A history of British SIGINT (#1); the origins, 1850-1918
From the Second Boer War to the First World War
TL;DR
This newsletter is the first in a series covering the history of British signals intelligence (SIGINT). It looks at how SIGINT emerged, its initial development during the Second Boer War and the success it had during WWI.
Here are the key takeaways:
SIGINT may have significantly matured during WWI, but it did not begin at that point. SIGINT was a practice starting to develop during the 1850s, and was first put to the test during the Second Boer War between 1899 and 1902.
SIGINT operations during the Boer War were not that advanced. However, it provided a glimpse into the value of such intelligence, and this combined with the growth of radio encouraged Britain to grow its SIGINT capabilities.
By the time WWI came around in 1914, Britain was well-positioned to deploy its SIGINT operations. The advantages it gave the British during the conflict was fairly consistent, and saw its intelligence community grow very quickly.
The most important contribution British SIGINT made to WWI was the interception and decoding of the infamous Zimmermann telegram. This act, which revealed German plans to engage in submarine warfare in the North Atlantic and its proposal to Mexico for a military alliance, would bring the US into the war and help secure an Allied victory.
WWI proved crucial for the development of British SIGINT in numerous ways. This includes the utilisation of cable networks and the private sector, the establishment of MI5 and MI6, the advancements in both interception and codebreaking, and the importance of capturing codebooks to enable the deciphering of encrypted messages.
What is SIGINT?
Simply put, signals intelligence (SIGINT) is the practice of extracting information from intercepted communications.
A more sophisticated definition is provided in s.3(1)(a) of the Intelligence Services Act 1994, which spells out the function of the Government Communications Headquarters (GCHQ) as the agency responsible for British SIGINT. That provision states that the function of GCHQ is to:
...to monitor, make use of or interfere with electromagnetic, acoustic and other emissions and any equipment producing such emissions and to obtain and provide information derived from or related to such emissions or equipment and from encrypted material...
Today, much of SIGINT is obtained via cyberspace. Because of this, almost everyone with access to the internet could be subject to SIGINT operations by GCHQ and other intelligence agencies around the world. The proliferation of the internet and the communications it conveys has led to a perception of mass surveillance, whereby the state is able to tap into and collect any communications or information that it wants, whenever it wants, however it wants and from whoever and wherever without limitations or constraints. The prospect of such mass surveillance received particularly widespread attention in 2013 after the Snowden revelations.
Why write about the history of SIGINT?
The Snowden revelations are what got me interested in the data rights space. It highlighted the importance of the happenings in the intersection between technology, the law and society. In other words, it highlighted to me how technological development has a significant impact on our wider society, and it is important to understand the risks that arise from this and how we deal with those risks to ensure a healthy and well-functioning society.
However, I felt that the Snowden revelations put a lot of focus on the regulation of SIGINT and how our security and intelligence agencies (SIAs) carry this out. And rightfully so of course - the revelations exposed the unlawful intelligence operations of the US and UK SIAs, in particular the NSA and GCHQ respectively, which eventually led to an improved legal framework (though it is far from perfect).
But an aspect of the debate that I think was missing was the importance of SIGINT and why it even exists in the first place. This does make sense in way, since the SIAs enjoy a great deal of secrecy and exclusivity regarding their work. Cf. from What even is national security?:
There are two key elements to the veil of national security:
Secrecy
Exclusivity
The first key element is about national security matters being protected from public eyes and therefore barred from public discussion. Such secrecy applies to information about national security threats, the methods used to combat them, and anything else that is relevant to these operations.
Secrecy is maintained by the 'neither confirm nor deny' (NCND) policy. This is a principle that the government will not confirm nor deny the accuracy of information related to national security matters if doing so would damage national security.
When invoked, the government will not respond to questions, claims or allegations about its national security work. This policy has been used in Parliamentary debate and in court proceedings.
The second key element is about matters of national security being solely reserved for the government and its agencies. This means that it is not for the courts or the legislature to decide which threats to prioritise and how they should be addressed.
Exclusivity is maintained by the separation of powers. This is a long-standing public law principle that the institutions of the state (the executive, the legislature and the judiciary) should be functionally independent.
This means that none of these institutions should be able to exercise the powers of the other. Only the executive can execute national security policy, only the legislature can pass national security laws, and only the judiciary can provide legal judgments on national security law and policy.
The rationale for secrecy and exclusivity is the operational efficacy of national security. Both elements contribute to this efficacy in different ways.
Secrecy prevents adversaries from learning about the measures used against them by the state and adapting their behaviour accordingly. Exclusivity ensures that national security decisions are made by agencies with the relevant information, resources and expertise.
These ideas were explored in the Zamora Case in 1916. This case concerned whether an order could be made by the government to requisition a neutral ship carrying contraband (copper) during wartime.
It was determined that such an order was illegal. But even in making this judgement, the House of Lords made reference the veil of national security.
