Room 40
Encyclopedia
In the history of Cryptanalysis
, Room 40 (latterly NID25) was the section in the Admiralty
most identified with the British cryptoanalysis effort during the First World War
.
Room 40 was formed in October 1914, shortly after the start of the war. Admiral Oliver
, the Director of Naval Intelligence, gave intercepts from the German radio station at Nauen
, near Berlin
, to Director of Naval Education Alfred Ewing
, who constructed ciphers as a hobby. Ewing recruited civilians such as William Montgomery, a translator of theological works from German, and Nigel de Grey
, a publisher.
The basis of Room 40 operations evolved around a German naval codebook, the Signalbuch der Kaiserlichen Marine (SKM), and maps (containing coded squares), which had been passed on to the Admiralty by the Russians. The Russians had seized them from the German cruiser Magdeburg
when it ran aground off the Estonia
n coast on 26 August 1914. Two of the four copies that the warship had been carrying were recovered; one was retained by the Russians and the other passed to the British.
In October, 1914, the British also obtained the Imperial German Navy's Handelsschiffsverkehrsbuch (HVB), a codebook used by German naval warships, merchantmen, naval zeppelin
s and U-Boat
s. This had been captured from the German steamer Hobart by the Royal Australian Navy
on 11 October. On 30 November a British trawler recovered a safe from the sunken German destroyer S-119, in which was found the Verkehrsbuch (VB), the code used by the Germans to communicate with naval attachés, embassies and warships overseas.
In March, 1915, the luggage of Wilhelm Wassmuss
, a German agent in Persia, was captured and shipped, unopened, to London, where then-Director of Naval Intelligence Admiral Sir William Reginald Hall
discovered that it contained the German Diplomatic Code Book, Code No. 13040.
The function of the program was compromised by the Admiralty's insistence upon interpreting Room 40 information in its own way. Room 40 operators were permitted to decrypt, but not to interpret the information they acquired.
The section retained "Room 40" as its informal name even though it expanded during the war and moved into other offices. It has been estimated that Room 40 decrypted around 15,000 German communications, the section being provided with copies of all intercepted communications traffic, including wireless
and telegraph traffic. Until May 1917 it was directed by Alfred Ewing, and then direct control passed to Captain
(later Admiral) Reginald 'Blinker' Hall
, assisted by William Milbourne James
.
on cable communications concluded that in the event of war with Germany, German-owned submarine cables should be destroyed. On the night of 3 August, 1914, the cable ship Alert located and cut Germany's five trans-Atlantic cables, which ran down the English Channel
. Soon after, the six cables running between Britain and Germany were cut. As an immediate consequence, there was a significant increase in cable messages sent via cables belonging to other countries, and cables sent by wireless. These could now be intercepted, but codes and ciphers were naturally used to hide the meaning of the messages, and neither Britain nor Germany had any established organisations to decode and interpret the messages. At the start of the war, the navy had only one wireless station for intercepting messages, at Stockton. However, installations belonging to the post Office and the Marconi Company, as well as private individuals who had access to radio equipment, began recording messages from Germany.
Intercepted messages began to arrive at the Admiralty intelligence division, but no one knew what to do with them. Rear-Admiral Henry Oliver
had been appointed Director of the Intelligence division in 1913. In August, 1914, his department was fully occupied with the war and none had experience codebreaking. Instead he turned to a friend, Sir Alfred Ewing
, the Director of Naval Education (DNE), who previously had been a professor of engineering with a knowledge of radio communications and who he knew had an interest in ciphers. It was not felt that education would be a priority during the expected few months duration of the war, so Ewing was asked to set up a group for decoding messages. Ewing initially turned to staff of the naval colleges Osborne and Dartmouth who were currently available due both to the school holidays and to naval students having been sent on active duty. Alastair Denniston
had been teaching German but later became second in charge of Room 40, then becoming Chief of its successor after the First World War, the Government Code and Cypher School (located at Bletchley Park
during the Second World War). Others from the schools worked temporarily for Room 40 until the start of the new term at the end of September. These included Charles Godfrey, the Headmaster of Osborne (whose brother became head of naval Intelligence during the Second World War), two Naval instructors, Parish and Curtiss and scientist and mathematician Professor Henderson from Greenwich Naval College. Volunteers had to work at codebreaking alongside their normal duties, the whole organisation operating from Ewing's ordinary office where codebreakers had to hide in his secretary's room whenever there were visitors concerning the ordinary duties of the DNE. Two other early recruits included R. D. Norton who had worked for the Foreign Office, and Lord Herschell
, who was a linguist, an expert on Persia and an Oxford graduate. None of the recruits knew anything about codebreaking, but were chosen for a knowledge of German and a certainty they could keep the matter secret.
A similar organisation had begun in the Military intelligence department of the War Office
, which become known as MI1b, and Colonel Macdonagh proposed that the two organisations should work together. Little success was achieved except to organise a system for collecting and filing messages until the French obtained copies of German military ciphers. The two organisations operated in parallel, decoding messages concerning the Western Front
. A friend of Ewing's, a barrister by the name of Russell Clarke, plus a friend of his, Colonel Hippisley, approached Ewing to explain that they had been intercepting German messages. Ewing arranged for them to operate from the coastguard station at Hunstanton in Norfolk, where they were joined by another volunteer, Leslie Lambert (later becoming known as a BBC broadcaster under the name A. J. Alan). Hunstanton and Stockton formed the core of the interception service (known as 'Y' service), together with the post office and Marconi stations, which grew rapidly to the point it could intercept almost all official German messages. At the end of September, the volunteer schoolmasters returned to other duties except for Denniston, but without a means to decode German naval messages there was little specifically naval work to do.
. Two light cruisers, Magdeburg and Augsberg
and a group of destroyers all commanded by Rear-Admiral Behring were carrying out a reconnaissance of the Gulf of Finland when the ships became separated in fog. Magdeburg ran aground on the island of Odensholm off the coast of Russian controlled Estonia
. The ship could not be refloated so the crew was to be taken onboard by the destroyer SMS V26. The commander, Korvettenkapitän Habenicht prepared to blow up the ship after it had been evacuated, but the fog began to clear and two Russian cruisers Pallada and Bogatyr
approached and opened fire. The demolition charges were set off prematurely, causing injuries amongst the crew still on board, and before secret papers could be transferred to the destroyer or otherwise properly disposed of. Habenicht and fifty seven of his crew were captured by the Russians.
Exactly what happened to the papers is not clear. The ship carried more than one copy of the SKM codebook, and copy number 151 was passed to the British. The German account is that most of the secret papers were thrown overboard, but the British copy was undamaged and was reportedly found in the charthouse. The current key was also needed in order to use the codebook. A gridded chart of the Baltic, the ships log and war diaries were all also recovered. Copies numbered 145 and 974 of the SKM were retained by the Russians while was dispatched from Scapa Flow
to Alexandrovosk in order to collect the copy offered to the British. Although she arrived on 7 September, due to mixups she did not depart until 30 September and returned to Scapa with Captain Kredoff, Commander Smirnoff and the documents on 10 October. The books were formally handed over to the First Lord, Winston Churchill, on 13 October.
