lisbon or any of the other wartime centres of espionage. Key to this was the German Legation, headed by the German Minister to Ireland, a man who would prove to be a divisive figure in the events that would follow.

Eduard Hempel had been first sent to Ireland as German Minister in 1937. As the son of a Privy Governing Councillor he attended grammar school in Bautzen and the Fridericianum in Davos and graduated from high school in Wertheim. He completed a law degree from the University of Leipzig and following compulsory military service he joined the judiciary of the Kingdom of Saxony, but was conscripted at the start of World War i. During the war he served as a lieutenant on the administrative staff, including in the military administration of occupied Romania.

Hempel joined the foreign service of Saxony in 1920, which was absorbed into the German diplomatic service. He was posted to Oslo in 1928 but soon returned to Berlin to work in the Foreign Office. In 1928 he joined the German People’s Party, and following his posting to Ireland was pressured into joining the Nazi Party in 1938. While not a strict doctrinaire Nazi, Hempel was more than willing to carry out party policy. He was an old-school, shrewd and sensible diplomat, who had quite a detailed knowledge of Ireland, Britain and the relationship between the two countries. He was more than adequately assisted by a patriotic and well-organised staff. Hempel’s deputy was Legation Councillor Henning Thomsen, a recent convert to Nazism. The rest of the legation staff included Herren Kordt, Müller, Kochner and Bruckhaus. These men ran the legation and kept the books. The staff also included two female secretaries. Unusually, the legation didn’t have a military attaché, a common feature in other legations in neutral countries.

At the outbreak of war in 1939, Hempel became more entrenched in the legation as his position came under more scrutiny due to the deteriorating war situation, and he went to severe lengths to protect his secret transmitter. Three of the diplomats in the legation and one civil servant carried pistols, and a fifth armed man slept there each night. Bolts were placed on all the windows and a ferocious guard dog was kept on the grounds to deter any would-be intruders. Hempel was determined not to go down without a fight in the event that the Irish or British were to become aware of the transmitter and attempt to send any agents to infiltrate the legation. And he had every reason to be wary, as knowledge of the transmitter was quickly becoming widespread.

As early as 1939, a Washington press report touched on worldwide speculation about regular secret contacts between the German Legation in Dublin and Berlin. Due to the fact that international law regarding transmitters held by belligerent nations in neutral countries was so vague, Hempel, in order to draw attention away from the legation, began to encourage the use of other means of communication. This ruse was to prove short-lived, however. Despite maintaining an image of being a strict diplomat, Hempel was of course interested in liaising with whatever forces could aid Germany in the upcoming war effort.

In July 1939, MI5 agents operating in Ireland noted that a report had been received through the Czech Consul in Dublin that on 20 July the German Minister, alongside three members of the Dublin branch of the Nazi Party, had travelled to Inver, Co. Donegal to meet with leading members of the IRA. The meeting was said to have been arranged by Theodor Kordt, the Counsellor of the German Embassy in London, who had visited Ireland for that purpose. The meeting took place at the Drombeg Hotel in Inver, which was owned by an old German national named Hammersbach. One thing remained very clear to G2: despite his well-meaning disposition, Hempel was a serious threat to the Irish state following the outbreak of the war.

The legation’s increased importance as a watch post eventually led Hempel to request extra staff, and Berlin duly complied, albeit with a certain caveat. Fearful of undesirable British interest in the matter, the German Foreign Office compelled Hempel to seek the necessary papers for the extra staff, through the Irish authorities rather than through Berlin. Hempel informed the Irish authorities that he intended to fly in extra staff via a civilian plane, and furnished them with a list containing the names of the new potential staff members.

The names on the list included Hans Böhm-Tettelbach and Major Kurt Fiedler, who was to take up the role of Consul. Böhm-Tettelbach’s wife and the three-man crew completed the names on the list. Hempel was apprehensive that the conditions of Irish airports might impede their arrival, and felt that perhaps they might be better travelling by seaplane. Ever the pragmatist, he suggested that once the new staff arrived time should be allowed to pass so that the speed of his communications via the transmitter would not become noticeable. However, despite his forward planning, Hempel’s request to increase his staff created a sense of panic among the Irish authorities.

As a result of Hempel’s nefarious activities in the legation, de Valera faced a serious challenge to his policy of neutrality. If he were to concede to the Germans it might raise British and American fears, and could lead to the Allies moving against the legation and the transmitter. On the other hand, refusal could sour relations with Berlin, and would violate international obligations. De Valera’s major fear was how the American public might react to news reports of a German plane landing in Ireland with legation staff.

Hempel understood the Irish position, and felt that if they were to become aware of the true intentions of the extra staff (to encourage closer involvement between Ireland and Germany), then it would cause the Irish to doubt Hitler’s intentions towards neutral countries. Hempel visited de Valera in order to bring the matter to a head, and was told in no uncertain terms by the Taoiseach that he disapproved of the landing of German officials in Ireland.

However de Valera told Hempel that he would accept those arriving by conventional transport. This caused Hempel to try to find other ways of transporting people into Ireland. Sea routes were to prove difficult, as all passenger ships and freighters were obliged to stop at English ports due to cooperation between the Irish and the British. Sending people through another neutral country was also challenging, as Ireland had no diplomatic links with other neutral countries such as Argentina, Brazil or Spain. The idea of increasing the staff of the legation was eventually abandoned.

Despite the fraught political situation, during this period the transmitter was used in the legation on a regular basis. In the spring of 1940, Hempel advised the German Foreign Office that their prompt reporting of events in Ireland might have alerted the British to the fact that the legation had a wireless set. He knew that the British were looking for an IRA transmitter in Co. Wicklow.