On secrecy, it was asserted that matters of national security should not be “made the subject of evidence in a Court of law or otherwise discussed in public.” On exclusivity, it was asserted that “those responsible for the national security must be the sole judges of what the national security requires.”
Justifications have therefore been made for the veil of national security. It ultimately provides agencies like GCHQ and MI5 the opportunity to do their job effectively.
But another consequence of the veil is that it makes it more difficult to determine what national security actually is. It can distort what constitutes a national security threat and how they should be addressed.
This in turn complicates the scrutiny and accountability of government agencies responsible for executing national security operations. It is hard to critique the work of these agencies when their internal workings are largely inaccessible.
This has driven me to better understand the work of the SIAs, and in particular the work of GCHQ as the agency responsible for British SIGINT. I have always thought that a better understanding of this would provide a sound foundation to develop appropriate legislation covering such activity. By looking at the historical evolution of British SIGINT in particular, we can see how the capabilities of SIGINT have changed over time and the associated policy implications this has had.
Accordingly, this series aims to explore that historical evolution, starting with this post which covers the beginnings of British SIGINT in the 1850s and its eventual maturation during WWI. I will do so with the help of several books on the subject, including but not limited to:
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016)
Paul F Scott, The National Security Constitution (Hart Publishing 2018)
John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020)
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023)
The Second Boer War
The beginnings of British SIGINT did not take place during WWI.
Many cite 'Room 40' as the start of such operations. Established in 1914 at the beginning of the war, this codebreaking unit within the British Admiralty was an important precursor to the "many scientific methods used by Bletchley Park two decades later."1 It was around the beginning of WWI that the value of codebreaking was really getting its recognition,2 as the agency was able to decrypt German codes and give the British advanced knowledge of the movements of the German Navy.3
But even as GCHQ admits, whilst Room 40 marked the start of the most significant developments in British SIGINT, the use of such intelligence in wartime dates back to the late 19th century, when the collection of secret intelligence regarding foreign threats through interception and codebreaking started to become more important.4 This was when British intelligence agencies were first established:
The War Office (a government department responsible for the administration of the British army between 1857 and 1964) set up the Intelligence Branch in 1873. This agency was responsible for intelligence gathering and planning.
The Admiralty (another government department responsible for the command of the Royal Navy from 1707 to 1964) set up the Foreign Intelligence Committee in 1882, and eventually evolved into the Naval Intelligence Department (NID) in 1887.
Even with these institutions in place, interception and codebreaking were practices only used occasionally by the British between 1844 and 1886.5 SIGINT was not considered to be important. However, the rise of telegraphic communications would soon change this:
States could intercept and solve the encoded telegrams of foreign governments in times of peace and of war. This of course, was not easy. Such traffic could be solved only if the codebooks were surreptitiously copied or were reconstructed through observation and inference, by means of the slow and painful 'process of the probable word'.6
An important advantage Britain had in this context was the Victorian telegraphic cable network (see the image below) which spanned across the globe and with Britain playing a central role since the 1850s. The British led the development of the technology used to build the submarine cables that formed part of this network. Much of this was down to Britain's control of Malaya (now Malaysia) which was where a natural rubber called gutta-percha could be found. This material was crucial for the development of undersea telegraph cables, monopolised by the Gutta Percha Company which produced 2,400 km of gutta-percha insulated core between 1851 and 1852. This activity was spurred on by the British government's desire to be able to communicate more quickly and efficiently with the different dominions across the empire.