The SKM by itself was incomplete as a means of decoding messages since they were normally enciphered as well as coded, and those that could be understood were mostly weather reports. Fleet paymaster C. J. E. Rotter, a German expert from the naval intelligence division, was tasked with using the SKM codebook to interpret intercepted messages, most of which decoded as nonsense since initially it was not appreciated that they were also enciphered. An entry into solving the problem was found from a series of messages transmitted from the German Norddeich transmitter, which were all numbered sequentially and then re-enciphered. The cipher was broken, in fact broken twice as it was changed a few days after it was first solved, and a general procedure for interpreting the messages determined. Enciphering was by a simple table, substituting one letter with another throughout all the messages. Rotter started work in mid October but was kept apart from the other codebreakers until November after he had broken the cipher.
The intercepted messages were found to be intelligence reports on the whereabouts of allied ships. This was interesting, but not vital. Russel Clarke now observed that similar coded messages were being transmitted on short wave, but were not being intercepted because of shortages of receiving equipment, in particular the aerial. Hunstanton was directed to stop listening to the military signals it had been intercepting and instead monitor shortwave for a test period of one weekend. The result was information about the movements of the High seas fleet, and valuable naval intelligence. Hunstanton was now permanently switched to the naval signals and as a result stopped receiving messages valuable to the military. Navy men who had been helping the military were withdrawn to work on the naval messages, without explaining why because the new code was kept entirely secret; and the result was bad feeling between the naval and military interception services and a cessation of cooperation between them, which continued to 1917.
The SKM (sometimes abbreviated SB in German documents) was the code normally used during important actions by the German fleet. It was derived from the ordinary fleet signal books used by both British and German navies, which had thousands of predetermined instructions which could be represented by simple combinations of signal flags or lamp flashes for transmission between ships. There were 34,300 instructions each represented by a different group of three letters. A number of these reflected old-fashioned naval operations, and did not mention modern inventions such as aircraft. Ships were identified by a three letter grouping beginning with a Beta symbol. Messages not covered by the predetermined list could be spelled out using a substitution table for individual letters. The signals used four symbols not present in ordinary Morse code (given the names alpha beta gamma and rho), which caused some confusion until all those involved in interception learnt to recognise them and use a standardised way to write them.
The sheer size of the book was one reason it could not easily be changed and the code continued in use until summer 1916. Even then ships at first refused to use the new codebook because the replacement was too complicated, so the Flottenfunkspruchbuch (FFB) did not fully replace the SKB until May 1917. Doubts about the security of the SKB were initially raised by Behring, who reported that it was not definitely known whether Magdeburg's code books had been destroyed or not, and it was suggested at the court martial enquiry into the loss that books might anyway have been recovered by Russians from the clear shallow waters where the ship had grounded. Prince Henry of Prussia
, commander in chief of Baltic operations, wrote to the C-in-C of the HSF that in his view it was a certainty that secret charts had fallen into the hands of the Russians, and a probability that the codebook and key had also. The German navy relied upon the reenciphering process to ensure security, but the key used for this was not changed until 20 October and then not changed again for another three months. The actual substitution table used for enciphering was produced by a mechanical device with slides and compartments for the letters. Orders to change the key were sent out by wireless, and frequently confusion during the changeover period led to messages being sent out using the new cipher and then being repeated with the old. Key changes continued to occur infrequently, only 6 times during 1915 from March to the end of the year, but then more frequently from 1916.
There was no immediate capture of the FFB codebook to help the admiralty understand it, but instead a careful study was made of new and old messages, particularly from the Baltic, which allowed a new book to be reconstructed. Now that the system was understood, Room 40 reckoned to crack a new key within three to four days, and to have reproduced the majority of a new codebook within two months. A German intelligence report on the matter was prepared in 1934 by Korvettenkapitän Kleikamp which concluded that the loss of Magdeburg's codebook had been disastrous, not least because no steps were taken after the loss to introduce new secure codes.
The HVB was originally issued in 1913 to all warships with wireless, to naval commands and coastal stations. It was also given to the head offices of eighteen German steamship companies to issue to their own ships with wireless. The code used 450,000 possible four letter groups which allowed alternative representations of the same meaning, plus an alternate ten letter grouping for use in cables. Reciphering was again used but for general purposes was more straightforward although changed more frequently. The code was used particularly by light forces such as patrol boats, and for routine matters such as leaving and entering harbour. The code was used by U-boats, but with a more complex key. However, the complications of their being at sea for long periods meant that codes changed while they were away and quite often messages had to be repeated using the old key, giving immediate information about the new one. German intelligence were aware in November 1914 that the HVB code had fallen into enemy hands, as evidenced by wireless messages sent out warning that the code was compromised, but it was not replaced until 1916.
The HVB was replaced in 1916 by the Allgemeinefunkspruchbuch (AFB) together with a new method of keying. The British obtained a good understanding of the new keying from test signals before it was introduced for real mesages. The new code was issued to even more organisations than the previous one, including in Turkey, Bulgaria and Russia. It had more groups than its predecessor but now of only two letters. The first copy to be captured came from a downed Zeppelin but others were recovered from sunk U-boats
. In the middle of October 1914 a battle was ongoing for control of the coastal towns of Dixmude and Dunkirk. The British navy took part by bombarding German positions from the sea, and German destroyers were ordered to attack the British ships. On 17 October Captain Cecil Fox commanding the light cruiser Undaunted
together with four destroyers, , Lennox
, Legion
and Loyal
was ordered to intercept an anticipated German attack and met four German destroyers (S115, S117, S118, and S119) heading south from The Texel with instructions to lay mines. The German ships were outclassed and all were sunk after a brief battle, whereupon the commander of S119 threw overboard all secret papers in a lead lined chest. The matter was dismissed by both sides believing the papers had been destroyed along with the ships. However, on 30 November a British trawler dragged up the chest which was passed to Room 40 (Hall later claimed the vessel had been searching deliberately). It contained a copy of the Verkehrsbuch (VB) codebook, normally used by Flag officers of the German Navy. Thereafter the event was referred to by Room 40 as 'the miraculous draft of fishes'.
The code consisted of 100,000 groups of 5 digit numbers each with a particular meaning. It had been intended for use in cables sent overseas to warships and naval attachés, embassies and consulates. It was used by senior naval officers with an alternative 'lambda' key, all of which failed to explain its presence on a small destroyer at the start of the war. Its greatest importance during the war was that it allowed access to communications between naval attachés in Berlin, Madrid, Washington, Buenos Aires, Peking, and Constantinople.
In 1917 naval officers switched to a new code with a new key 'Nordo' for which only 70 messages were intercepted, but the code was also broken. For other purposes VB continued in use throughout the war. Reciphering of the code was accomplished using a key made up of a codeword transmitted as part of the message and its date written in German. These were written down in order, and then the letters in this key were each numbered according to their order of appearance in the alphabet. This now produced a set of numbered columns in an apparently random order. The coded message would be written out below these boxes starting top left and continuing down the page once a row was filled. The final message was produced by taking the column numbered '1' and reading off its contents downward, then adding on the second column's digits, and so on. In 1918 the key was changed by using the keywords in a different order. This new cipher was broken within a few days by Professor Walter Horace Bruford
, who had started working for room 40 in 1917 and specialised in VB messages. Two messages were received of identical length, one in the new system and one in the old, allowing the changes to be compared.
was appointed as the new DID to replace Oliver, who had first been transferred to Naval Secretary to the First Lord and then Chief of the Admiralty War Staff. Hall had formerly been captain of the battlecruiser Queen Mary
but had been forced to give up sea duties due to ill health. Hall was to prove an extremely successful DID, although his appointment had been a fortuitous one.