His concern would prove to be well-founded. The British learned that Hempel had a quite sophisticated weather station at his house in Monkstown, and that he was able to read and forecast the weather. The fact that the German Minister to Ireland had this sort of equipment in his private residence looked extremely suspicious. However the British had a much deeper reading of the situation in Dublin than the Germans and Irish initially thought.

The British first raised the issue of the transmitter with the Irish in late 1940. They believed the transmissions were coming from the area of Laytown near Gormanstown, Co. Meath, and thus began a period of intense surveillance on behalf of the Irish authorities to try to trace the origins of the messages. The British had written to Dan Bryan through ‘the Dublin link’ between Cecil Liddell and G2, informing him of their suspicions with regard to the transmitter. In response Bryan contacted his colleague, Capt. Richard ‘Dick’ Green from the Army Signal Corps, and the two men travelled on a bank holiday Monday to Laytown in Co. Meath to scan the area for transmissions. Bryan felt the exercise to be a terrible waste of time, although he had great faith in the abilities of his colleagues in the Signal Corps. In his heart of hearts he realised that in order for any successful trace to take place a monitoring station would need to be set up on a round-the-clock permanent basis. This was mainly due to the erratic nature of the illicit broadcasts.

The fact that the Germans were operating a clandestine radio in Dublin came as no surprise to Winston Churchill, but it did give him great cause for concern. Almost every capital city in the world operated secret radio transmitters during the Second World War. Indeed the British themselves had their own secret transmitters in Stockholm, Copenhagen and Budapest, as well as many other cities in Europe. Ireland posed a problem for the British, however, in that it was the only neutral country with active belligerent legations that shared a land border with the United Kingdom. Among the various diplomatic missions active in Dublin were the Japanese, American, British and German legations. So in Dublin lay a microcosm of the major players in the Second World War. Nazi Germany had many tentacles permeating the various layers of Irish society, with the German Legation being the epicentre and direct link with the Nazi High Command.

If the German Legation in Dublin wished to communicate with Central Command in Berlin, it had a very sophisticated method of doing so, a high-level diplomatic code. The diplomatic messages Dublin and Berlin sent each other had to go through British-controlled telegraph cables, meaning the British could slow these messages down and delay them for up to a week; but they couldn’t stop them, for fear the Germans would find out. Britain was equally sending its own messages from European capitals under German control. The danger however was the fact that the legation’s radio transmissions were instantaneous, and the fact that the messages were in code made them difficult to read.

British suspicions were well placed, because in November 1940 Berlin contacted Hempel via the transmitter with a view to ascertaining the Irish appetite for German intervention in Ireland, should the British invade. In a conversation on 28 November 1940, Nazi Foreign Minister Joachim von Ribbentrop broached the subject with Hempel during the course of a very long wireless exchange. Von Ribbentrop was astute when it came to the British, having served as the German Ambassador to the Court of St James from 1936 to 1938. During this conversation he enquired whether it was possible for the German minister to arrange to see de Valera, and if so would it be possible for him to

raise the question whether the Irish would consider it opportune that you should make enquiries in Berlin about the view Germany would take of the possibility of aiding Ireland with material, etc in the case of a British attack. At the same time you could also assure them in the most explicit terms that Germany has no thought of violating Irish neutrality on her own account. But if an English attack should take place, you had personally every reason to suppose that the Reich’s government would be able and willing to give Ireland powerful support.

Von Ribbentrop continued his secret discourse with Dublin, and on 5 December he wired confidential information to Hempel asking him to broach with de Valera the possibility of a British invasion of Ireland. He advised Hempel carefully, coaching him in what to say:

You may express yourself in terms something like the following. You had information from Germany that the German government was naturally interested in reinforcing Ireland’s powers of resistance against such an eventuality. With the conclusion of the campaign in France, Germany had come into possession of a great mass of English weapons. You regarded it as not impossible in the circumstances that the Reich’s Government might be both willing and able to hand over gratis to the Irish Government a considerable quantity of these weapons, which in make, calibre, etc., are identical to those used by the Irish Army. If de Valera shows interest and you see fit you could make appropriate proposals. From a technical point of view we have no doubt, that in agreement with the Irish Government, Irish neutrality would in no case be compromised in the slightest way through this transaction.

Sensing that something was off, de Valera turned down this offer of arms and ammunition in the event of a British invasion, and von Ribbentrop did not pursue the matter any further with Hempel. The crisis was deepening, however, as the British were putting severe pressure on the Irish Department of External Affairs for information as to the location of the transmitter.

Guy and Cecil Liddell visited Dublin in an attempt to elicit more information from the Irish authorities. Sensing the Irish were not being forthcoming and perhaps holding some information back, Guy Liddell quipped to Col Liam Archer, the then head of G2, ‘of course, if you would, you could give us lots of information’. The fact that the transmitter issue arose during a period where the Germans had been victorious in the west and were having some success in the east against Russia only further compounded the difficulties faced by the Irish authorities, and left them with a simple choice: they could attempt to break the German traffic or face the wrath of the British.

Time was quickly running out. Not only was neutrality in danger, but so was the very security of the state. Such was the concern of the British that MI5 had agents in Dublin driving around in unmarked cars trying to source the origins of the illicit messages. With little immediate success being achieved, the British attitude to the ‘Irish Situation’ was becoming increasingly frayed. MI5’s efforts in locating the transmitter eventually paid off, though, and after a period of time the British felt they had sufficient proof of an illegal transmitting set being used by the Germans somewhere in the greater Dublin area. On 11 March 1941 J.E. Stephens wrote a letter on behalf of the British Dominions Office to the British Representative in Ireland, Sir John Maffey, imploring him to take the matter up with the Irish authorities:

The Authorities here now tell me that they have succeeded in obtaining technical proof of the existence of a German wireless transmitting and receiving set operating in the Dublin area.

