Ludwig Föppl: A Bavarian Cryptanalyst on the Western Front

Ludwig Föppl: A Bavarian Cryptanalyst on the Western Front


Martin Samuels

(This is an Accepted Manuscript of an article published by Taylor & Francis in Cryptologia on 21 January 2016, available online at:

http://www.tandfonline.com/doi/full/10.1080/01611194.2015.1084960.)

David Kahn has referred to Germany’s codebreaking efforts during the First World War as ‘perhaps one of the greatest missing links in cryptologic history’.1 In 2005, Hilmar-Detlef Brückner drew upon records preserved in the Kriegsarchiv (War Archive) of the Bayerisches Hauptstaatsarchiv (Bavarian Main State Archive) (BHStA-KA) in Munich to begin to fill this gap, examining the efforts of the Bavarian Sixth Army to decrypt Allied naval ciphers.2

One of Brückner’s key discoveries was the central role played by War Volunteer Ludwig Föppl, who ultimately became head of Sixth Army’s Evaluation Office. Since other German cryptanalysts turned to this unit when unable to resolve difficulties in deciphering intercepted messages,3 the implication was that Föppl had risen to become the country’s leading cryptanalyst.

After the war, Föppl became a prominent figure in the German scientific establishment. Elected to the Bavarian Academy of Sciences, he was rector of the Technische Hochschule München (Polytechnical Institute of Munich) between 1947 and 1949. His wartime codebreaking experience, however, was entirely unknown to his subsequent academic colleagues. Even one of the assistants at the university, Dr Friedrich Bauer, who himself later became one of Germany’s leading cryptologists,4 was utterly unaware of his teacher’s involvement in the field.5 Brückner’s discoveries of Föppl’s central role therefore came as a complete surprise.

Föppl’s reticence regarding his wartime activities, reminiscent of the stance later taken by many of the staff at Bletchley Park, meant that, as Greg Goebel wrote, ‘an important chapter in the history of cryptology went to the grave with him’.6 Fortunately, however, it has recently become clear that this was not in fact the case.

Following Föppl’s death in 1976, at the age of 89, some of his papers came into the possession of his fourth child, Liselotte (Elisabeth). In turn, these passed to her youngest child, the author of this article. A recent trawl through this material, which had for some years been stored away in an attic, revealed a folder containing a 206-page typescript labelled ‘Lebenserinnerungen: Ludwig Föppl’. This proved to be a memoir, detailing his life from childhood through until shortly after his retirement in

1 David Kahn, ‘Editor’s Note’ to Hilmar-Detlef Brückner, ‘Germany’s First Cryptanalysis on the

Western Front: Decrypting British and French Naval Ciphers in World War I’, Cryptologia, 29(1) (January 2005) (pp.1-3), p.1. 2 Hilmar-Detlef Brückner, ‘Germany’s First Cryptanalysis on the Western Front: Decrypting British and

French Naval Ciphers in World War I’, Cryptologia, 29(1) (January 2005), pp.1-22. 3 Brückner, ‘Germany’s First Cryptanalysis’, p.19.

4 Friedrich L. Bauer, Decrypted Secrets: Methods and Maxims of Cryptology, 4

th edn (Berlin: Springer,

2007). 5 Brückner, ‘Germany’s First Cryptanalysis’, pp.21-22.

6 Greg Goebel, Codes, Ciphers, & Codebreaking (np: np, 2014) (http://www.vectorsite.net/ttcode.html)

[accessed 18 February 2015], 4.0.

http://www.tandfonline.com/doi/full/10.1080/01611194.2015.1084960

http://www.vectorsite.net/ttcode.html


1954. Three chapters in this unpublished work cover Föppl’s experiences during the First World War. These allow the basic account presented by Brückner to be given greater colour and detail, and further light to be shed on Germany’s codebreaking exploits during the First World War.