Once the new organisation began to develop and show results it became necessary to place it on a more formal basis than squatting in Ewing's office. On 6 November 1914 the organisation moved to Room 40 in the Admiralty old building
, which was by default to give it its name. Room 40 has since been renumbered, but still exists in the original Admiralty building off Whitehall, London, on the first floor, with windows looking inwards to a courtyard wholly enclosed by admiralty buildings. Previous occupants of the room had complained that no one was ever able to find it, but it was on the same corridor as the Admiralty boardroom and the First Sea Lord's office (Sir John Fisher), who was one of the few people allowed to know of its existence. Adjacent was the First Lord's residence (then Winston Churchill
), who was another. Others permitted to know of the existence of a signals interception unit were the Second Sea Lord, Secretary of the Admiralty, the Chief of Staff (Oliver), the Director of Operations Division (DOD), assistant director, Director of Intelligence Division (DID, Captain William Hall
) and three duty captains. Admiral Sir Arthur Wilson, a retired First Sea Lord, had returned to the admiralty to work with the staff and was also included in the secret. The Prime Minister may also have been informed.
All messages received and decoded were to be kept completely secret, with copies only being passed to the Chief of Staff and Director of Intelligence. It was decided that someone from the intelligence department needed to be appointed to review all the messages and interpret them from the perspective of other information. Rotter was initially suggested for the job, but it was felt preferable to retain him codebreaking and Commander Herbert Hope was chosen, who had previously been working on plotting the movements of enemy ships. Hope was initially placed in a small office in the west wing of the admiralty in the intelligence section and waited patiently for the few messages which were approved for him to see. Hope reports that he attempted to make sense of what he was given and make useful observations about them, but without access to the wider information being received his early remarks were generally unhelpful. He reported to Hall that he needed more information, but Hall was unable to help. On 16 November, after a chance meeting with Fisher where he explained his difficulties, Hope was granted full access to the information together with instructions to make twice daily reports to the First Sea lord. Hope knew nothing of cryptanalysis
or German, but working with the codebreakers and translators he brought detailed knowledge of naval procedures to the process, enabling better translations and then interpretations of received messages. In the interests of secrecy the intention to give a separate copy of messages to the DID was dispensed with so that only the COS received one, who was to show it to the First Sea Lord and Arthur Wilson.
As the number of intercepted messages increased it became part of Hope's duties to decide which were unimportant and should just be logged, and which should be passed on outside Room 40. The German fleet was in the habit each day of wirelessing the exact position of each ship and giving regular position reports when at sea. It was possible to build up a precise picture of the normal operation of the High Seas Fleet, indeed to infer from the routes they chose where defensive minefields had been place and where it was safe for ships to operate. Whenever a change to the normal pattern was seen, it immediately signalled that some operation was about to take place and a warning could be given. Detailed information about submarine movements was available. Most of this information, however, was retained wholly within Room 40 although a few senior members of the admiralty were kept informed, as a huge priority was placed by the Staff upon keeping secret the British ability to read German transmissions. Jellicoe, commanding the Grand Fleet, on three occasions requested from the admiralty that he should have copies of the codebook which his cruiser had brought back to Britain, so that he could make use of it intercepting German signals. Although he was aware that interception was taking place, little of the information ever got back to him, or did so very slowly. No messages based upon Room 40 information were sent out except approved by Oliver personally (except for a few authorised by the First Lord or First Sea Lord). Although it might have been impractical and unwise for codebreaking to have taken place onboard ship, members of room 40 were of the view that full use was not being made of the information they had collected, because of the extreme secrecy and being forbidden to exchange information with the other intelligence departments or those planning operations.
The German navy knew of British direction finding radio and in part this acted as a cover when information about German ship positions was released for operational use. The two sources of information, from directional fixes and from the German's own reports of their positions, complemented each other. Room 40 was able to observe, from intercepted wireless traffic from Zeppelins which were given position fixes by German directional stations to help their navigation, that the accuracy of British systems was better than their German counterparts. This was explainable by the wider baseline used in British equipment.
Room 40 had very accurate information on the positions of German ships, but the admiralty priority remained to keep the existence of this knowledge secret. Initially Hope was shown the regular reports created by the Intelligence Division about German ship whereabouts so that he might correct them. This practice was shortly discontinued for fear of giving away their accurate knowledge. From June 1915 the regular intelligence reports of ship positions ceased to be passed to all flag officers, but only to Jellicoe himself. Similarly, he was the only person to receive accurate charts of German minefields prepared from Room 40 information. Some information was passed to Beatty (commanding the battlecruisers), Tyrwhitt
(Harwich destroyers
) and Keyes (submarines), but Jellicoe was unhappy with the arrangement. He requested that Beatty should be issued with the 'cypher B' reserved for secret messages between the admiralty and himself so that he could communicate more freely and continued to complain that he was not getting sufficient information. All ships were under instructions to use radio as sparingly as possible and to use the lowest practical transmission power. Room 40 had benefited greatly from the free chatter between German ships which gave them many routine messages to compare and analyse, and from the German habit of transmitting always at full power making the messages easier to receive. Messages to Scapa were never to be sent by wireless, and when the fleet was at sea messages might be sent using lower power and relay ships (including private vessels) to make German interception more difficult. No attempts were made by the German fleet to restrict its use of wireless until 1917, and then only in response to perceived British use of direction finding, not because it believed messages were being decoded.
Room 40 played an important role in several naval engagements during the war, notably in detecting major German sorties into the North Sea
that led to the battles of Dogger Bank
and Jutland
as the British fleet was sent out to intercept them. However its most important contribution was probably in decrypting
the Zimmermann Telegram
, a telegram from the German Foreign Office sent via Washington to its ambassador
Heinrich von Eckardt
in Mexico
.
This interception had been made possible a few hours after Britain entered the war by the cable ship Alert (though often incorrectly attributed to the Telconia
), which stood off the German coast and cut the five telegraph cables connecting Germany with Spain, Tenerife
and New York.
In the telegram's plaintext
, Nigel de Grey
and William Montgomery
learned of the German Foreign Minister Arthur Zimmermann
's offer to Mexico of United States
' territories of Arizona, New Mexico, and Texas as an enticement to join the war as a German ally. The telegram was passed to the U.S. by Captain Hall, and a scheme was devised (involving a still unknown agent in Mexico and a burglary) to conceal how its plaintext
had become available and also how the U.S. had gained possession of a copy. The telegram was made public by the United States, which declared war on Germany on 6 April 1917, entering the war on the Allied side.
, Francis Birch
, Walter Horace Bruford
, William Nobby Clarke
, Alastair Denniston
, Frank Cyril Tiarks
and Dilly Knox
.
's intelligence unit MI1
b to form the Government Code and Cypher School (GCCS), later housed at Bletchley Park
during the Second World War and subsequently renamed Government Communications Headquarters (GCHQ)
and relocated to Cheltenham
.
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
, Room 40 (latterly NID25) was the section in the Admiralty
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
most identified with the British cryptoanalysis effort during the First World War
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
.
Room 40 was formed in October 1914, shortly after the start of the war. Admiral Oliver
Henry Oliver
Admiral of the Fleet Sir Henry Francis Oliver, GCB, KCMG, MVO was a British naval officer.-Naval career:...
, the Director of Naval Intelligence, gave intercepts from the German radio station at Nauen
Nauen
Nauen is a town in the Havelland district, in Brandenburg, Germany. It is situated 38 km west of Berlin and 26 km northwest of Potsdam.-History:...