The British government also placed numerous cable censor officers at different points of this telegraphic cable network. The War Office proposed a new programme to "censor all messaging passing over [telegraph cables] in wartime" using expert decyphering by the chief censor in London "who would examine every encoded telegram which was intercepted by the censorship."7 This also included a proposal to tap London-Paris telephone lines, "one of the earliest known references to the strategic value of the interception of international telephone communications."8 This was bulk interception in all but name, and "entire British Empire, sprawling across more than half of the globe, served as an intelligence machine - a veritable 'empire of intelligence'."9
Britain was also able utilise the resources of the private sector:
Public and private organisations gave Britain more strength in communications than any other country, though competition rose from 1900. The Admiralty and the GPO ranked among the greatest organisations handling electronic communications equipment in the world, with significant capabilities in research and development and links to private scientific and technological experts. Cable firms and the state worked symbiotically, on even terms of trade. Each levered the other against third parties. Firms dealt with all states; but the regulatory and strategic regime of the British empire offered profit and protection. Britain supported the interests of such firms through politics, at small financial cost. By nature, more than design, their cables linked the empire and made it the centre of world communication, with the lines of and to other states often becoming offshoots of imperial links. When Britain needed new cables laid during strategic crises, firms obliged and profited. At a small cost to taxpayers, firms laid the Pacific cable completing the 'all-Red route' - a telegraph system across the world that touched no foreign territory, making British communications uniquely invulnerable to interception among the powers. The Eastern Telegraph Company helped authorities to plan and enact cable censorship. Through the power of these submarine cables and the ability to cut foreign ones, Britain gained much at little cost in 1914.10
So by the time that more serious steps were taken to build up SIGINT capabilities between 1898 and 1914, Britain owned most of the world's telegraph cables.11 And this would prove advantageous for the British when its SIGINT capabilities were first put to the test in South Africa during the Second Boer War (1899-1902). The lead up to this conflict was as follows:
"In 1652 the Dutch East India Company founded a shipping station at the Cape of Good Hope [in South Africa].”12 The settlers consisted of Dutch Calvinists, German Protestants and French Huguenot refugees. Such settlers were known for their "dissent and a legacy of resentment against Europe" (calling themselves 'Afrikaners' or 'Afrikanders') and the "poorest and most independent of them were the trekboers (alias Boers), the wandering farmers whose search for new grazing lands brought them progressively deeper into African territory."13
Britain took possession of the colony during the Napoleonic Wars, given the importance of the Cape as a naval base on-route to India and the East. The Boers were against British rule, including its abolition of slavery in 1834, which the Boers relied on to maintain their farms. This led to the Great Trek between 1835-1837, which was the exodus "of about 5,000 Boers (with about 5,000 [slaves]) across the Orange and Vaal rivers beyond the north-east frontiers of the colony."14
In 1843, "Britain created a second colony by annexing Natal, one of the areas in which the [Boers] had concentrated" after the Great Trek.15 But the Boers there then traveled further north to establish two new republics: the Transvaal (1852) and the Orange Free State (1854). Though Britain recognised both republics, it attempted to annex Transvaal in 1877, starting the First Boer War which Britain lost. Independence was restored for the Transvaal "subject to conditions, including British supervision of its foreign policy."16
In 1870, a diamond-rush started in Kimberley "on the borders of Cape Colony."17 This was followed by a gold-rush in 1886 in Witwatersand, the Transvaal. Gold made the Transvaal "the richest and militarily the most powerful nation in southern Africa."18 But the discovery of these minerals also prompted a lot of immigration into the region. This included the entry of Uitlanders, which were mainly British immigrants who "swept along in the gold-rush."19 The population of Uitlanders was set to overtake that of the Boers in the Transvaal, leading to conflicts between the two. This included the Boers depriving the Uitlanders political rights. The control of the gold mines were also central to the tensions. Negotiations on these issues took place in June 1899, but eventually failed. Then on 9 October of that year, Paul Kruger (the President of the Transvaal) issued an ultimatum: the British must withdraw their troops from the borders of the Transvaal and the Orange Free State, or both republics would declare war. Britain rejected this ultimatum, triggering the Second Boer War.
During the war, the Boers had "a sophisticated telegraph and heliograph network and a Vigenere substitution cipher system which was identical to the most complex of the British ones used in the field."20 This led to the deployment by the British of codebreakers engaged in SIGINT against the Boers.
However, setting up the necessary systems for intercepting Boer communications took some time, since there were a general lack of preparations for the war. For example, "it took considerable time to put in place language specialists to cover all languages and to develop the expertise necessary to detect hidden code and cipher messages embedded in some of the code traffic."21 So despite the War Office apparently recognising the potential value of intelligence obtained from intercepted communications, Britain was not completely ready to use such techniques when war eventually came.