Such was the extent of the knowledge possessed by the British that they were able to give a detailed breakdown of the broadcast frequency and the enciphering system being used by the Germans. The British knew that the Dublin transmitter was communicating with Berlin via the Grossfunkstelle Nauen transmitter station in the Havelland district of Brandenburg, Germany, the oldest radio-transmitting installation in the world, founded in April 1906. During the war the station was mainly used to broadcast to submerged U-boats via a low-frequency radio signal.

In the course of his correspondence, Stephens gave Maffey a complete technical breakdown of the radio frequency and the cipher which was being used by those operating the wireless set:

This station replies to Nauen² when the latter marked the call A.M.6. The cipher is five figures, frequency 9859kc/s. The station is located in a triangle in an area around Dublin. The signal is very weak in the country and interception is therefore very difficult. A message which the authorities were unable to read was intercepted in a five figure cipher between 1400 and 14.25 on 5/2/41. We should be grateful if you should bring these facts to the notice of the Eire authorities with a view to their taking such steps as are practicable to detect the station and prevent its further operation.

The author of the letter was careful not to draw attention to the fact that the British had a transmitter in their own legation.

You will of course bear in mind that any course of action that the Eire authorities may be asked to take must be in such form so as not to prevent the wireless transmitter that you have at your office. It might be very embarrassing if we were prevented from using this method of transmission particularly in any emergency.

In reality the British authorities in Dublin had three wireless sets and receivers, as well as a direct telephone line to London. Maffey tried to convince the Irish Under Secretary to the Department of External Affairs, Joseph Walshe, that the British would only use their transmitter in an emergency, in which case it would be advantageous for the Irish government, and that in no way could it be used in the war effort against the Germans.

The British knowledge of the German transmitter proved to be quite detailed. The Dominions Office had been informed by MI5 as to the daily frequency of messages. Transmissions were made at intervals of between 30 and 90 minutes, from 0700 up to 1430, with a further transmission at 2100. Ten messages a day on average were being passed from the control station at Nauen to Dublin via a low-powered set using a ‘skip’ frequency. This made it difficult for the British to intercept messages, though they could prove that Dublin was able to communicate often with Nauen because they would ask for various phrases to be repeated. Dan Bryan suggested that G2 could try to jam the communications coming from the transmitter, a novel approach given the increasing British discontent at what they perceived as Irish inaction.

In a secret document a few days later, on 14 March 1941, the British representative to Ireland warned that ‘if the existence of a German controlled wireless in Dublin proved a definite threat to us that the Government of Ireland must therefore be prepared for a most violent reaction if it could be proven that the Germans could transmit secret messages by wireless from Eire.’ The communiqué further stated that ‘The Eire Government would be well advised to co-operate with us in the detection of this station by asking for expert assistance from England at once.’ But the British were only engaging in bluster, and in reality were becoming increasingly anxious, as the situation became more and more fraught with each passing day.

With the pressure mounting on the legation, Hempel temporarily stopped using the transmitter except for messages that were of the utmost importance. In an intervention, Hempel had been told by Joseph Walshe that the British had provided the Irish government with details about the wireless set, including a timetable of his transmissions. Believing that the Irish would not act in relation to the transmitter immediately, Hempel set out a number of protective measures to safeguard the legation and the transmitting set.

From the spring of 1941, it was decided that all messages would be sent on secret, predetermined frequencies to avoid giving the impression that the legation was contacting German war units, ships or planes in the vicinity of Ireland. Hempel also ensured that all transmissions were shortened, and that regularly scheduled reports were eliminated if there was no important news, which could be indicated by sending a code earlier the same day. It was also agreed that all transmissions should be scheduled at various times, with the recognition signs changing daily.

In addition to this, more wires were sent to Washington for recoding and forwarding to Berlin. Suspecting that the British knew about the transmitter, Hempel considered moving it to his house in Monkstown, and in a further precautionary measure he contacted Berlin warning them to transmit only in emergencies. When circumstances warranted the risk he assured the German High Command that he could disguise a message by making it harder to decode or confusing the code with signals sent from planes and submarines.

But despite Hempel’s best efforts, the Irish authorities were now prepared to act. De Valera had begun to give serious consideration to dealing directly with the German code. Having trained as a mathematician and having taught in various Dublin schools, including Belvedere College and Castleknock College, de Valera had a rudimentary knowledge of the mathematical and cryptographical work that would be involved in breaking the legation’s code. After careful consideration, the Taoiseach felt that Ireland should attempt to break the German traffic, because of the severe threat it posed to national security. He was concerned that the Germans might be considering using Ireland as a springboard to attack Britain, but he equally feared that the British would force him to take action against the legation directly. Eager to observe the strict protocols of neutrality, de Valera informed Hempel that the British probably knew about the transmitter. However he did not tell him that the British and Irish had shared this information.

Deeply worried about the situation at hand, the Taoiseach turned to G2 to help provide a solution. The Irish Army had no codebreaking capacity, and indeed felt that breaking the code would be impossible unless it was attempted by a large team, but Dan Bryan had a plan. He immediately put the legation under constant surveillance from Beggars Bush Barracks, which was only separated from the legation by a lane. And, unbeknownst to anyone, Bryan had an ace up his sleeve, one which would come from the most unlikely of quarters.