, near Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
, to Director of Naval Education Alfred Ewing
James Alfred Ewing
Sir James Alfred Ewing KCB FRS FRSE MInstitCE was a Scottish physicist and engineer, best known for his work on the magnetic properties of metals and, in particular, for his discovery of, and coinage of the word, hysteresis.It was said of Ewing that he was 'Careful at all times of his appearance,...
, who constructed ciphers as a hobby. Ewing recruited civilians such as William Montgomery, a translator of theological works from German, and Nigel de Grey
Nigel de Grey
Nigel de Grey , CMG, OBE, British codebreaker. Son of the rector of Copdock, Suffolk, and grandson of the 5th Lord Walsingham, he was educated at Eton College and became fluent in French and German. In 1907 he joined the publishing firm of William Heinemann. He married in 1910...
, a publisher.
The basis of Room 40 operations evolved around a German naval codebook, the Signalbuch der Kaiserlichen Marine (SKM), and maps (containing coded squares), which had been passed on to the Admiralty by the Russians. The Russians had seized them from the German cruiser Magdeburg
SMS Magdeburg
Seiner Majestät Schiff Magdeburg was a light cruiser of the German Imperial Navy. The first of her class, she was built as part of the 1908 German naval program. Her class was notable for being the first to introduce a new hull form and replace the bow ram with a cruiser bow shape...
when it ran aground off the Estonia
Estonia
Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
n coast on 26 August 1914. Two of the four copies that the warship had been carrying were recovered; one was retained by the Russians and the other passed to the British.
In October, 1914, the British also obtained the Imperial German Navy's Handelsschiffsverkehrsbuch (HVB), a codebook used by German naval warships, merchantmen, naval zeppelin
Zeppelin
A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on 14 March 1899...
s and U-Boat
U-boat
U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...
s. This had been captured from the German steamer Hobart by the Royal Australian Navy
Royal Australian Navy
The Royal Australian Navy is the naval branch of the Australian Defence Force. Following the Federation of Australia in 1901, the ships and resources of the separate colonial navies were integrated into a national force: the Commonwealth Naval Forces...
on 11 October. On 30 November a British trawler recovered a safe from the sunken German destroyer S-119, in which was found the Verkehrsbuch (VB), the code used by the Germans to communicate with naval attachés, embassies and warships overseas.
In March, 1915, the luggage of Wilhelm Wassmuss
Wilhelm Wassmuss
Wilhelm Wassmuss was a German diplomat, also known as the "Wassmuss of Persia". He attempted to foment trouble for the British in the Persian Gulf in the First World War.- Birth and schooling :...
, a German agent in Persia, was captured and shipped, unopened, to London, where then-Director of Naval Intelligence Admiral Sir William Reginald Hall
William Reginald Hall
Admiral Sir William Reginald Hall, KCMG, CB, RN was the British Director of Naval Intelligence from 1914 to 1919...
discovered that it contained the German Diplomatic Code Book, Code No. 13040.
The function of the program was compromised by the Admiralty's insistence upon interpreting Room 40 information in its own way. Room 40 operators were permitted to decrypt, but not to interpret the information they acquired.
The section retained "Room 40" as its informal name even though it expanded during the war and moved into other offices. It has been estimated that Room 40 decrypted around 15,000 German communications, the section being provided with copies of all intercepted communications traffic, including wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
and telegraph traffic. Until May 1917 it was directed by Alfred Ewing, and then direct control passed to Captain
Captain (Royal Navy)
Captain is a senior officer rank of the Royal Navy. It ranks above Commander and below Commodore and has a NATO ranking code of OF-5. The rank is equivalent to a Colonel in the British Army or Royal Marines and to a Group Captain in the Royal Air Force. The rank of Group Captain is based on the...
(later Admiral) Reginald 'Blinker' Hall
William Reginald Hall
Admiral Sir William Reginald Hall, KCMG, CB, RN was the British Director of Naval Intelligence from 1914 to 1919...
, assisted by William Milbourne James
William Milbourne James
Admiral Sir William Milbourne James GCB was a British Naval commander, politician and author, perhaps most notable for his activities in the Naval Intelligence Division in the First World War.-Family:...
.
Origins
In 1911, a committee of the Committee of Imperial DefenceCommittee of Imperial Defence
The Committee of Imperial Defence was an important ad hoc part of the government of the United Kingdom and the British Empire from just after the Second Boer War until the start of World War II...
on cable communications concluded that in the event of war with Germany, German-owned submarine cables should be destroyed. On the night of 3 August, 1914, the cable ship Alert located and cut Germany's five trans-Atlantic cables, which ran down the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
. Soon after, the six cables running between Britain and Germany were cut. As an immediate consequence, there was a significant increase in cable messages sent via cables belonging to other countries, and cables sent by wireless. These could now be intercepted, but codes and ciphers were naturally used to hide the meaning of the messages, and neither Britain nor Germany had any established organisations to decode and interpret the messages. At the start of the war, the navy had only one wireless station for intercepting messages, at Stockton. However, installations belonging to the post Office and the Marconi Company, as well as private individuals who had access to radio equipment, began recording messages from Germany.
Intercepted messages began to arrive at the Admiralty intelligence division, but no one knew what to do with them. Rear-Admiral Henry Oliver
Henry Oliver
Admiral of the Fleet Sir Henry Francis Oliver, GCB, KCMG, MVO was a British naval officer.-Naval career:...
had been appointed Director of the Intelligence division in 1913. In August, 1914, his department was fully occupied with the war and none had experience codebreaking. Instead he turned to a friend, Sir Alfred Ewing
James Alfred Ewing
Sir James Alfred Ewing KCB FRS FRSE MInstitCE was a Scottish physicist and engineer, best known for his work on the magnetic properties of metals and, in particular, for his discovery of, and coinage of the word, hysteresis.It was said of Ewing that he was 'Careful at all times of his appearance,...
, the Director of Naval Education (DNE), who previously had been a professor of engineering with a knowledge of radio communications and who he knew had an interest in ciphers. It was not felt that education would be a priority during the expected few months duration of the war, so Ewing was asked to set up a group for decoding messages. Ewing initially turned to staff of the naval colleges Osborne and Dartmouth who were currently available due both to the school holidays and to naval students having been sent on active duty. Alastair Denniston
Alastair Denniston
Commander Alexander Guthrie Denniston CMG CBE RNVR was a British codebreaker in Room 40 and first head of the Government Code and Cypher School and field hockey player...
had been teaching German but later became second in charge of Room 40, then becoming Chief of its successor after the First World War, the Government Code and Cypher School (located at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
during the Second World War). Others from the schools worked temporarily for Room 40 until the start of the new term at the end of September. These included Charles Godfrey, the Headmaster of Osborne (whose brother became head of naval Intelligence during the Second World War), two Naval instructors, Parish and Curtiss and scientist and mathematician Professor Henderson from Greenwich Naval College. Volunteers had to work at codebreaking alongside their normal duties, the whole organisation operating from Ewing's ordinary office where codebreakers had to hide in his secretary's room whenever there were visitors concerning the ordinary duties of the DNE. Two other early recruits included R. D. Norton who had worked for the Foreign Office, and Lord Herschell
Richard Herschell, 2nd Baron Herschell
Richard Farrer Herschell, 2nd Baron Herschell GCVO , was a British Liberal politician.Herschell was the only son of Lord Chancellor Farrer Herschell, 1st Baron Herschell, and his wife Agnes Adela , and succeeded in the barony in 1899...