Moreover, Britain's efforts to thwart SIGINT operations by the Boers were not particularly effective. British war commanders sent important messages by telegraph cables unprotected, which the Boers were able to easily intercept. However, in recognising this danger, the British intelligence authorities sent "false orders by cable in plain language so as to confuse their enemies, not to mention their friends."22 Even so, "since British field ciphers were primitive and written keywords were sometimes captured, enciphered British traffic was potentially vulnerable, although there is no reason to suppose that the enemy ever exploited this opportunity."23
Accordingly, Britain's early work on SIGINT was somewhat weak. Though when SIGINT operations against the Boers were finally underway, British forces were able to gain "some useful intelligence from intercepted enemy telegrams."24 As Ferris notes:
The Boer field ciphers were insecure and Britain did know them during at least the later stages of the war. By October 1901 the Boer chief of field telegraphs warned that 'no doubt all codes are now known to the enemy'. His revised system certainly was captured by 1 January 1902 and distributed to all British columns by George Milne, a senior intelligence officer.25
Britain was able to break "the system used by Boer commanders in South Africa and their leaders in Europe."26 Authorities also managed to intercept "letters to and from businessmen thought to be working with the Boers."27
Interestingly though, there is little evidence to suggest that SIGINT gave Britain a meaningful advantage during the war. This is because such activity was "secret and uncoordinated and affected only the short period of conventional action, not the prolonged guerrilla phase of the war, and no British authority fully understood what had been done."28 Even during the negotiations to bring an end to the conflict, the intelligence gathered by intercepting Boer communications did not provide the British with information it was not already privy to:
By June 1901 the British and Boer commanders, Lord Kitchener and Louis Botha, were discussing secretly the possibility of a negotiated peace. In order to further this possibility, Kitchener allowed Botha to send an encoded telegram outlining the position to President Kruger of the South African Republic in his European exile. Seven weeks later Kitchener's aide de camp, Francis Maxwell, noted that the 'War Office have managed to decipher Bothas wire to Kruger and latters reply' (sic). However, this had provided 'nothing very much we didn't know', since captured documents had earlier revealed the gist of these messages. This episode is well known but poorly understood. B.A.H. Parritt, Thomas G. Fergusson and one of Kitchener's staff officers, William Birdwood, have claimed that these solutions gave Kitchener 'timely and highly valuable information on prospects for peace negotiations' or showed that, unlike Kruger, many Boer commanders 'regarded their position as hopeless and wanted peace'. In fact, Kitchener allowed these messages to be transmitted precisely because those prospects were already clear. While obviously useful, these solutions had in essence confirmed reliable information already received from other sources. According to a member of the intelligence department, George Cockerill, however, during the negotiations preceeding the treaty of Vereeniging, Britain broke further Boer messages between South Africa and Europe which in some unspecified fashion 'revealed to Lord Kitchener the true state of affairs'. If this statement is correct, codebreaking may have bolstered Kitchener's bargaining position during the final stage of negotiations.29
Nevertheless, Britain's experience with SIGINT during the Boer war formed part of a strategy that continued to develop over the decades that followed:
Both in the matter of the interception of enemy communications and of clandestine operations against enemy lines of supply, clear lessons were provided by events of the South African War which were held to make it imperative that adequate preparations for censorship and secret service activities needed to be put in place in peacetime long before war actually broke out, because the structure and networks essential to their effective functioning could not be improvised over night after war had broken out and the enemy had had time to bring his own defensive structure into effect.30
In developing these policies and protocols around SIGINT, some overgeneralisations were made. In particular, Britain did not anticipate how overwhelmed intelligence authorities would be if they sought to collect every message from the enemy. During the Boer conflict, it was easy to control traffic and identify appropriate targets. But in the context of a war involving many more nations with all the traffic that this would produce, attempting to intercept and read every communication would be much more difficult:
Not until overwhelmed by data could planners understand the problems of 'bulk processing' and their solutions. They misunderstood how much traffic censors must handle and how many people the task would require. Planners underrated the problem of analysis, assuming that the meaning of messages would be transparent. The War Office simply told censors that 'a careful examination of all messages passing over the wires will enable the censorship staff to collect much valuable information', which should be sent to authorities. The Admiralty...had similar views....When war began, censors were overwhelmed by traffic.31
Ultimately, the Boer war provided a skeleton for future British SIGINT. Britain would go on to develop its SIGINT policy and strategy:
The War Office maintained a rudimentary capacity to attack military and diplomatic codes in war. Its war plans assigned several officers to attack codes, part time, among other duties, and assumed that other officers would do so independently. The War Office published a Manual of Cryptography...which provided useful information for beginners. Officers practised codebreaking, which was studied at intelligence courses...The Royal Navy...fumbled towards signals intelligence without quite reaching it. From the moment that warships mounted wireless, post 1900, all Royal Navy fleet manoeuvres featured Sigint...In 1906, the Indian Army created a codebreaking agency of two officers...which broke Russian military and consular cyphers and the diplomatic traffic of Persia and China, its material widely circulated in the Indian and British governments. This agency prepared a memorandum showing officers how to break Russian military cyphers in case of war.
