Admiralty Building, London

First World War technology: Room 40 secret intelligence unit

In the lead-up to the outbreak of hostilities in August 1914, Britain recognised the role telegraphy and wireless would play in the conflict, and took steps to stay ahead in the communications war. In advance of next month's First World War centenary issue, we plot the birth of the secret intelligence unit, 'Room 40'.

According to legend, in the run-up to the First World War the head of the Royal Navy's intelligence department, Admiral Henry Oliver, was the recipient of a few intercepts of German wireless signals. They had been sent to the Admiralty by wealthy amateur radio enthusiasts who had plucked them out of the air – the dunderheads at the Admiralty not having thought of using any of their wireless sets to listen-in to the future enemy.

As the intercepts piled up on his desk, Oliver wondered what to do with them. In the first few days of the war he had a lunch appointment with an old friend, engineer and physicist Sir James Alfred Ewing (1855-1935) – known as Alfred Ewing, an academic engineer who was then head of the Navy's education department. Oliver took the intercepts with him to the lunch, and handed them to Ewing, asking him to see if anything useful could be done with them.

Ewing returned to his office, summoned a couple of German language teachers from the Navy's training schools, and soon set-up what later became known as Room 40, the Navy's initial interception and code-breaking operation. The modern era of technology-fed intelligence gathering in support of military operations had begun.

Despite this unplanned start to life, Room 40 went on to have great success in reading German naval and diplomatic messages. Thanks to the interception of a diplomatic telegram in 1917, which revealed that Germany was encouraging Mexico to attack the USA, America entered the war and eventually swung the balance of force in favour of the Allies. Oliver's chance hunch that Ewing might make something out of the incomprehensible German intercepts proved to be vital to the outcome of the war.

In fact the Oliver/Ewing lunch story was a suitable cover put about after the end of the war to create the impression that British code-breaking activities were in the main down to good old-fashioned luck, and were unlikely to be repeated in any later conflict. The truth, however, is quite different.

In the lead-up to the First World War there were two main modern communications technologies of strategic interest to the armies and navies of the European major powers: the telegraph and the wireless.

Wireless was relatively new, having been invented only at the turn of the century; but the telegraph was well-established – and the international telegraph cable network was predominantly owned and operated by British companies.

The British communications network was consciously dubbed the 'All-Red Network' or 'All-Red Line' because it linked the far-flung outposts of the British Empire, then marked in red on most maps. In the Imperial capital London the Committee for Imperial Defence (CID), effectively the British strategic planning authority, had long had the role of communications networks in the event of war under its consideration.

The All-Red Network started life as ad hoc links created by commercial interests; but the telegraph became so important to the administration and defence of the Empire that the British state took an active interest, financing links to disparate distant colonies and dominions that offered insufficient telegraphic traffic to justify a commercial venture. The CID ensured that it was constructed with alternative 'redundant' routes, so that the cutting of any one cable would not interrupt communications. By the beginning of the 20th Century the British telegraph network circled the globe.

The British domination of the world telegraph network was not appreciated by other powers, especially Germany and the US. Both these nations operated alternative, non-British cable links across the Atlantic, but such bypassing had little effect on British control of communications with the rest of the world.

Cables in conflict

From this starting point the CID planned an offensive communications war that would be unleashed as soon as any major armed conflict between Britain and Germany was confirmed. The German transatlantic cables and telegraph links with other countries that ran under the seas and oceans would be severed by specially-equipped British ships in the first few days of any such war.

Germany's communications outside Eurasia would thereby be severely constrained, and thus its ability to wage war limited to a greater or lesser degree. Its propaganda campaigns in the US (where, it should be remembered, the German community was substantial) would be made difficult, if not impossible.

Germany's ability to work in concert with sympathetic but distant powers, such as Spain or Sweden, would be severely impeded. Its potential for conducting military action in German colonies in Africa and Asia would be stifled or localised.

Germany would still rely on the resources of the Eurasian continent, though Britain's command of most of the world's telegraphic communications could summon the support of its far-flung colonies and dominions, and it would retain its ability to continue to trade with countries outside the Empire's embrace. In 1914 modern war was as much a struggle between nations to rally support for their industrial strength as it was a clash of military forces. This was a very modern strategy that understood the role of communications technology and its role in war, and was planned in the decade before the war; it was certainly not down to amateurish luck.

Marconi: Britain's Italian ally

Britain was also in the lead in that other vital strategic communications technology – wireless telegraphy. Wireless was set to transform the 'Victorian Internet' of landline telegraphy into what we could call the 'Edwardian Internet', having been developed as a practical technology at the turn of the century by the Italian-British Guglielmo Marconi.

Wireless telegraphy had already proved itself an influential technology in the years before 1914 through its role in events such as the Titanic tragedy. With respect to military deployment, Marconi first offered his wireless to the Italian Navy, but fortunately for the British it turned him down. He approached the Royal Navy and, after some initial reluctance, his work was welcomed.