, who was a linguist, an expert on Persia and an Oxford graduate. None of the recruits knew anything about codebreaking, but were chosen for a knowledge of German and a certainty they could keep the matter secret.
A similar organisation had begun in the Military intelligence department of the War Office
War Office
The War Office was a department of the British Government, responsible for the administration of the British Army between the 17th century and 1964, when its functions were transferred to the Ministry of Defence...
, which become known as MI1b, and Colonel Macdonagh proposed that the two organisations should work together. Little success was achieved except to organise a system for collecting and filing messages until the French obtained copies of German military ciphers. The two organisations operated in parallel, decoding messages concerning the Western Front
Western Front (World War I)
Following the outbreak of World War I in 1914, the German Army opened the Western Front by first invading Luxembourg and Belgium, then gaining military control of important industrial regions in France. The tide of the advance was dramatically turned with the Battle of the Marne...
. A friend of Ewing's, a barrister by the name of Russell Clarke, plus a friend of his, Colonel Hippisley, approached Ewing to explain that they had been intercepting German messages. Ewing arranged for them to operate from the coastguard station at Hunstanton in Norfolk, where they were joined by another volunteer, Leslie Lambert (later becoming known as a BBC broadcaster under the name A. J. Alan). Hunstanton and Stockton formed the core of the interception service (known as 'Y' service), together with the post office and Marconi stations, which grew rapidly to the point it could intercept almost all official German messages. At the end of September, the volunteer schoolmasters returned to other duties except for Denniston, but without a means to decode German naval messages there was little specifically naval work to do.
Loss of the Magdeburg and capture of the SKM codebook
The first breakthrough for room 40 came with the capture of the Signalbuch der Kaiserlich Marine (SKM) from the German Light cruiser MagdeburgSMS Magdeburg
Seiner Majestät Schiff Magdeburg was a light cruiser of the German Imperial Navy. The first of her class, she was built as part of the 1908 German naval program. Her class was notable for being the first to introduce a new hull form and replace the bow ram with a cruiser bow shape...
. Two light cruisers, Magdeburg and Augsberg
SMS Augsburg
The SMS Augsburg was a Kolberg class light cruiser of the German Kaiserliche Marine. Named after the city of Augsburg, she was laid down at the Kaiserliche Werft Kiel in 1908, launched on 10 July 1909 and commissioned 1 November 1910....
and a group of destroyers all commanded by Rear-Admiral Behring were carrying out a reconnaissance of the Gulf of Finland when the ships became separated in fog. Magdeburg ran aground on the island of Odensholm off the coast of Russian controlled Estonia
Estonia
Estonia , officially the Republic of Estonia , is a state in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia , and to the east by Lake Peipsi and the Russian Federation . Across the Baltic Sea lies...
. The ship could not be refloated so the crew was to be taken onboard by the destroyer SMS V26. The commander, Korvettenkapitän Habenicht prepared to blow up the ship after it had been evacuated, but the fog began to clear and two Russian cruisers Pallada and Bogatyr
Russian cruiser Bogatyr
Bogatyr was the lead ship of the Bogatyr-class of four protected cruisers built for the Imperial Russian Navy. Her name can be translated to mean “Hercules”.-Background:...
approached and opened fire. The demolition charges were set off prematurely, causing injuries amongst the crew still on board, and before secret papers could be transferred to the destroyer or otherwise properly disposed of. Habenicht and fifty seven of his crew were captured by the Russians.
Exactly what happened to the papers is not clear. The ship carried more than one copy of the SKM codebook, and copy number 151 was passed to the British. The German account is that most of the secret papers were thrown overboard, but the British copy was undamaged and was reportedly found in the charthouse. The current key was also needed in order to use the codebook. A gridded chart of the Baltic, the ships log and war diaries were all also recovered. Copies numbered 145 and 974 of the SKM were retained by the Russians while was dispatched from Scapa Flow
Scapa Flow
right|thumb|Scapa Flow viewed from its eastern endScapa Flow is a body of water in the Orkney Islands, Scotland, United Kingdom, sheltered by the islands of Mainland, Graemsay, Burray, South Ronaldsay and Hoy. It is about...
to Alexandrovosk in order to collect the copy offered to the British. Although she arrived on 7 September, due to mixups she did not depart until 30 September and returned to Scapa with Captain Kredoff, Commander Smirnoff and the documents on 10 October. The books were formally handed over to the First Lord, Winston Churchill, on 13 October.
The SKM by itself was incomplete as a means of decoding messages since they were normally enciphered as well as coded, and those that could be understood were mostly weather reports. Fleet paymaster C. J. E. Rotter, a German expert from the naval intelligence division, was tasked with using the SKM codebook to interpret intercepted messages, most of which decoded as nonsense since initially it was not appreciated that they were also enciphered. An entry into solving the problem was found from a series of messages transmitted from the German Norddeich transmitter, which were all numbered sequentially and then re-enciphered. The cipher was broken, in fact broken twice as it was changed a few days after it was first solved, and a general procedure for interpreting the messages determined. Enciphering was by a simple table, substituting one letter with another throughout all the messages. Rotter started work in mid October but was kept apart from the other codebreakers until November after he had broken the cipher.
The intercepted messages were found to be intelligence reports on the whereabouts of allied ships. This was interesting, but not vital. Russel Clarke now observed that similar coded messages were being transmitted on short wave, but were not being intercepted because of shortages of receiving equipment, in particular the aerial. Hunstanton was directed to stop listening to the military signals it had been intercepting and instead monitor shortwave for a test period of one weekend. The result was information about the movements of the High seas fleet, and valuable naval intelligence. Hunstanton was now permanently switched to the naval signals and as a result stopped receiving messages valuable to the military. Navy men who had been helping the military were withdrawn to work on the naval messages, without explaining why because the new code was kept entirely secret; and the result was bad feeling between the naval and military interception services and a cessation of cooperation between them, which continued to 1917.
The SKM (sometimes abbreviated SB in German documents) was the code normally used during important actions by the German fleet. It was derived from the ordinary fleet signal books used by both British and German navies, which had thousands of predetermined instructions which could be represented by simple combinations of signal flags or lamp flashes for transmission between ships. There were 34,300 instructions each represented by a different group of three letters. A number of these reflected old-fashioned naval operations, and did not mention modern inventions such as aircraft. Ships were identified by a three letter grouping beginning with a Beta symbol. Messages not covered by the predetermined list could be spelled out using a substitution table for individual letters. The signals used four symbols not present in ordinary Morse code (given the names alpha beta gamma and rho), which caused some confusion until all those involved in interception learnt to recognise them and use a standardised way to write them.
The sheer size of the book was one reason it could not easily be changed and the code continued in use until summer 1916. Even then ships at first refused to use the new codebook because the replacement was too complicated, so the Flottenfunkspruchbuch (FFB) did not fully replace the SKB until May 1917. Doubts about the security of the SKB were initially raised by Behring, who reported that it was not definitely known whether Magdeburg's code books had been destroyed or not, and it was suggested at the court martial enquiry into the loss that books might anyway have been recovered by Russians from the clear shallow waters where the ship had grounded. Prince Henry of Prussia
Prince Heinrich of Prussia
Prince Henry of Prussia was a younger brother of German Emperor William II and a Prince of Prussia...