Britain also outstripped other powers in processing information for operational and strategic decision-making in command, control, communications, intelligence, reconnaissance and surveillance systems. These systems shaped the evolution of British intelligence during the First World War.32
WWI
After the Second Boer, Britain did not immediately establish "a permanent codebreaking bureau, despite the recognised fact that such an agency was needed to produce sustained cryptanalytical success."33 But Britain did become "increasingly interested in signals intelligence" after the Boer war.34
In 1909, a joint initiative between the War Office and the Admiralty resulted in the founding of the Secret Service Bureau. It had a domestic branch responsible for counter-espionage called MO5(g), which would later become to be known as the security service, or MI5. It also had a foreign branch called MI1(c), which later became to be known as MI6.35
The creation of MI5 and MI6 was fuelled by the concerns around the Imperial German government at the time and the strengthening of its maritime capabilities, which required a need to control secret intelligence operations both in the UK and abroad. However, the background to the establishment of the Secret Service Bureau is also riddled with paranoia among the British public about the proliferation of German spies on the island. Much of this was perpetuated by novels published in the early 1900s focused on the 'German Menace' and "supposedly based on the patriotic leaking of government secrets."36 For example, in 1903, Eskine Childers published The Riddle of the Sands, the plot of which contemplated "a German plot to invade England with a flotilla of barges."37 The public frenzy it caused forced the Royal Navy to investigate the matter, eventually concluding that such a secret invasion was impossible. But William Lee Queux's Invasion of 1910, published in 1906 and which was sold in the millions, explored the prospect of thousands of German operatives working undercover in Britain. This caused an even bigger public frenzy and certain British politicians "who wanted to expand Britain's relatively small peacetime army jumped on the bandwagon."38 This eventually pressured a rather dovish prime minister, Herbert Henry Asquith, into sanctioning the creation of the Secret Service Bureau:
This top-secret division - very few people knew about the bureau's existence - fundamentally altered the landscape of British intelligence forever. British espionage was nothing new, but its formalisation and growing proximity to Downing Street marked the beginning of a more organised and centralised intelligence system. It was not yet, though, an intelligence community linked to Downing Street, and early prime ministers remained unable or unwilling to engage with the secret world particularly closely.39
Along with the creation of the Secret Service Bureau came the passing of the Official Secrets Act 1911 (encouraged by MI5), which "allowed for much wider mail interception."40 Such legislation was enacted at a time when Britain was constrained by "a legal inability to intercept traffic [which] crippled the possibility of diplomatic codebreaking."41
...the United Kingdom had not right in peacetime to acquire telegrams from cable companies under general warrant. Nor could Whitehall acquire such power, even assuming that it had wished to do so, without risking a revulsion of public opinion. Even in 1919 British intelligence chiefs feared that the public would oppose such power and yet recognised that regular and legal access to cables was a necessary condition for diplomatic cryptanalysis in peacetime. Consequently, before 1914 those British officials who wished to wound were unable to strike, except at carrier pigeons.42
The creation of MI5 and MI6 and the legal changes also coincided with the advent of radio, another factor increasing the importance of SIGINT:
The scope for signals intelligence began to increase after 1896. The gradual rise of a new form of military communication, radio, made possible a marriage between the hitherto separate components of modern signals intelligence - interception and codebreaking. Since all radio traffic could be intercepted, codebreakers would have a steady flow of messages to attack and a greater chance to solve them.43
The emergence of radio was important. Prior to this, and as was the case during the Second Boer War, telegraphy "did not offer great room for the practice of [SIGINT]", and so such form of intelligence gathering was limited:
Although one could secretly acquire the cryptographic systems of foreign armies and navies and train one's personnel in peace to intercept and solve the military traffic of potential enemies in war, there had been little incentive to do so. During the telegraph age, no power could easily intercept an enemy's military traffic in peacetime. One could merely exploit fleeting opportunities to observe the signals of, say foreign warships encountered at sea.44
But despite the adoption and development of radio by the military, and the creation of the Secret Service Bureau comprising of MI5 and MI6, Britain made only gradual progress on the two major components of SIGINT: interception and codebreaking.
The British Navy initially made faster progress on the interception of radio communications than the army:
In [1904]...British warships were instructed to transmit to the Admiralty copies of all foreign radio messages which they intercepted. Two years later the NID published preliminary assessments of the radio procedure of foreign navies, based mostly on open sources. This report referred, however, to intercepted messages of the French American and Japanese navies. Only around 1908-10, however, could the Royal Navy frequently intercept the messages of its anticipated enemy, the German navy.45
Conversely, the British army was initially more advanced on codebreaking:
An intellectual gulf stood between the recognition that messages could be intercepted and that these might be solved. Where the army lagged in appreciating the first possibility, it outpaced the navy in the latter. Thus, the services reached an even level in the new world of signals intelligence. Army officers had a greater interest in and understanding of codebreaking than their naval counterparts...the army's interest in cryptanalysis rose precisely at the time that its radio service first began to function with any degree of efficiency.46
During this time prior to WWI, Britain still lacked an agency dedicated to SIGINT operations. The army and the navy continued developing their respective strengths in this area, but the skills of both remained somewhat separate.47 As Ferris explains:
The British fighting services did not establish cryptanalytical agencies before August 1914 because each lacked half the means to begin military codebreaking: the ability to intercept messages and to solve them. The army's radio units could scarcely transmit British messages, let alone intercept foreign ones. Although the War Office knew the system of the field cipher of the German army, it could not intercept the latter's radio traffic; conversely, the Royal Navy could intercept German naval messages but had no knowledge of its codes or of codebreaking.48
Nevertheless, the British still managed to identify the value of SIGINT in wartime and therefore made efforts to ensure its development and the merging of its interception and codebreaking capabilities:
In the two years before August 1914 the services seem to have been breaking free from their Victorian attitudes toward signals intelligence and to have realised that in time of war enough radio messages might be intercepted to render possible the solution of enemy codes and ciphers. Consequently, they took novel steps in peacetime such as studying or seeking to acquire the crytographic systems of potential enemies and training some personnel in cryptanalytical techniques. Before August 1914 they intended to establish codebreaking agencies whensoever any major war should occur.49
So in the build up to WWI, Britain was not completely naive to the importance of SIGINT. Rather, it was gradually preparing itself for the next opportunity to deploy its SIGINT operations against its enemies during war. And WWI would end up being this very opportunity:
Around 1900, intelligence passed a tipping point, awaiting only a trigger. This revolution stemmed from the fusion of several developments: in sources and signals systems, including some which had unprecedented reliability and real-time nature; in modes of collection, assessment and dissemination, and the integration of intelligence into planning and action; and in forms of command, control, communications and intelligence, which unified all the domains of power and tactical, operational and strategic spheres.
