World War I: 100 Years of Espionage

by Ryan Schaum and Māris Goldmanis

Table of Contents

I. Intelligence and Decryption
II. Radio Communications
III. Numbers Stations
IV. Sources


I. Intelligence and Decryption

During WWI many nations did not have a strong intelligence agency.  Britain and the US had a well developed Intelligence system, but out of everyone Germany was the most developed in Military Intel.[11]  There were many advancements in cryptology such as the increase of complexity in mathematical codes sent.  This prompted many countries to improve on their abilities in their Intel department.

A popular way to send codes during WWI was sending coded messages through telegrams.  They were sent by telegraph a copper wires that were laid along the many underwater and land routes all across the world.  By so it was the most effective means of long distance communications on 1914.  The messages were Morse coded, a message had first to be written out for the telegraph operator, transmitted by him, written out again by the receiving operator, and then the message conveyed to the recipient.  Even if code was used, the telegraph line risked being tapped (bugged) by the enemy, the message decoded and read.   

One of the most famous messages during that war was the Zimmerman telegram which was decoded by British Cryptographers.[7]  They were lead by Reginald ‘Blinker’ Hall the head of the British Naval Intelligence.  A former commander of the British cruiser Queen Mary he installed so called Room 40 within the Admiralty in Whitehall.  His new Naval Intelligence office  mastered the breaking of the German naval codes.  That greatly helped the Admiralty and the Naval commanders. Hall then turned to diplomatic telegraphy and on January 16 intercepted the Zimmerman telegram.  It was sent by the minister of Foreign Affairs Arthur Zimmerman who sent it to German ambassador in Washington.  The message contained warning of plans to intensify German U-Boat submarine campaign in the West Atlantic and allow unrestricted warfare against the US neutral merchant ships.  Germans accused them of sending war supplies to UK and France.  After the disastrous sinking of passenger liner Lusitania (that was actually carrying secret war supplies) such an act was viewed most ferociously by the US government.

Another  point of this telegram was a suggestion  to create a alliance between Mexico and Germany to launch a invasion in US territory by the Mexican forces. Such scandalous suggestion was seen as gold mine by Hall to finally push the indecisive US government into war with Germany.   The telegram was sent through a transatlantic cable that used a relay station in Portcurno, Cornwall.  After being intercepted, it was sent to Room 40 to decipher.[8]  The German diplomatic code known as 0075 was only partially broken by the British and only a garbled version was produced, but still was a clear enough message, however it was incorrect to forward this to Washington first hand as it would reveal that UK is tapping the messages of the neutral countries like the United States.  So a challenge was given to intercept and decode this message forwarded to the German consulate in the Mexican City.

As predicted, it was sent using an older cracked encryption system 13040.  In February, a British agent bribed the worker of the Mexican commercial telegraph company and acquired a copy of the message.  The gamble turned out right it was the same text using older cipher system.  Under the guise that the message was obtained in Mexico by the British authorities the message was directed to the US ambassador in London.  First unsure of its authenticity the Americans released this message to the Associated Press without mentioning the source. Room 40 made a successful turning point in the war.  Perhaps one of the most known examples in history when a decoded message made a major political difference.

Over 200,000 deciphered messages of the German Navy lead to the creation of the Government Code and Cipher School (GC&CS) in 1919. It made way for further enchantments during the Second World War.  The communications intelligence  was made successful by the British Admiralty since it was traditional leading branch of the British military and the signal communications were principal for the navy.  The British naval superiority was essential to secure victory over Germany so breaking their naval codes were the first hand priority during WWI.


[The original and decoded Zimmerman Telegram[7], click to enlarge]

One of the problems for the US during WWI was that their coded messages kept being intercepted and broken by the Germans.  With Germany’s powerful counterintelligence the US faced many situations where their plans where compromised.  One of the situations was the Meuse-Argonne Offensive in 1918 when the US had their codes deciphered and runners for their messages were captured.[9]