, commander in chief of Baltic operations, wrote to the C-in-C of the HSF that in his view it was a certainty that secret charts had fallen into the hands of the Russians, and a probability that the codebook and key had also. The German navy relied upon the reenciphering process to ensure security, but the key used for this was not changed until 20 October and then not changed again for another three months. The actual substitution table used for enciphering was produced by a mechanical device with slides and compartments for the letters. Orders to change the key were sent out by wireless, and frequently confusion during the changeover period led to messages being sent out using the new cipher and then being repeated with the old. Key changes continued to occur infrequently, only 6 times during 1915 from March to the end of the year, but then more frequently from 1916.
There was no immediate capture of the FFB codebook to help the admiralty understand it, but instead a careful study was made of new and old messages, particularly from the Baltic, which allowed a new book to be reconstructed. Now that the system was understood, Room 40 reckoned to crack a new key within three to four days, and to have reproduced the majority of a new codebook within two months. A German intelligence report on the matter was prepared in 1934 by Korvettenkapitän Kleikamp which concluded that the loss of Magdeburg's codebook had been disastrous, not least because no steps were taken after the loss to introduce new secure codes.
Steamer Hobart and capture of the HVB codebook
The second important code used by the German navy was captured at the very start of the war in Australia, although it did not reach the admiralty until the end of October. The German-Australian steamer Hobart was seized off Port Philip Heads near Melbourne on 11 August 1914. Hobart had not received news that war had broken out, and Captain J. T. Richardson and party claimed to be a quarantine inspection team. Hobarts crew were allowed to go about the ship but the captain was closely observed, until in the middle of the night he attempted to dispose of hidden papers. The Handelsverkehrsbuch (HVB) codebook was captured, which contained the code used by the German navy to communicate with its merchant ships and also within the High Seas Fleet. News of the capture was not passed to London until 9 September. A copy of the book was made and sent by the fastest available steamer, arriving end of October.The HVB was originally issued in 1913 to all warships with wireless, to naval commands and coastal stations. It was also given to the head offices of eighteen German steamship companies to issue to their own ships with wireless. The code used 450,000 possible four letter groups which allowed alternative representations of the same meaning, plus an alternate ten letter grouping for use in cables. Reciphering was again used but for general purposes was more straightforward although changed more frequently. The code was used particularly by light forces such as patrol boats, and for routine matters such as leaving and entering harbour. The code was used by U-boats, but with a more complex key. However, the complications of their being at sea for long periods meant that codes changed while they were away and quite often messages had to be repeated using the old key, giving immediate information about the new one. German intelligence were aware in November 1914 that the HVB code had fallen into enemy hands, as evidenced by wireless messages sent out warning that the code was compromised, but it was not replaced until 1916.
The HVB was replaced in 1916 by the Allgemeinefunkspruchbuch (AFB) together with a new method of keying. The British obtained a good understanding of the new keying from test signals before it was introduced for real mesages. The new code was issued to even more organisations than the previous one, including in Turkey, Bulgaria and Russia. It had more groups than its predecessor but now of only two letters. The first copy to be captured came from a downed Zeppelin but others were recovered from sunk U-boats
Loss of German destroyer S119 and capture of the VB codebook
A third codebook was recovered following the sinking of German destroyer SMS S119 in a battle off Texel islandBattle off Texel
The Battle off Texel, also known as the Action off Texel or the Action of 17 October 1914, was a naval battle off the coast of the Dutch island of Texel during the First World War where a British squadron consisting of one light cruiser and four destroyers on a routine patrol encountered the...
. In the middle of October 1914 a battle was ongoing for control of the coastal towns of Dixmude and Dunkirk. The British navy took part by bombarding German positions from the sea, and German destroyers were ordered to attack the British ships. On 17 October Captain Cecil Fox commanding the light cruiser Undaunted
HMS Undaunted (1914)
HMS Undaunted was an Arethusa-class light cruiser of the Royal Navy launched on 28 April 1914 at Fairfield Shipbuilding and Engineering Company's shipyard at Govan.Undaunted participated in numerous naval operations during the First World War...
together with four destroyers, , Lennox
HMS Lennox (1914)
HMS Lennox was a Laforey class destroyer of the Royal Navy. Launched prior to the outbreak of the First World War, she was attached to the Harwich Force and served in the North Sea. Lennox saw action in several engagements, including the Battle off Texel.-Specifications:Lennox was laid down as HMS...
, Legion
HMS Legion (1914)
HMS Legion was a Laforey-class destroyer of the Royal Navy. Launched prior to the outbreak of the First World War, she was attached to the Harwich Force and served in the North Sea...
and Loyal
HMS Loyal (1913)
HMS Loyal was a Laforey class destroyer of the Royal Navy. Launched prior to the First World War, she was attached to the Harwich Force and served in the North Sea. Loyal saw action in several engagements, including the Battle off Texel....
was ordered to intercept an anticipated German attack and met four German destroyers (S115, S117, S118, and S119) heading south from The Texel with instructions to lay mines. The German ships were outclassed and all were sunk after a brief battle, whereupon the commander of S119 threw overboard all secret papers in a lead lined chest. The matter was dismissed by both sides believing the papers had been destroyed along with the ships. However, on 30 November a British trawler dragged up the chest which was passed to Room 40 (Hall later claimed the vessel had been searching deliberately). It contained a copy of the Verkehrsbuch (VB) codebook, normally used by Flag officers of the German Navy. Thereafter the event was referred to by Room 40 as 'the miraculous draft of fishes'.
The code consisted of 100,000 groups of 5 digit numbers each with a particular meaning. It had been intended for use in cables sent overseas to warships and naval attachés, embassies and consulates. It was used by senior naval officers with an alternative 'lambda' key, all of which failed to explain its presence on a small destroyer at the start of the war. Its greatest importance during the war was that it allowed access to communications between naval attachés in Berlin, Madrid, Washington, Buenos Aires, Peking, and Constantinople.
In 1917 naval officers switched to a new code with a new key 'Nordo' for which only 70 messages were intercepted, but the code was also broken. For other purposes VB continued in use throughout the war. Reciphering of the code was accomplished using a key made up of a codeword transmitted as part of the message and its date written in German. These were written down in order, and then the letters in this key were each numbered according to their order of appearance in the alphabet. This now produced a set of numbered columns in an apparently random order. The coded message would be written out below these boxes starting top left and continuing down the page once a row was filled. The final message was produced by taking the column numbered '1' and reading off its contents downward, then adding on the second column's digits, and so on. In 1918 the key was changed by using the keywords in a different order. This new cipher was broken within a few days by Professor Walter Horace Bruford
Walter Horace Bruford
Walter Horace Bruford, FBA was a British scholar of German literature.Walter Horace Bruford was born in Manchester in 1894. He was educated at Manchester Grammar School and then he studied at St. John's College, Cambridge, and also at the University of Zurich, Switzerland...
, who had started working for room 40 in 1917 and specialised in VB messages. Two messages were received of identical length, one in the new system and one in the old, allowing the changes to be compared.
Formal organisation, Room 40
In early November Captain William HallWilliam Reginald Hall
Admiral Sir William Reginald Hall, KCMG, CB, RN was the British Director of Naval Intelligence from 1914 to 1919...
was appointed as the new DID to replace Oliver, who had first been transferred to Naval Secretary to the First Lord and then Chief of the Admiralty War Staff. Hall had formerly been captain of the battlecruiser Queen Mary
HMS Queen Mary
HMS Queen Mary was a battlecruiser built by the British Royal Navy before World War I, the sole member of her class. She was similar to the s, though she differed in details from her half-sisters. She was the last battlecruiser completed before the war and participated in the Battle of Heligoland...
but had been forced to give up sea duties due to ill health. Hall was to prove an extremely successful DID, although his appointment had been a fortuitous one.