In Sandyford, Co. Dublin, the Director of the National Library of Ireland, Dr Richard James Hayes, answered a late-night phone call from a familiar voice. It was Col Dan Bryan, and as Hayes listened intently, he knew that his life was about to change forever. He hurriedly volunteered himself for the work offered by Bryan, and as Hayes put down the phone his wife Clare turned to him and asked, with trepidation in her voice, ‘Is everything alright, Jim?’ As he looked at his wife, the enormity of the phone call dawned on Hayes. He, a librarian, aesthete and young father, was now all that stood between Ireland and Nazi Germany.

Bryan felt that Hayes was the best person to lead a unit to attempt to break the traffic coming from the German Legation. Hayes had worked for G2 prior to the outbreak of war in 1939, but it remains a mystery how he had first been recruited by Irish intelligence. It has been speculated that Hayes and Bryan first became acquainted during the War of Independence as active volunteers in Michael Collins’s Intelligence section of the IRA. This has been discounted by Hayes’s family, though, as they maintain that Dr Hayes would have been a young man studying in Clongowes Wood College in Clane, Co. Kildare, during the War of Independence, and had no involvement in republicanism whatsoever. However it was that Hayes had first become acquainted with Bryan, one thing is clear: Bryan had full faith in the intellectual capabilities of Hayes.

Despite his prominent role in Dublin society, Ireland’s National Librarian and soon to be master codebreaker came from very humble beginnings. Richard James Hayes was born in 1902 in Abbeyfeale, Co. Limerick to Richard James Sr, a local bank manager from Co. Clare, and Katherine Hayes, from Ballymahon, Co. Longford. Hayes Jr spent his early childhood in Claremorris in Co. Mayo. His time there had a profound effect on him, and for the rest of his life he considered himself a Mayo man. He had an older brother named Ambrose, named after his grandfather, as well as a baby sister who died at birth.

Richard Hayes Sr died in 1920, when Richard Junior was 18 years old. Unable to avail of any financial compensation, the family lost their house and moved to Dublin. Soon after, Ambrose ran away from home, and was only seen sporadically afterwards. This left young Richard as the sole carer of his mother. Despite such difficulties at such a young age he excelled academically, winning a scholarship to study in Clongowes, where he was a classmate of Tom McQuaid, a brother of future Archbishop of Dublin, John Charles McQuaid. Indeed, the Hayes family became very friendly with the McQuaids as a result, ironic given the fact that Richard was a lifelong atheist.

A distinguished student, Hayes won an academic scholarship to study at Trinity College Dublin in 1920. He studied for three degrees simultaneously, and in 1924 he graduated with first class honours in the three Bachelor of Arts degrees: Celtic Studies, Modern Languages and Philosophy. In 1936 he further bolstered his academic credentials by obtaining a Bachelor of Law degree, as well as a doctorate. Shortly after graduating from Trinity, Hayes was appointed Assistant Librarian at the National Library of Ireland in 1924, eventually succeeding Richard Irving Best, who had been immortalised in James Joyce’s Ulysses.

Hayes became the fifth Director of the National Library in 1940, and upon taking office he held the distinction of being the youngest man appointed to the post since the library’s foundation in 1877. His first major work, Comparative Idiom: an introduction to the study of modern languages, was published in 1927. Another work was published in 1938 (co-edited with Bríd Ní Dhonnchadha), Clár Litridheacht na Nua-Ghaedhilge, an index to poetry and prose in three volumes that appeared in a series of periodicals associated with the revival of the Irish language. Such was the importance of the index that it is still being used today.

Hayes was also an avid fan of rugby, and wrote a book on the sport. In 1928, Hayes married Clare Columba Keogh from Cabra, and the couple rented a small adjacent flat there, where their first son Bertie was born in 1929. Hayes also rented a small flat for his mother to stay in. The young family soon moved to the south side of the city, settling at 18 Sandford Terrace in Ranelagh. During this time Hayes began editing the Irish Motorcycle Guide Annual and the Irish Rugby Football Union annual guide. While Hayes had a quiet and reserved manner, he possessed an abounding sense of humour. On the birth of Bertie, Richard jokingly wrote an invoice on Irish Motorcycle Guide-headed paper to his mother. His joy and trepidation at becoming a father were evident:

INVOICE: The goods referred to in our letter of December last have been delivered in good condition.

SPECIFICATION: Date of Arrival: 11AM 1st January, Sex: Male, Weight: 7½ lbs, Hair: Long Brown, Face: Chinese Type, Health: Excellent, Lungs: Loud, Observations: Help!

The S.S. Clare was safely brought into port and is now very comfortable at the anchorage 29 Upper Mount Street. The voyage was an exceptionally calm one and was not buffeted by the high seas which are usual at this season. The ship is due to leave her anchorage to sail for Ranelagh within a week.

Signed: Richard J. Hayes (Captain)

Four more children were to follow: Joan born in 1930, Mervyn in 1932, Jim in 1942 and Claire (whom he nicknamed Faery) in 1943. The family eventually moved to Sandyford, where Hayes built a property named Thornfield situated on four acres, building a tennis court and swimming pool for his family on the site. Hayes spoke several languages fluently, including Arabic, French, Italian, Irish and German. Besides his obvious intellect in the field of linguistics, Hayes also had a fondness for mathematics and, according to his daughter Faery, he was excellent at crossword puzzles, recitations and monologues. Always impeccably dressed, he was rarely seen without his beloved Trinity tie and a modest wristwatch. According to Faery he disliked expensive wristwatches, often saying that ‘a watch is there to tell the time, that’s all’. Hayes always carried with him a small tin of cigarettes and would enjoy a smoke while working on the complicated German codes he intercepted.