German and British Intel also commonly intercepted and decoded each others messages, and the most common messages were made using substitution codes.  The more important messages had improved methods of encryption though.  However Germany was compromised for the rest of the war when their diplomatic and military corps code books fell into the hands of British Intel.[11]  The naval code books were recovered from the wrecked German warships. The Signalbuch der Kaiserlichen Marine (Signal book of the Imperial Navy) was the mainstray of the cipher security of the German naval radio traffic. Three copies of that book – numbers 145, 151, 974 were recovered from the wreaked SMS Magedenburg  near the island of Odensholm (Osmusaar) of the Estonian coast by the end of August 1914. The copy 151 was the only dry one and handed over to the British Admirility Germans created another codebook Flottenfunkspruchbuch (Fleet Radio Communications Book) that was never captured by British or Russians. However the Handelsschiffsverkehrbuch (Commercial Traffic Book)  used for German merchant ships, zeppelins (airships) and U-Boats (submarines) were acquired by the Royal Australian Navy from the German steamer Hobart on October 11 1914. Germans made new book called Allgemeinfunkspruchbuch (General Radio Communicatons Book) that was also acquired on 1916 and 1917 from two zeppelins shot down above the British isles. While the sailors abroud SMS Magdenburg had enough time time to dispose of the codebook, the zeppelin pilots had a time of few seconds in choosing betwen death in flames or suicide by jumping out with no time to think about the cipher security. The most important trophy was the Verkersbuch  (traffic book) the primary German naval cipher system. [15] British MI5 (UK Military Intel) also captured 65 out of 120 spies that Germany sent during the war, which was a record number.[1]  During the war, the membership of the MI5 grew to a total of 884 people.

For the Russian and Austrian counterparts the experience of sending and decoding ciphered messages was with mixed results. The first Russian used cipher system in the battlefield was the ancient Julius Ceasar cipher system. substitutes a group of digits for each letter of the alphabet. This type is solved by knowledge of the relative frequency with which each letter occurs in a given language; in a ciphered German text, for example, the most frequently encountered cipher element – will represent the letter e. Another simple system replaces syllables, endings, prefixes and other word elements with cipher; but these elements also occur with regular frequencies in a given language. Similarly full-word substitutions. More complex systems conceal these frequencies by varying the cipher element substituted, by burying the meaningful ciphers among meaningless ones, by transpositions-“box,” “comb,” “grille, .. “double box”-by re encipherment with additive sequences of meaningless symbols.[13] However, the Austrian intelligence managed to crack the message sent by General Novikov to Warsaw even before the Russians could decipher themselves. As Russians adwanced to Austrian positions at Lodz at Septenber 1914 , at one point they managed to capture the German cipher key and decoded enough messages to know that their own messages are read by the enemy. In result Russians changed their ciphers and left Germans and Austrians in the dark again. But, the defeat was avoided as the Germans Austrians finally deciphered the new Russian ciphrer system and again manged stage a successful counterattack.[13]

Russians wanted to get ahead of the German navy in the Baltic Sea by using the captured German code books. However, on 1917 despite having knowledge of incoming German naval attack the Russian navy was unable to stop the Operation Albion. Germans gathered a large attack force, but aware of the gaps in the operational security and devised a plan to convince the Russian command that the invasion was was headed either from the western coast of the Gulf of Riga into Gulf of Finland . Russians gave warnings days ahead of the actual German minesweeping and landing exercise opperations. Finnally on October 10 after being wrong two times before the Russian intel named October 11 as the German naval attack date. On that day the German navy only started to set sail to the enemy controled waters and the next day when the actual German attack begun the only Russian report was “German C-in-C gave brief orders to IV and III squadron and II reconnaissance groups”. By that the German navy was already actively engaging the Russian navy and chased them into Kronstadt port at the edge of the Gulf of Finland. Thus allowing Germans to take full control over the Baltic Sea.[15]

The Austrians made a ridiculous cipher leak to the opposing Romanians without even noticing it. The Count Czernin the ambassador at Buchraest capitol of Romania was old fashioned cavalier and spent a hour with a lady of his acquaintance  and left his briefcase that contained diplomatic cipher in his cab. As the cab driver also left the cab for some time, the briefcase was suddenly gone. The Count Czernin sent his resignation to Vienna, however the emperor Franz Jospeh saw as regrettable oversight as no real damage was done and the briefcase was returned  by the Romanian police with all of its contents. It never occurred to Vienna that the ciphers are needed to be changed. Then on 1917 when Austrians occupied Bucharest they found photographic negatives of the Count Czernin documents and realized that Romanians and allies had been reading their Foreign Office since the time begun. However, that did not help the Romanians it only made them overconfident and instead their country was overran by the Austrian-German troops who knew their radio codes.[13]