Once the new organisation began to develop and show results it became necessary to place it on a more formal basis than squatting in Ewing's office. On 6 November 1914 the organisation moved to Room 40 in the Admiralty old building
Admiralty
The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy...
, which was by default to give it its name. Room 40 has since been renumbered, but still exists in the original Admiralty building off Whitehall, London, on the first floor, with windows looking inwards to a courtyard wholly enclosed by admiralty buildings. Previous occupants of the room had complained that no one was ever able to find it, but it was on the same corridor as the Admiralty boardroom and the First Sea Lord's office (Sir John Fisher), who was one of the few people allowed to know of its existence. Adjacent was the First Lord's residence (then Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
), who was another. Others permitted to know of the existence of a signals interception unit were the Second Sea Lord, Secretary of the Admiralty, the Chief of Staff (Oliver), the Director of Operations Division (DOD), assistant director, Director of Intelligence Division (DID, Captain William Hall
William Reginald Hall
Admiral Sir William Reginald Hall, KCMG, CB, RN was the British Director of Naval Intelligence from 1914 to 1919...
) and three duty captains. Admiral Sir Arthur Wilson, a retired First Sea Lord, had returned to the admiralty to work with the staff and was also included in the secret. The Prime Minister may also have been informed.
All messages received and decoded were to be kept completely secret, with copies only being passed to the Chief of Staff and Director of Intelligence. It was decided that someone from the intelligence department needed to be appointed to review all the messages and interpret them from the perspective of other information. Rotter was initially suggested for the job, but it was felt preferable to retain him codebreaking and Commander Herbert Hope was chosen, who had previously been working on plotting the movements of enemy ships. Hope was initially placed in a small office in the west wing of the admiralty in the intelligence section and waited patiently for the few messages which were approved for him to see. Hope reports that he attempted to make sense of what he was given and make useful observations about them, but without access to the wider information being received his early remarks were generally unhelpful. He reported to Hall that he needed more information, but Hall was unable to help. On 16 November, after a chance meeting with Fisher where he explained his difficulties, Hope was granted full access to the information together with instructions to make twice daily reports to the First Sea lord. Hope knew nothing of cryptanalysis
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
or German, but working with the codebreakers and translators he brought detailed knowledge of naval procedures to the process, enabling better translations and then interpretations of received messages. In the interests of secrecy the intention to give a separate copy of messages to the DID was dispensed with so that only the COS received one, who was to show it to the First Sea Lord and Arthur Wilson.
As the number of intercepted messages increased it became part of Hope's duties to decide which were unimportant and should just be logged, and which should be passed on outside Room 40. The German fleet was in the habit each day of wirelessing the exact position of each ship and giving regular position reports when at sea. It was possible to build up a precise picture of the normal operation of the High Seas Fleet, indeed to infer from the routes they chose where defensive minefields had been place and where it was safe for ships to operate. Whenever a change to the normal pattern was seen, it immediately signalled that some operation was about to take place and a warning could be given. Detailed information about submarine movements was available. Most of this information, however, was retained wholly within Room 40 although a few senior members of the admiralty were kept informed, as a huge priority was placed by the Staff upon keeping secret the British ability to read German transmissions. Jellicoe, commanding the Grand Fleet, on three occasions requested from the admiralty that he should have copies of the codebook which his cruiser had brought back to Britain, so that he could make use of it intercepting German signals. Although he was aware that interception was taking place, little of the information ever got back to him, or did so very slowly. No messages based upon Room 40 information were sent out except approved by Oliver personally (except for a few authorised by the First Lord or First Sea Lord). Although it might have been impractical and unwise for codebreaking to have taken place onboard ship, members of room 40 were of the view that full use was not being made of the information they had collected, because of the extreme secrecy and being forbidden to exchange information with the other intelligence departments or those planning operations.
Signal Interception and direction finding
Both the British and German interception services began to experiment with direction finding radio equipment in the start of 1915. Captain Round working for Marconi had been carrying out experiments for the army in France and Hall instructed him to build a direction finding system for the navy. This was sited at Chelmsford but the location proved a mistake and the equipment was moved to Lowestoft. Now successful, other stations were built at Lerwick, Aberdeen, York, Flamborough Head and Birchington and by May 1915 the admiralty was able to track German submarines crossing the North Sea. Some of these stations also acted as 'Y' stations to collect German messages, but a new section was created within Room 40 to plot the positions of ships from the directional reports. A separate set of five stations was created in Ireland under the command of the Vice Admiral at Queenstown for plottting ships in the seas to the west of Britain and further stations both within Britain and overseas were operated by the Admiral commanding reserves.The German navy knew of British direction finding radio and in part this acted as a cover when information about German ship positions was released for operational use. The two sources of information, from directional fixes and from the German's own reports of their positions, complemented each other. Room 40 was able to observe, from intercepted wireless traffic from Zeppelins which were given position fixes by German directional stations to help their navigation, that the accuracy of British systems was better than their German counterparts. This was explainable by the wider baseline used in British equipment.
Room 40 had very accurate information on the positions of German ships, but the admiralty priority remained to keep the existence of this knowledge secret. Initially Hope was shown the regular reports created by the Intelligence Division about German ship whereabouts so that he might correct them. This practice was shortly discontinued for fear of giving away their accurate knowledge. From June 1915 the regular intelligence reports of ship positions ceased to be passed to all flag officers, but only to Jellicoe himself. Similarly, he was the only person to receive accurate charts of German minefields prepared from Room 40 information. Some information was passed to Beatty (commanding the battlecruisers), Tyrwhitt
Reginald Tyrwhitt
Admiral of the Fleet Sir Reginald Yorke Tyrwhitt, 1st Baronet, GCB, DSO was a senior officer of the Royal Navy in World War I who commanded light forces stationed at Harwich on the east coast of England during the first part of the war.-Naval career:Tyrwhitt entered the Navy as a cadet in July, 1885...
(Harwich destroyers
Harwich Force
The Harwich Force was a squadron of the Royal Navy, formed during the First World War, that went on to play a significant role in the war.-History:...
) and Keyes (submarines), but Jellicoe was unhappy with the arrangement. He requested that Beatty should be issued with the 'cypher B' reserved for secret messages between the admiralty and himself so that he could communicate more freely and continued to complain that he was not getting sufficient information. All ships were under instructions to use radio as sparingly as possible and to use the lowest practical transmission power. Room 40 had benefited greatly from the free chatter between German ships which gave them many routine messages to compare and analyse, and from the German habit of transmitting always at full power making the messages easier to receive. Messages to Scapa were never to be sent by wireless, and when the fleet was at sea messages might be sent using lower power and relay ships (including private vessels) to make German interception more difficult. No attempts were made by the German fleet to restrict its use of wireless until 1917, and then only in response to perceived British use of direction finding, not because it believed messages were being decoded.