His skill at crossword puzzles was useful, as speed at completion of crosswords was used by MI5 as a recruitment method to the Government Code and Cipher School at Bletchley Park, where Alan Turing broke the Enigma code. One of the skills required of codebreakers was to be able to solve a crossword in more than one language in a set period of time.

Dan Bryan knew that Ireland’s role was not to outfight the Germans in terms of the transmitter but to outsmart them and to share the crucial information with the British and other Allied Powers. In Hayes he now had a valuable secret weapon.

After naming Hayes to lead the unit to break the German code, Bryan and his superiors assigned him a team of people who were thought to have mathematical capabilities, or who were interested in codes. These included a number of individuals, some of whom have been identified and others whose identities to this day remain unknown. Among the men recruited by G2 to help Hayes were a man by the name of Lennon, who was the head of the Patents Office in Dublin, a chief superintendent in An Garda Síochána, and three military personnel (though the two civilian members were soon released from their duties).

The three remaining members were Conn McGovern, who had just been commissioned in the Army and held a master’s degree in mathematics; a non-commissioned officer named Plunkett McCormick, who had trained as a solicitor and was later commissioned in intelligence; and Kevin Boland, an engineering graduate from University College Dublin and son of Minister for Justice Gerald Boland who was himself later a government minister and key figure in the Arms Trial of 1970. Such was the clandestine nature of the codebreaking operation that each member of the team was sworn to secrecy. Boland was told to not even tell his father.

The team were given a room to work in at Beggars Bush Barracks, where a wireless unit recorded incoming and outgoing traffic from the legation, and this operation continued for a period of a few months. The legation transmitter issue had caused such consternation between the British and Irish authorities that communications between MI5 and G2 broke down for several months. In the interim a large number of organisational changes took place within the army structure; Col Liam Archer was promoted from Director of Intelligence to Assistant Chief of Staff, and in June 1941 Dan Bryan succeeded him as the head of G2.

Hayes and his team worked feverishly on the legation code, and after a considerable period of time Hayes was able to obtain a highly sophisticated reading of it, but he feared that attempts to break it and read the traffic would prove fruitless. He also felt that the men he had been provided with were slowing him down:

I asked for two or three men with high University qualifications in science or mathematics. The help requested was not forthcoming and I was instead given three lieutenants of clerical grade ability. These men were useful for tabulating material and compiling statistics but had no special ability for cryptography.

Indeed the bulk of the codebreaking work was being carried out by Hayes alone, as the men assigned to him were really only of basic ability, and were ill-equipped to deal with the sophisticated workings of the German diplomatic enciphering system.

Hayes’s attempts to break the system were detailed and arduous, requiring a wealth of knowledge of codes, ciphers and keys. In the field of cryptography a cipher is a mathematical algorithm used for performing encryption, involving the substitution of letters for numbers in a varied sequence. Enciphering has been compared to putting a message in a locked box to which only the sender and receiver have a key, which is usually a number or a word used to transform the message into an incomprehensible sequence of letters and numbers.

Various kinds of ciphers and keys have been used throughout the centuries, and until the computer age it was widely considered something of a black art. Crucially, there would always be a codebook to go with the keys, with which the message could be decoded. The most basic version of a cipher is a substitution cipher whereby, for example, the letter ‘A’ might be replaced by ‘B’ and ‘B’ might be replaced by ‘C’, and so on, thus making the message incomprehensible. However, despite its advantages such a method wasn’t without its faults. For example the letter ‘E’ is the most commonly used letter in the English language. Therefore a codebreaker need only look for a repeating number or letter in the message until he or she comes to the conclusion that that number or letter likely corresponds to the letter ‘E’.

To counter such a weakness, more complicated ciphers were developed. For example one letter could be encrypted using one sort of substitution and the second cipher could be encrypted using a different substitution. That would virtually prevent ‘E’ from being the most common number or letter in a given message. During the war the Germans took the process a step further, using what is known as a ‘polyalphabetic cipher’, an encrypted message using multiple alphabets. If such a cipher were used there could be literally thousands of possibilities in terms of solutions. In a further attempt to confuse any would-be codebreakers, the Germans deliberately put in spelling errors into keywords, as well as ‘nulls’ or spaces. This made codebreaking without the codebook an extremely difficult endeavour.

Ciphers are only successful if the people making them know they’re secure, and the Germans were hugely confident that their ciphers were extremely secure during World War II. In the 1920s Germany had moved into mechanised cryptography, the use of encryption machines to generate coded messages – creating the Enigma machine, for example, which had 150 quintillion keys. If they suspected that they were being broken into they could change them ever so slightly to lock the Allies out. Hayes had studied the work of his predecessors in America during World War I such as Herbert Yardley and William Friedman, and he was in many ways more prepared than the Germans were.

He was able to ascertain, starting with the knowledge that diplomatic codes were based on codebooks or machines, that the legation code was very sophisticated in its nature. He felt that it wasn’t of the simple dictionary codebook type, and that in the absence of a machine for calculations more manpower would be needed if he were to have any hope of breaking the code. Writing to de Valera, Hayes reported,

The transmitter messages are so designed that statistics compiled from thousands of telegrams show an almost perfect uniformity of the figures or letters used. Nowadays they are unbreakable unless the instructions for their use are not complied with or from information from inside. The extent to which diplomatic codes are purchased or secretly copied is much greater than is generally believed. We have much to learn in this respect. Matters of this kind must, of course, be prepared years in advance.