That trigger sprang in 1914. When it did, British admirals, diplomats, generals and statesmen and some experience with and expectations for Sigint. Rather than being a radical break with the past, the establishment of codebreaking bureaus in 1914 was the logical culmination of a long-standing trend. When war began, British authorities treated Sigint with enthusiasm, rather than embarrassment or ignorance.50
Accordingly, "the outbreak of the Great War was the occasion rather than the cause for the creation of British codebreaking agencies."51 This was when SIGINT really matured and "the modern age of intelligence began."52 This encompassed the expansion of the already-established intelligence agencies:
The First World War triggered Britain's tangible intelligence changes. MI5 had only fifteen staff prior to the conflict, but it soon expanded. The Post Office also assumed an intelligence function. It grew into a Censor's Office that employed over 2,000 officials, each steaming, scanning and resealing some 150 letters per day. Britain now boasted a serious domestic surveillance apparatus. By the last year of the war, censorship employed 4,871 people, a sizeable engine of surveillance. In the empire, MI5 worked closely with security agencies in Delhi to thwart German plots to promote revolts amongst imperial subjects.53
The Committee of Imperial Defence, an ad hoc group within the British government set up just after the Second Boer War and responsible for military strategy, made an important decision at the start of WWI; German-owned under sea cables should be destroyed. And so on 5 August 1914, around a week after the war began, a cable ship called Alert cut German cables running down the English Channel. This forced the Germans to send communications using cables belonging to other countries or via wireless means, in particular radio.
Interception sites were built along the east coast of England to intercept German naval communications. In addition, "radio stations of the Royal Navy, the post office, and the Marconi company began to pick up coded messages, apparently of German origin."54 These coded messages were then passed on to the Admiralty's Intelligence Division.
However, at first the Intelligence Division, whilst recognising the potential intelligence such coded messages could reveal, lacked the ability to break the codes to read the messages. Accordingly, Rear Admiral Henry Oliver, who was head of the division, turned to his friend Sir Alfred Ewing, the Director of Naval Education. Ewing was previously a engineering professor and had experience with radio communications and ciphers. Ewing's involvement sparked the beginnings of the British intelligence agency responsible for the intercept and deciphering of perhaps the most crucial German communication sent during the war:
Oliver told Ewing he had no one to deal with the intercepts; would Ewing see if he could making anything of them? Grasping "at even the most unpromising chance of being useful," Ewing accepted at once.
[...]
To assist him, he called on some people whose abilities would be useful and who were discreet and available: faculty members, particularly instructors in German, at the Royal Navy Colleges at Dartmouth and Osborne, which were on vacation in August.
[They] worked in Ewing's cramped office. They did little more than sort and file intercepts, learn to distinguish German naval messages from military ones, and discover that call signs such as POZ and KAY, the "names" of radio stations, were not the same as the coded texts of messages.55
But Ewing's group struggled to break the codes. This was because they were missing a crucial part of the codebreaking process, the codebooks. These were crucial for Room 40’s codebreaking efforts during WWI because they contained the structured systems that the German military and navy used to encode their messages. This made the codes more complex and therefore lacked any kind of recognisable pattern. So without such codebooks, deciphering the intercepted German messages would have been significantly more difficult, if not impossible:
In autumn 1914, the Australian and Russian navies captured copies of the Germany navy's main signals books - the Signalbuch der Kaiserlichen Marine (SKM) and the Handelsverkehrsbuch (HVB), used by warships, Zeppelins and U-boats - and gave them to Britain. A British fishing boat soon recovered a safe, thrown from a sinking Germany destroyer, that held a copy of the Verkehrsbuch, which the Germany navy used to communicate with naval attachés and warships abroad...Though German authorities quickly concluded that their SKM and HVB signals books might have been compromised, still they used them for several years.56
When Ewing's team got their hands on these codebooks, their codebreaking began to significantly improve. So "before the war was four months old, Britain had gained, mainly through means other than codebreaking, the ability to read the most secret intentions of its chief enemy's navy."57 As a result, the team expanded and a bigger workplace had to be found. In November 1914, one was found in Room 40 of the Old Building of the Admiralty. And this is how Room 40, the infamous WWI British intelligence agency, got its name.58 Reginald 'Blinker' Hall would become its director.