II. Radio Communications

Another method of Communication during WWI was through radio transmissions.  It was called wireless telegraphy.  The WWI era radios were crystal receivers first introduced on beginning of 1901.  Their sound output was far more lover the later day tube radios, making them listenable only with the use of the external earphones.  The frequency range was Low Wave and Medium Wave frequency.  Prior to the 1920’s the frequency range above 2 MHz was considered useless.[12]  First, because of the technical difficulties and common belief that they would probably only travel in straight lines making them useless for long range transmission.  However, as the war broke out it soon turned out that the land telegraph in the battlefield was vulnerable to the artillery fire and enemy diversion.  Worse enough it could be tapped, leaking the codes and orders.  An often used alternative was the telephone, as it was easier to establish the lines among the trenches.  They were deeply buried to avoid discovery and useful for on spot communication and issuing orders.  However, they could also be disrupted and tapped.

A disastrous event took place on the Eastern Front 1914 during the Battle of Tannenberg when Russians were issuing unencrypted messages in Russian believing that Germans could not understand them.[5]  Instead Russian fluent German eavesdroppers intercepted the Russian orders. The Germans received precise information  of Russian positions and attack routes.  The German commander general Erich Ludendorff managed to receive one of the precise military reconnaissance information in the history of military warfare. He reported:  VI [Russian] Corps, on the flank guarding the Narev [2nd] Army would advance through Ortelsburg to Bischofsburg. The Russian XXIII Corps would advance from Neidenburg at Allenstein. Its forward units would be positioned along the Gimmendorf Kurken line.The Russian XV Corps would fight against the German XX Corps on  the line of Gardienne-Michalken. The Russian I Corps-on the left flank of the Narev Army-would move from Mlawa through Soldau-Usdau to Gilgenburg. The Russian Cavalry Crops would stay at Lautenburg and Strasburg.  The I Reserve and XVII Corps will carry the battle with the front to the south, with the VI Russian Corps. Behind it in the area of GerdauenDrengfurt  will be the left flank of the Vilensk [1st] Army. The Russian XXIII Corp’s itself would be positioned along the NadrauPaulsgut line.[14]   In response General Lunderoff devised a plan to leave only two cavalry brigades opposite the 1st Vilensk Army of General Rennenkampf, and to concentrate all the forces of the 8th Army to encircle both flanks of the 2nd Army of General Samsonov. Later the Russian general committed suicide. Similar mistake was later done by the Romanian army on 1916.[13] This unfortunate experience ended up making both sides send encrypted messages even in the telephone lines.  However, the problems caused by the wire communication lead to invest in to wireless telephone or radio.  Nevertheless, the telephone was the most used communication of all during WWI as the radio was often seen as emergency backup in case of line disruption.  This attitude persisted during World War Two. 
An International Signal IP500 Radio used during WWI. From 1917. Made in US by International Signal Company. Made for naval use.
WWI Radio
[Photograph by Howard Stone and Stone Vintage Radio Museum at]

Radio communications proved to be a challenge.  At first it was seen as ineffective the rather massive radio receivers were difficult to use in trenches.  And trying to fine tune the crystals of the receivers to pick up the specific radio signals out of the transmission crowded ether of the trenches.  The signals were even more vulnerable to eavesdropping sparking need for codes and code books.  The most frequently used means of signaling was CW Morse code.  The SSB modulation was patented in 1915 by US transmission theorist John R. Carson and consequently the SSB signals were experimented by the US navy in the very low frequency.[10]

Wireless communication proved to be more useful and vital for the naval and air operations as wired telephones were useless for them.  Morse code sent during the Titanic disaster was not received by almost anyone due to the lack of radio stations abroad the vessels, which lead to compulsory radio station use in the naval and commercial vessels.  Communications were done by using Morse code.  Consequently, the already mentioned Room 40 established a network of the wireless tracking stations around Great Britain codenamed “Y Stations”.  Russia also established wireless tracking or SINGIT stations within the Baltic Sea. The first listening posts were established in September at the Papenhold Naval Station on the island of Saarema the next was established at the Hanko naval base at the Gulf of Finland.  A mojor radio base was built by Russians at the Spithamn (Spithami) peninsula on the Estonian coast 70 km west of Reval (Talinn). The station had 64 meter high wooden antenna mast, wireless telegraph building containing 2 kW sending equipment.[15] The emerging air force also required wireless telegraph as the airships, observation balloons and warplanes required directional and target spotting orders.  However, with this all such antique practices as pigeon post and dog message carriers were used.  Some of their sent coded messages proved to be unbreakable until this day.  Messages were also carried by soldiers such as Gefreiter Adolf Hitler within the German Imperial Army.  WWI brought new kind of army formation – the signal corps, a formation that became an essential part of every army around the world.