The Royal Navy helped Marconi develop his equipment and test it at sea on its ships. This gave him the inestimable advantage of trialling his wireless transmitters and receivers under real-life conditions, improving his apparatus by repeated trial and error.

The German Imperial Navy, on the other hand, was less welcoming to suggestions from a German inventor to develop a competing wireless technology. Admiral Tirpitz insisted that the German navy should only adopt wireless once it was a fully- developed and properly-functioning system. This gave the British a number of advantages.

First code-breaking machines?

The setting up of Room 40 was no mere piece of fruitful good fortune. The Navy had already planned its formation at the start of any war, and engineer and physicist Sir Alfred Ewing had already been identified as the best man to lead it.

Ewing had some experience in submarine cable technology, plus an interest in codes and ciphers. He had even been involved in work for the CID on some manner of 'cipher machine' unfortunately, we know nothing about this device except that it proved 'futile'. Another British telecomms engineer, working for the Marconi Company, invented a cipher device, but very little information about it is known.

All the same, these rare mentions of cipher machines in the archives guided an important part of what Room 40 did later in the war with code-breaking machinery. This led eventually, in the Second World War, to the invention of Colossus, the electronic code-breaking machine used at Bletchley Park, and usually cited as the first electronic computer – more about this next month.

Less well-known than Room 40 is the British army's code-breaking unit, also set up on the outbreak of war, but again planned in advance. For various reasons the army unit, eventually known as MI1(b), has remained in the shadows, and much about its various wartime operations remains hidden – but there is sufficient archival material to establish that both the navy and army code-breaking units were pre-planned by the strategic thinking of the CID.

The information available in the archives is limited, but it seems that the crucial year for decision making about these matters was 1904, a good decade before hostilities with Germany finally came into being. An army interception unit was set up at Simla in northern India to monitor Russian communications on the 'north-west frontier'.

The Royal Navy's warships were first ordered to undertake systematic interception of foreign wireless signals. Most perspicaciously, perhaps, some effort was also devoted to obtaining copies of international telegraph messages sent via the British telegraph cables.

Britain declares war...

In August 1914 the British government declared war with Germany. It is being frequently reported during the present commemorations of the war 100 years on from its outbreak, that the British casus belli was the German invasion of neutral Belgium. In fact, the government's decision was arguably informed by concern over the threat posed to Britain's seaborne Empire if the German military were to gain control of the Channel ports.

When the war started, the navy duly cut German telegraph cables. The cable-repair ship SS Telconia used its grappling hooks to lift each cable in shallow water near the shore, and cut out a short length. A few months later British ships returned and helped patch the cables into the British cable network.

The navy also attacked and closed down Germany's colonial wireless stations and, over the next few months, endeavoured to chase German ships out of the world's oceans, forcing the great Imperial Navy to take cover in its home ports, daring only the odd venture out into the North Sea.

Room 40 also gained the inestimable advantage of acquiring copies – thanks to the Russians, Australians, and one still-secret source – of the three main German naval codebooks. This, once the code-breakers worked out how to crack the ciphers applied to the codes, allowed the experts of Room 40 to read all those wireless signals picked up from the Imperial Navy, which was prolific in its use of the air waves – even in its home ports where security assurance for confidential communiques could have been ensured with the use of cables.

Room 40's success in acquiring intercept intelligence may not initially have been matched by successful use of the intelligence by the Admiralty; but it did reinforce the ability of the Royal Navy to be at sea whenever the German Hochseeflotte (High Seas Fleet) ventured forth on its operations.

A submarine menace in the shape of the U-boat later posed serious threats until the Admiralty jettisoned its distaste for running convoys, but wireless interception meant that German naval strategy suffered comprehensive defeat within the first few months of the war.

On land, MI1(b) and its French counterpart used wireless intercept intelligence to halt German advance into Belgium and France at the First Battle of the Marne (September 1914) – one of the decisive battles of the war. The Allied military forces prevented the planned German knock-out blow aimed at France. Germany was thus forced into what it had tried to avoid – a war on two fronts, against France and Britain in the west, and Russia in the east.

From the outset of the conflict wireless intercepts had the effect of undermining Germany's strategy both on land and at sea, turning its plans for rapid, decisive victories into a draining war of attrition in which the key factor would not be simple military prowess, but economic adaptability and social cohesion. The CID's strategy of playing for the long war, blunting the attacks of German military forces and isolating the enemy, was initially proved successful. 

Paul Gannon is the author of 'Inside Room 40' (Ian Allen), and has here drawn upon new information that has become available since its publication in 2011.

In the next issue of E&T: were Room 40's attempts at building a code-cracking machine the first step to computerised intelligence processors like Colossus?

Further information

Recent articles

Info Message

Our sites use cookies to support some functionality, and to collect anonymous user data.

Learn more about IET cookies and how to control them

Close