Zimmermann Telegram
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
that led to the battles of Dogger Bank
Battle of Dogger Bank (1915)
The Battle of Dogger Bank was a naval battle fought near the Dogger Bank in the North Sea on 24 January 1915, during the First World War, between squadrons of the British Grand Fleet and the German High Seas Fleet....
and Jutland
Battle of Jutland
The Battle of Jutland was a naval battle between the British Royal Navy's Grand Fleet and the Imperial German Navy's High Seas Fleet during the First World War. The battle was fought on 31 May and 1 June 1916 in the North Sea near Jutland, Denmark. It was the largest naval battle and the only...
as the British fleet was sent out to intercept them. However its most important contribution was probably in decrypting
Cryptanalysis
Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...
the Zimmermann Telegram
Zimmermann Telegram
The Zimmermann Telegram was a 1917 diplomatic proposal from the German Empire to Mexico to make war against the United States. The proposal was caught by the British before it could get to Mexico. The revelation angered the Americans and led in part to a U.S...
, a telegram from the German Foreign Office sent via Washington to its ambassador
Ambassador
An ambassador is the highest ranking diplomat who represents a nation and is usually accredited to a foreign sovereign or government, or to an international organization....
Heinrich von Eckardt
Heinrich von Eckardt
Heinrich von Eckardt was the ambassador for the German Empire in Mexico, assuming office around 1915 and spending most of his time as ambassador during World War I...
in Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
.
This interception had been made possible a few hours after Britain entered the war by the cable ship Alert (though often incorrectly attributed to the Telconia
Telconia
CS Telconia was an English cable ship used in the early 20th century to lay and repair submarine communications cables. It was built in 1909 by Swan Hunter & Wigham Richardson for the Telegraph Construction and Maintenance Company and remained in service until late 1934..The Telconia is often...
), which stood off the German coast and cut the five telegraph cables connecting Germany with Spain, Tenerife
Tenerife
Tenerife is the largest and most populous island of the seven Canary Islands, it is also the most populated island of Spain, with a land area of 2,034.38 km² and 906,854 inhabitants, 43% of the total population of the Canary Islands. About five million tourists visit Tenerife each year, the...
and New York.
In the telegram's plaintext
Plaintext
In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym. Before the computer era, plaintext most commonly meant message text in the language of the communicating parties....
, Nigel de Grey
Nigel de Grey
Nigel de Grey , CMG, OBE, British codebreaker. Son of the rector of Copdock, Suffolk, and grandson of the 5th Lord Walsingham, he was educated at Eton College and became fluent in French and German. In 1907 he joined the publishing firm of William Heinemann. He married in 1910...
and William Montgomery
William Montgomery (cryptographer)
Rev. William Montgomery was a Presbyterian minister and a British codebreaker who worked in Room 40 during World War I.Montgomery and Nigel de Grey deciphered the Zimmermann Telegram, which helped bring America into World War I. At this time , Montgomery was 46.A Presbyterian minister, he was an...
learned of the German Foreign Minister Arthur Zimmermann
Arthur Zimmermann
Arthur Zimmermann was State Secretary for Foreign Affairs of the German Empire from November 22, 1916, until his resignation on August 6, 1917. His name is associated with the Zimmermann Telegram during World War I...
's offer to Mexico of United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
' territories of Arizona, New Mexico, and Texas as an enticement to join the war as a German ally. The telegram was passed to the U.S. by Captain Hall, and a scheme was devised (involving a still unknown agent in Mexico and a burglary) to conceal how its plaintext
Plaintext
In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym. Before the computer era, plaintext most commonly meant message text in the language of the communicating parties....
had become available and also how the U.S. had gained possession of a copy. The telegram was made public by the United States, which declared war on Germany on 6 April 1917, entering the war on the Allied side.
Staffers
Other staff of Room 40 were Frank AdcockFrank Adcock
Frank Ezra Adcock was a British classical historian of Greece and Rome, and worked as a cryptographer in both World Wars.He was born in Desford, Leicestershire, and died at Cambridge. He was educated at King’s College, Cambridge. He became a fellow and lecturer there in 1911, and held the Chair of...
, Francis Birch
Francis Birch (cryptographer)
Francis Lyall Birch was a British cryptographer. He was educated at Eton and King’s College, Cambridge. He was awarded an OBE in 1919 and CMG in 1945....
, Walter Horace Bruford
Walter Horace Bruford
Walter Horace Bruford, FBA was a British scholar of German literature.Walter Horace Bruford was born in Manchester in 1894. He was educated at Manchester Grammar School and then he studied at St. John's College, Cambridge, and also at the University of Zurich, Switzerland...
, William Nobby Clarke
William Clarke (cryptographer)
William Francis 'Nobby' Clarke was a British intelligence officer and cryptographer of naval codes in both World Wars.In 1915 he was commissioned as an assistant paymaster, having failed the eye examination for executive officer. He knew German, and in March 1916 joined Room 40. His talent was for...
, Alastair Denniston
Alastair Denniston
Commander Alexander Guthrie Denniston CMG CBE RNVR was a British codebreaker in Room 40 and first head of the Government Code and Cypher School and field hockey player...
, Frank Cyril Tiarks
Frank Cyril Tiarks
Frank Cyril Tiarks OBE was an English banker.Tiarks married Emmy Maria Franziska Brödermann of Hamburg, Germany, on 18 November 1899....
and Dilly Knox
Dilly Knox
Alfred Dillwyn 'Dilly' Knox CMG was a classics scholar at King's College, Cambridge, and a British codebreaker...
.
Merger with Military Intelligence (MI)
In 1919, Room 40 was deactivated and its function merged with the British ArmyBritish Army
The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...
's intelligence unit MI1
MI1
MI1 or British Military Intelligence, Section 1 was a department of the British Directorate of Military Intelligence, part of the War Office. It was set up during World War I...
b to form the Government Code and Cypher School (GCCS), later housed at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
during the Second World War and subsequently renamed Government Communications Headquarters (GCHQ)
Government Communications Headquarters
The Government Communications Headquarters is a British intelligence agency responsible for providing signals intelligence and information assurance to the UK government and armed forces...
and relocated to Cheltenham
Cheltenham
Cheltenham , also known as Cheltenham Spa, is a large spa town and borough in Gloucestershire, on the edge of the Cotswolds in the South-West region of England. It is the home of the flagship race of British steeplechase horse racing, the Gold Cup, the main event of the Cheltenham Festival held...
.
External links
- The Papers of William Clarke, who worked in Room 40, are held at Churchill Archives CentreChurchill Archives CentreThe Churchill Archives Centre is one of the largest repositories in the United Kingdom for the preservation and study of modern personal papers. It is best known for housing the Churchill Papers, the massive archive of Sir Winston Churchill, as well as the private papers of Baroness Thatcher...
in Cambridge and are accessible to the public. - The Papers of Alexander Denniston, second in command of Room 40, are also held at Churchill Archives CentreChurchill Archives CentreThe Churchill Archives Centre is one of the largest repositories in the United Kingdom for the preservation and study of modern personal papers. It is best known for housing the Churchill Papers, the massive archive of Sir Winston Churchill, as well as the private papers of Baroness Thatcher...
. - The Papers of William Reginald Hall, joint founder of Room 40, are also held at Churchill Archives CentreChurchill Archives CentreThe Churchill Archives Centre is one of the largest repositories in the United Kingdom for the preservation and study of modern personal papers. It is best known for housing the Churchill Papers, the massive archive of Sir Winston Churchill, as well as the private papers of Baroness Thatcher...
. - Original Documents from Room 40: LUSITANIA case; Naval Battle of Jutland/Skagerrak; The Zimmermann/Mexico Telegram; German Submarine Warfare and Room 40 Intelligence in general; PhotoCopies from The National Archives, Kew, Richmond, UK.