III. Numbers Stations

One of the methods people do not suspect messages could have been sent by during WWI was with numbers stations.  The first mention of a numbers station being heard was in the 12 edition of the ENIGMA newsletter[4] and in the Conet Project[3].  This information was from an Austrian radio program called “Kurzwellenpanorama” (Shortwave Panorama).  This would mean numbers stations have been around for 100 years now.  As mentioned above the numbers station that was heard was likely in Morse. 

The individual that the program mentioned was Anton Habsburg, Archduke of Austria[2] who was possibly the first person that had ever heard a numbers station (other than intended recipients).  He was a radio enthusiast and as member of the royal family received rights to construct his own radio receiver.  As commercial radio was scarce those days it serves no wonder as to why a member of the elite society was a radio hobbyist.  His first activities involving listening to numbers stations were in WWI.  The stations he tuned to were FL “Tour Eiffel” from Paris, ICI from Cotona, and FSK from Moscow.[4]  He received about 30 pages of material every day and handed them to the radio operator at the War Office on his way home from school.  The numbers were always checked and found to be correct.

Many people are unaware that numbers stations have been around for this long, and the information on Anton Habsburg confirms, numbers stations were used in World War I.  He was one of the earliest people and possibly the first person to notice a numbers station broadcast.




1.)        Andrew, Christopher, Dr. “MI5 in World War I.” Security Service MI5. Crown
Copyright, n.d. Web. 26 Nov. 2014.

2.)        “Archduke Anton of Austria.” Wikipedia. Wikimedia Foundation, Web. 26 Nov. 2014.

3.)        Fernandez, Akin O. “Numbers Stations: A Begginer’s Guide.” The Conet Project:
Recordings of Shortwave Numbers Stations
(1997): 2+. Iridial.
Iridial-Discs. Web. 26 Nov. 2014.

4.)        “Letters to E.N.I.G.M.A.” ENIGMA Newsletter 12 (Jan. 1997): 29-30. Print.

5.)        Livesey, Anthony. Great Battles of The World War. London. Angus Books. Ltd, p. 30.

6.)         Payne, David, Dr. “Communications on the Western front in the Great War”
                     The Western Front Association. The Western Front Association,
10 Oct. 2008. Web. 26 Nov. 2014.

7.)        “The Zimmermann Telegram.” National Archives and Records
. National Archives and Records
Administration, n.d. Web. 26 Nov. 2014.

8.)        Twigle,Stephen, Hampshire,Evan,Macklin, Evan. British Intelligence.
Secrets, spies and sources.
Kew, National Archives, 2008,
p. 118-120, 244-248,

9.)        Winterman, Denise. “The Original Code Talkers.” BBC News Magazine.
BBC, 18 May 2014. Web. 26 Nov. 2014.

10.)        Weber, Peter. “The History of Single Sideband Modulation.”
DJ4BR. N.p., n.d. Web. 27 Nov. 2014.

11.)        “World War I.” Encyclopedia of Espionage, Intelligence, and Security.
Advameg Inc, n.d. Web. 26 Nov. 2014.

12.)        Олег Головин, Агиляр Хардон, Николай Чистяков, Вольфганг Шварц. Радиосвязь. 
Москва. 2012.  Горячая Линия – Телеком, c. 25-40.
               (Oleg Golovin, Aguilar Hardon, Nikolai Chistyakov, Wolfgang Schwarz. Radio
Moscow. 2012. Hotline – Telecom, p. 25-40.

13)         Wilhelm F. Flicke. The Early Development of Communications Inteligence.

14)         General Major N Batyushkin Cryptography During the World War I A Tsarist Russians View.

15)         Jurve, Ivo. From the Wreckage of SMS Magdenburg to Operation Albion: Russian Early
SIGNIT Efforts on the Baltic. Latvijas Kara Muzeja Gadagrāmata XV
(Latvian War Museum XV Almanac) Latvijas Kara Muzejs. Rīga. 2014.