Hayes’s efforts at breaking the code, though extensive and exhaustive, were unsuccessful, but they were not in vain, as he was able to devise a method for dealing with machine-based codes which he felt could be useful in the future. In a letter to de Valera commenting on his efforts he speculated that

It is not certain whether the German Diplomatic code is based on a code book or a machine. It is almost certain that it has not been broken by the British or Americans. It is now known that that the contents of many of the cables from the German Legations throughout the world were available to the British or Americans – within three to four days of their arrival to Berlin. This was achieved by accepting the help of an official in the German Foreign Office who offered his services. The British refused to deal with him, but the Americans made a deal and this source worked every day for them. After checking the information received through this channel for six months and finding it accurate in every respect, the Americans used it to get all the reports of the German Minister in Tokyo. This proved invaluable for the war in the Far East. It was not possible to get all the copies of all the reports of all the legations but at any time any particular report could be obtained. The inside information from the Far East was of such value that instructions were sent to the source to concentrate all his time and efforts on reports from that theatre. It should be noted that on any given occasion or for any special reason, this inside source could have been used to get copies of messages from the German Legation in Dublin.

While Hayes worked on decoding, Dan Bryan and G2 utilised their military powers to further remedy the grave situation. Gardaí were used to protect German diplomats visiting the legation, and this gave G2 extra eyes on the ground. Indeed such was the level of concern that the transmitter would be used to leak information that military intelligence considered approaching a servant who worked in the legation through a newspaper editor, a prisoner of war in Germany during the First World War who was familiar with the personnel and routines of the Dublin legation. However this plan was abandoned when it was feared that the servant would complain to the minister. But someone acting on their own made overtures to a maid who had been recently dismissed from her job at the German Minister’s residence in Monkstown. Some newspapers of the day claimed that Intelligence was responsible, and that the maid should be compensated, though the claim for compensation was eventually refused by G2.

Despite his best efforts, Bryan and his men were unable to infiltrate the German Legation, but there were others who were able. The London-based Czech government had planted an agent there who succeeded in bugging the building with various listening devices placed in strategic locations. On one occasion at the beginning of the war, German Minister Eduard Hempel and Irish Under Secretary to the Department of External Affairs Joseph Walshe went into the garden of the legation for a cup of coffee. The Czech agent directed them to a table near a bush. A few weeks later Walshe, to his shock, received a report of his conversation from MI5. Afterwards, the Czechs decided to remove their agent in order to protect Ireland’s diplomatic position. G2 also tapped the legation telephone, and some would-be collaborators were apprehended as a result.

One such person was a Dutch fascist named Jan van Loon, who had deserted from the Dutch Navy serving under the British Admiralty. Van Loon had crossed from Northern Ireland into the south, making his way to Dublin. With him he carried sketches of British convoy layouts, which he tried to bring to the attention of staff in the legation. He was apprehended by the Gardaí, and the sketches were used as evidence to intern him until the end of the war. While he was in prison he would befriend other non-nationals who were recently apprehended with whom he shared common cause.

Despite the level of surveillance he was under, Hempel was able to keep Berlin regularly informed on military conditions in Ireland. He noted that the Irish were emphasising public instruction in air raid and gas attack defence, and that de Valera wanted to increase the Defence Forces budget in order to modernise the army to deal with the possible threat of invasion. Berlin was also aware that de Valera wished to purchase arms from Sweden and to expand the 6,000-man army, and by August 1940 a recruitment campaign had seen over 170,000 men enlist. While the leakage of sensitive information about the Irish was a problem, any leaks in relation to Allied activities posed a huge threat to the outcome of the war, and G2 became greatly concerned about information leaking out of Ireland that the British didn’t want to fall into the hands of the Germans.

In July 1940, the Abwehr held a conference in Kiel in northern Germany, during which it was decided to begin an espionage campaign against Britain involving intelligence gathering and sabotage. German agents were sent to Britain in a variety of methods – some parachuted or landed via U-boat; others entered the country on false passports or posed as refugees. In order to counter this, the British began a system of counter-espionage known as the Double-Cross (XX) system, and they achieved outstanding results from its use. The Double-Cross was an elaborate system of detaining German agents and turning them into double agents who would then be of use to the Allies. Germans or other nationals who were compromised in one way or another were usually selected for the programme.

Ultimately the Double-Cross system became a weapon of deception against the Germans, and the British used it to plant misinformation about British strategic plans among the German agents they controlled. This was of huge significance, as the Americans were working alongside their Allied counterparts with the intention of invading mainland Europe. At this stage Britain had such a control of German espionage that they were able to use compromised agents to spin an erroneous version of events about the Allies’ next moves. Therefore Ireland became hugely important from a strategic point of view. The British were adamant that they didn’t want information coming out of Ireland that would call into question the information that the German agents controlled by MI5 were relaying back to Germany. Any information, true or false, that the British hadn’t generated themselves could have disturbed the very detailed picture that the Allies were trying to paint.

Meanwhile in Germany the Abwehr was making plans to curtail the attention that the transmitter was attracting. By February 1941, the Chief of German Military Intelligence, Admiral Wilhelm Canaris, declared that weather reports were no longer needed. Canaris felt that similar information in relation to weather could be obtained from other sources, and he ordered that all transmission be cut down with immediate effect. Matters worsened when two German battleships, the Scharnhorst and the Gneisenau, escaped a British blockade of Brest in a snowstorm. The British press claimed that the Germans had acted on intelligence received from Dublin, bringing matters to crisis level.