The War Office had also set up its own codebreaking unit during the war called MI1b, which was based in London. Although it initially cooperated with Room 40, "differences developed in both personality and approach, rendering any harmony short-lived."59 Even so, both agencies managed to "break German, French and American codes, alongside a host of other streams of high-level communications."60
Throughout much of WWI, SIGINT was very important to Britain, intercepting "70 million cables, 20 million wireless messages, and a billion seamail letters of foreigners, which guided economic warfare."61 It was the dominant source of intelligence for the Royal Navy and from August to November 1914, "the combination of [SIGINT] and aerial reconnaissance proved more valuable for the British Army than every other sources put together."62 Even during the trench warfare, SIGINT remained somewhat valuable:
...between 1915 and 1917, the Western front was characterised by dense force-to-space ratios, elaborate defensive systems, and firepower which could kill but not move. Breakthrough was extremely difficult to achieve; exploitation impossible. Both side also possessed intelligence services of high skill, which simultaneously penetrated the other's intentions and capabilities. Intelligence cancelled out much of its own effect: but not all of it. In this campaign of attrition, intelligence presided over a realm of small advantages which collectively had great impact. It affected thousands of small actions and scores of great ones, increasing one's chance for victory, and reducing its cost, for both sides at once.63
Room 40 played an important role during Britain's naval engagements during the war, including its detection of German sorties prior to the Battle of Dogger Bank in 1915 and the Battle of Jutland in 1916. But Room 40's most important contribution in WWI was its interception and decoding of the infamous Zimmermann telegram.
In January 1917, the Germans planned to carry out unrestricted submarine warfare in the North Atlantic. In doing so, it was predicted that they would encounter and be able to sink American merchant vessels, bringing the United States into the war. Accordingly, Arthur Zimmermann, the German foreign minister, decided to dispatch a telegram to the German ambassador in Mexico, Heinrich von Eckardt. In the telegram, Zimmermann instructed von Eckardt to propose a military alliance with Mexico. The exact message was as follows:
On February 1 we intend to begin submarine warfare without restriction. In spite of this it is our intention to endeavour to keep the United States neutral. If this attempt is not successful, we propose an alliance on the following basis with Mexico:
That we shall make war together and together make peace; we shall give general financial support, and it is understood that Mexico is to reconquer her lost territory of New Mexico, Texas and Arizona. The details are left to you for settlement.
You are instructed to inform the President of Mexico of the above in the greatest confidence as soon as it is certain that there will be an outbreak of war with the United States, and suggest that the President of Mexico shall on his own initiative communicate with Japan suggesting the latter's adherence at once to this plan, and at the same time offer to mediate between Germany and Japan.
Please call to the attention of the President of Mexico that the employment of ruthless submarine warfare now promises to compel England to make peace in a few month [sic]. – Zimmerman.
(The signature dropped the second n of the name Zimmermann for telegraphic purposes.)
Zimmermann's message was intended to be taken on a German submarine. However, "the vessel broke down before leaving port, forcing Berlin to trust the safety of its ciphers."64 The telegram was believed to be intercepted at one of the ports in Cornwall as it was conveyed through the British telegraphic network. The intercepted message was passed on to Room 40 where Nigel de Grey, one of the most talented codebreakers in the team, managed to partially decrypt it within hours. Both he and William Montgomery completed the decryption of the message with the help of a recovered codebook that was abandoned by Wilhelm Wassmuss during a failed German expedition to Afghanistan. By February, de Grey and Montgomery managed to decrypt the message, revealing Germany's plans in the North Atlantic and its proposal to Mexico.65
At first, Hall, Room 40's director, was reluctant to share the intelligence with the Americans as it would reveal the work his team was doing in deciphering coded messages, including those from US diplomatic traffic. During his stalling, Germany would announce the resumption of "unrestricted" submarine warfare, severing its diplomatic ties with the US. The message was eventually passed on to the American delegation in London in late-February and then eventually to Washington, with the British being aware that its revelation could very well bring the US into the war. And indeed, in April 2017, due to the Zimmermann telegram and other factors (including the German sinking of three merchant US vessels), American opinion on entering the war unified and the US Senate declared war on Germany.66
The Zimmermann telegram was Room 40's greatest achievement during the war:
British codebreakers delivered the greatest intelligence coup of the First World War. They had intercepted what would become famous as the 'Zimmermann telegram'.
[...]