The Allies contacted de Valera in order to bring the matter to a head. Eager to protect plans for the imminent invasion of Europe, they duly put pressure on de Valera to have the transmitter removed from the legation. Eventually Hempel conceded, and the wireless set was put into a suitcase, which was then placed in a steel casket and deposited in a safe at the Munster and Leinster Bank. Only Hempel had the key to the suitcase, though both Hempel and Justice Minister Gerald Boland could open the steel container. Only the four bank directors could open the safe.

Despite these developments Hempel believed that the radio would be returned to him in the event of an Allied attack. He also tactically decided that it was necessary to move the transmitter as it helped the maintenance of good relations with de Valera, and as such was a necessary evil. During this period Hempel also refused to have another set parachuted in to him, for fear it would give the British and Americans a pretext to invade. The transmitter and presence of the German Legation in general were to prove a huge thorn in the side of Churchill, who wrote in a secret personal minute in 1943:

I think we must endure this abominable state of affairs for the present. The entry of the United States into the war has changed the picture, and it may be possible to take stronger action against Southern Ireland and force them to dismiss the enemy representatives they harbour. Their conduct in this war will never be forgiven by the British nation unless it is amended before the end. This in itself would be a great disaster. It is our duty to try and save these people from themselves. Any proposals which you make to terminate the enemy representation in Dublin will be immediately considered by me. We ought not to shirk the difficulties unduly for the sake of a quiet life. There seems to be a very strong case for doing what is right and just and facing the usual caterwaul from the disloyal Irish elements in various parts of the Dominions. I shall take advantage of my visit to Washington to discuss the matter again with the President. I am quite sure that the opinion of the House of Commons would be overwhelmingly favourable.

Churchill’s attitude was to place considerable pressure on Bryan and the Irish authorities who, perhaps more than de Valera, realised the increasingly alarming state of affairs that the Irish nation was facing. The unfolding events were to strengthen Bryan’s resolve that it was in Ireland’s best interest to cooperate in the sharing of information with the British in order not only to preserve neutrality but to protect the very sovereignty of the state itself. Ultimately the British authorities saw two courses of action available to them to solve the legation issue: they could either seek the expulsion of the German Legation from Éire or compel the Irish government to seek the removal of the wireless set from the safe, to which Hempel had a key.

The British assumed that de Valera would seek proof that the Germans were engaged in espionage before he would seek to expel the legation from the country, and while the British thought that they did have proof, they felt that revealing it would compromise their most secret material. The only course of action available to the British was to prove that the legation had used its transmitter at a time of impending British operations, where it could be surmised that the legation was sending urgent intelligence to Germany. The British were aware that Hempel sought to recruit another wireless operator whose ‘touch’ would be unrecognisable to the British. The gentleman in question was Feldwebel Hans Bell, and alarmingly the British speculated that the Irish authorities had agreed in principle to Bell working in the legation as an assistant at cipher work. The British thought that if he was employed and his qualification as a wireless operator became known, this would give them a pretext to make a démarche through the British representative in Ireland. In any case the situation was now becoming very serious.

By 1943, plans were already underway for the invasion of Europe, and both the American and the British authorities were concerned that any information leakage from Dublin could have a detrimental effect on invasion plans. Hempel continued informing Berlin of various details in relation to the Air Force and Navy. He estimated that the Air Force had been increased from 40 planes to 170 regular aircraft and 12 seaplanes. Despite the fact that Ireland possessed a few armed patrol boats rather than a fleet, harbour forts had been strengthened with heavy artillery and a new coastal defence force consisting of experienced seamen.

The Irish defences were lacklustre at best. All forces lacked light weapons such as hand grenades, which the Irish could not manufacture and the British could no longer provide to them. Hempel was able to provide the German High Command with information about the British, however. In July 1942 he reported that a Vauxhall tank factory employing 15,000 workers was operating 50 km from London. Adjacent to this was the Percival Aircraft Company, with 3,000 workers and 200 inspectors, as well as various factories which manufactured arms and munitions for the British war effort. Hempel estimated that that about a million Englishmen and 100,000 Americans were stationed in southern England in June of 1942, and that 60,000 or so Americans had remained in Northern Ireland after almost all of the British had left.

Hempel further informed Berlin that the Americans were producing planes on a large scale. These were mainly Liberators, B-24S flying across the Atlantic to Foynes, Co. Limerick, on the Shannon estuary, then continuing on to England or Lisbon. During the war the Liberators were the only air contact that Ireland had with the rest of the continent, and Berlin requested that Hempel obtain more detailed information on the planes. He deduced that they were produced by Ford and Kaiser, and were likely to see bomber duty as well as transporting passengers between Canada and Britain. He also relayed that England was building poison gas-proof shelters as England feared German gas attacks, but despite this sign of trepidation he also reported that the general English population seemed confident that the Allies would eventually win out. This was generally attributed to Allied victories in North Africa and Sicily, and the British and American capacity to wreak large-scale destruction on German cities.

Hempel gave detail as well on the activities of the British Eighth Army. He garnered much of this information through conversations with indiscreet members of the Eighth Army who were on leave in Ireland. In one case a sergeant major gossiped to a friend who held radical nationalist views, and the information was then passed to Hempel through an intermediary. More tellingly, Hempel became aware of reports that an artilleryman on leave from the Eighth Army in Ireland spoke of preparations for a great battle in Italy. The gentleman recounted:

As regards the forthcoming invasion of the continent, while preparing for a breakthrough in Italy men were suddenly embarked for England with the greater part of the British contingents of the 8 Army. The attack from England is to begin in February. Heavy losses are expected.

Other items of information sent to Berlin resulted from conversations with a Canadian pilot on leave in Ireland who was member of a parachute brigade transferred to England from Italy.

How much value can be attributed to Hempel’s information is debatable. He was closely monitored by G2, and the British kept feeding him false information. It is believed, however, that he was aware that he was being watched, given his extreme caution in dealing with people who offered their services to him. While the British were able to slow down and read cable communications, the transmitter was seen as an uncontrollable source of information leakage which they sought to compel the Irish authorities to deal with conclusively. To that end it was decided that the transmitter would be removed from the bank by G2. The job was given to one of the Signal Corps’ most trusted recruits.

The transmitter was eventually picked up by a Junior Military Intelligence Officer named John Patrick O’Sullivan, a native of Valentia Island in Co. Kerry. O’Sullivan had previously worked with the Marconi Company before joining the army, and was therefore adept at the intricacies of wireless communication. In 1915 O’Sullivan had trained a young Michael Collins in telegraphy in the Marconi School in Cork and had joined the Army’s Signal Corps many years later at the invitation of his old pupil in July 1922. Prior to joining the army he had an extensive career with the Mercantile Marine as a telegraphist and radio officer. In 1917 his ship had visited Halifax, Nova Scotia, and had a narrow escape when a French ammunition ship exploded in the city’s harbour just as his ship dropped anchor outside the bay. The disaster claimed 2,000 lives and destroyed much of Halifax.

O’Sullivan had been transferred to Military Intelligence at the beginning of the war, and he and others set up a monitoring station at GHQ in Collins Barracks to listen in to illicit transmissions and to record them for deciphering. The group that reported directly to Dan Bryan included O’Sullivan, Commandant Seán Nelligan, a school teacher called Joe Sweeney and Eugene O’Connor, a former Jesuit priest seconded from the Department of Defence. The group were also aided by a professor of Spanish at University College Cork, Joe Healy, who had himself been seconded to Military Intelligence for the duration of the war. By this stage G2 had developed a system for the detection of illegal transmitters in the Dublin area. Frame aerials were attached to vans which were then driven around areas which were suspected to contain illegal wireless sets. The aerials were able to detect signals within a three-mile radius, and by using separate vans in up to 17 different locations in the city, G2 were able to triangulate the location of illegal transmissions and subsequently act on them.

O’Sullivan also volunteered to set up another monitoring station at his home in Chapelizod, where he worked ‘off duty’. As a result his home was protected round the clock by two military policemen, who routinely kept an eye on the listening equipment he stored in a shed at the back of the house.

Such was the group’s success that most if not all of the illegal spy stations in Ireland were intercepted, and the equipment being used by belligerents was also confiscated. After the legation transmitter was confiscated O’Sullivan and his officers placed Hempel under house arrest.

Using his expertise in telegraphy, O’Sullivan discovered that messages were being transmitted from a station near Berlin to Ankara, Madrid, Lisbon and Tokyo. O’Sullivan gained such an understanding of the transmitter that he was able to spot even the slightest variation in the broadcasts being sent, allowing him to deduce, in one instance, that Berlin had been hit in a bombing raid. This was later proven in statements sent out by the German Foreign Office, confirming that a thousand-bomber raid had taken place the previous night.

O’Sullivan shared this crucial knowledge with his colleagues in G2, and it would later prove invaluable to Richard Hayes and MI5 in their efforts to break the legation code. O’Sullivan’s group’s most notable success was the breaking of the ‘Barbarossa Code’, which was being transmitted in geometric progression using a polyalphabetic substitution system. The coded transmissions outlined plans for Hitler’s invasion of Russia, and while G2 shared this information with the Allies they did not accept this until the Germans invaded Russian territory on 22 June 1941. They continued to supply crucial information to the Allies, and such was the success of their work that in 1945, at the end of the war, both Truman and Churchill thanked de Valera for the work carried out by O’Sullivan and his group. John Patrick O’Sullivan retired from the Army in 1946, having reached the compulsory age for retirement at his rank, and went on to a successful career with Kenny’s advertising agency in Dublin and the Lep Transport Company in London. He died in 1977 and is buried in Palmerstown Cemetery in Lucan, alongside his wife Mary.

By August 1944, Hayes had carried out a detailed investigation of the German diplomatic code. This investigation was founded on the idea that the code being used was based on a machine. Hayes worked out a mathematical system that allowed the code to be tested for the more probable possibilities. Each test involved the solution of 219 equations for nine unknowns, and from this Hayes concluded that it was theoretically possible to break the code. The nine tests also each necessitated three weeks of intensive work, which could not be interrupted for more than a few hours if the mathematical thread of the argument was not to be broken. To further complicate matters, any mistake rendered the whole operation useless, and it would have to be started all over again from scratch. Hayes felt a staff of five competent mathematicians might have achieved a result in three to six months.

Eventually, towards the end of the war, Hayes and his staff, working with G2 in conjunction with MI5, managed to break the legation code using a myriad of resources. Such was the fear of information leakage that the British prioritised the breaking of the Dublin code over that of other embassies and legations active during the war. While it had taken a considerable amount of time to break the code, Hayes’s attention in the interim was elsewhere. He and G2 were busy dealing with an even greater threat.

1In diplomacy, a legation was a diplomatic representative office lower than an embassy. Where an embassy was headed by an ambassador, a legation was headed by a minister. Ambassadors outranked ministers, and had precedence at official events. Throughout the 19th century and the early years of the 20th century, most diplomatic missions were legations. An ambassador was considered the personal representative of his monarch, so only a major power that was a monarchy would send an ambassador and establish an embassy.

2The Nauen Control used a series of operating signals in the AM frequency. These consisted of lettered codes beginning with the letter ‘X’ in the case of the German Legation Transmitter.