The Zimmermann telegram is a rare example of a single piece of intelligence changing the course of history. The way in which the British exposed it was elegant, but had nothing to do with Downing Street. Instead, it was a cooperative venture between Room 40 and the Foreign Office - and perhaps for that reason it was not bungled...President Woodrow Wilson had won his recent election campaign on the slogan 'He kept is out of war'. But, provoked by the declared war on Germany in April 2017.67
While the Second Boer War gave a limited glimpse into how SIGINT could contribute to warfare, WWI proved exactly how crucial a more matured version of such operations could be for Britain:
Britain won the [SIGINT] struggle against Germany and its victories were significant. Material mastery in sea power was reinforced, so producing the easiest great war the Royal Navy has ever faced, and making the application of blockade even more effective and less traumatic than usual; [SIGINT] helped Britain evade grave dangers with the United States and instead gain American aid for free. Only on the Western front were British and German signals intelligence equal in quality. Britain led the world in [SIGINT] which, alongside financial support, was an unsung contribution to Allied power.68
Concluding remarks
British SIGINT had steady beginnings between 1850 and 1918. During the Second Boer War such operations were limited and its true value was yet to be determined. That determination was made during WWI, when SIGINT really proved its worth. This was the point at which British SIGINT become a crucial part of military strategy and national security. And it was also at this point that the intelligence community started to expand and cement itself, later becoming a crucial part of the next world war.
The importance of British SIGINT in WWI can easily be overlooked. Despite being much more advanced and better organised than during the Second Boer War, some aspects were still lacking. For example, the collaboration between the ad hoc intelligence agencies created by the Admiralty (Room 40) and the War Office (MI1b) was weak and could have easily been more problematic with both remaining in their silos, resulting in the stifling of Britain's progress on intercepting and decrypting coded communications. But there are many parts of this period of British SIGINT that were key: the utilisation of cable networks and the private sector, the establishment of MI5 and MI6, the advancements in both interception and codebreaking, and the importance of capturing codebooks to enable the deciphering of encrypted messages.
From a legal and policy perspective, legislation around SIGINT was essentially non-existent, and the laws that were relevant did more to expand powers than constrain them, including the Official Secrets Act. This could be understandable, or at least predictable, given how SIGINT's development accelerated in the context of war, during which the appetite for constraining state power may not be large. It is also interesting to note how public opinion managed to influence policy developments around state surveillance; the 'German Menace' novels published prior to WWI managed to cajole a reluctant prime minister into expanding surveillance powers and creating government agencies dedicated specifically to intelligence gathering both at home and abroad. Indeed, it would not be until after WWII that the legal framework around state surveillance would really evolve.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.30.
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023), p.28.
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023), p.32.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 434.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 433.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 434.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 435.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 435.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.21.
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 435.
Thomas Pakenham, The Boer War (Random House 1979), p.xiii.
Thomas Pakenham, The Boer War (Random House 1979), p.xiii.
Thomas Pakenham, The Boer War (Random House 1979), p.xiii.
Thomas Pakenham, The Boer War (Random House 1979), p.xiii.
Thomas Pakenham, The Boer War (Random House 1979), p.xiv.
Thomas Pakenham, The Boer War (Random House 1979), p.xiv.
Thomas Pakenham, The Boer War (Random House 1979), p.xiv.
Thomas Pakenham, The Boer War (Random House 1979), p.xiv.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 435.
Chapman, ‘British Use of ‘Dirty Tricks’ in External Policy Prior to 1914’, War in History (2002), 70.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 435.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 435-436.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 436.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 437.
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 436.
Chapman, ‘British Use of ‘Dirty Tricks’ in External Policy Prior to 1914’, War in History (2002), 77.
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 437.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 443.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.26.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.23.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.23.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.24.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), pp.25-26.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.26.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 446.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 446.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 448.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 446.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 450.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 450.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.30.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 451.
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 451.
'The Edwardian Roots of British Sigint' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Ferris, ‘Before ‘room 40’: The British Empire and signals intelligence, 1898–1914’ Journal of Strategic Studies (1989), 442.
'Britain and the Birth of Signals Intelligence, 1914 to 1918' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.30.
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023), p.25.
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023), pp.25-26.
'Britain and the Birth of Signals Intelligence, 1914 to 1918' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023), p.28.
David Khan, Seizing the Enigma: The Race to Break the German U-Boat Codes, 1939-1943 (Frontline Books 2023), p.27.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.29.
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.29.
‘Introduction’ in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
'Britain and the Birth of Signals Intelligence, 1914 to 1918' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
'Britain and the Birth of Signals Intelligence, 1914 to 1918' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.36.
'Britain and the Birth of Signals Intelligence, 1914 to 1918' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).
Richard J. Aldrich and Rory Cormac, The Black Door: Spies, Secret Intelligence and British Ministers (William Collins 2016), p.36.
'Britain and the Birth of Signals Intelligence, 1914 to 1918' in John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain’s Secret Cyber-Intelligence Agency (Bloomsbury 2020).