Early Years

Carl Ludwig Föppl (known as Ludwig) was born on 27 February 1887 in Leipzig, Saxony.7 His father was August Otto Föppl, a teacher at the city’s Gewerbeschule (Trade School). Through intense study of physics in his spare time, August succeeded in crossing the gulf between the trade schools and the universities, securing the newly-established Professorial Chair of Agricultural Mechanics at the University of Leipzig in 1892. Two years later, in 1894, August was appointed Professor of Mechanics at the Polytechnical Institute of Munich.8

Following completion of his schooling in 1906, Ludwig attended the Polytechnical Institute for two years, studying mechanical engineering: he graduated second in his class of one hundred candidates.9 Ludwig found he had a particular interest in the theoretical aspects of engineering and so his father agreed that he should continue his studies for a year at the University of Göttingen.10 Ludwig returned to Munich for the 1909/10 academic year, in order to secure a certificate as a schoolteacher of mathematics and physics. This gave him a safety net, should his ambition of an academic career not bear fruit.11 He then went back to Göttingen in 1910, gaining his doctorate in mathematics in 1912. Ludwig remained in the city for a further two years, working as assistant to Professor Felix Klein,12 a leading expert on the interface between mathematics and physics, with a special focus on mechanics.

In March 1914, Ludwig completed his mathematics Habilitation13 (broadly equivalent to the present-day completion of a period of post-doctoral research, and a prerequisite for future promotion to a professorship). He began teaching as a Privatdozent (independent lecturer) at the University of Würzburg. There, he worked especially in the prestigious Physics Institute, which was at that time headed by Wilhelm Wien, who had won the 1911 Nobel Prize for Physics.14 Wien’s elder daughter, Gerda, would in due course become Föppl’s second wife.

By the summer of 1914, therefore, Ludwig had mounted the first rungs in his desired profession as an academic. As a teacher in one of the most respected institutes in his field, he was well placed for a successful career. But world events meant his life took a different turn.

7 Ludwig Föppl, Lebenserinnerungen, p.1.

8 August Föppl, Lebenserinnerungen: Rückblick auf meine Lehr- und Aufstiegjahre (Munich:

Oldenbourg, 1925), pp.112-146, and Gunhard AE Oravas, ‘Introduction’, in August Föppl and Ludwig Föppl, Drang und Zwang: Eine höhere Festigkeitslehre für Ingenieure, vol.1, 3

rd edn (1941) (New

York, NY: Johnson, 1969), pp.vii-xxix (pp.xiii-xx). 9 Föppl, Lebenserinnerungen, pp.35-37.

10 Föppl, Lebenserinnerungen, pp.41-42.

11 Föppl, Lebenserinnerungen, p.55.

12 Föppl, Lebenserinnerungen, pp.68-86.




Enlistment and Arrival in France

With the outbreak of the First World War in August 1914, Föppl was determined to experience life at the Front as soon as possible.15

Given his social background, it might be expected that this ambition would have been easily achieved. As Alexander Watson has shown, a substantial proportion of the Offiziere der Reserve (reserve officers) came from the upper middle classes. These individuals had undergone a year’s training as Einjährig-Freiwillige (One-Year Volunteers), for which privilege they paid their own costs.16 The high status of a commission in the reserve meant that there was no shortage of volunteers: sixty-four thousand applicants in 1912 alone. After further training in the two years following their period of service with the standing army, only a small proportion successfully achieved the high standards required to secure a coveted commission as a reserve officer. The majority were retained as NCOs in the reserve.17

In fact, Föppl’s route into the army was less straightforward. Despite the steady growth in the size of the army in the years prior to 1914, fewer than half of the young men in each annual recruit contingent were required for military service.18 Indeed, it is likely that Föppl was never even considered for conscription during the eligible period (when he was aged between 20 and 22, in 1907 to 1909), since students received an exemption from service, in order to continue their studies.19

In wanting to enlist once war broke out, despite his lack of previous military experience, Föppl appears to have been entirely typical of his peers. As Watson has shown, although academics and professionals together comprised just 0.5% of the working population, they supplied 6.75% of the wartime volunteers, half of whom joined the colours during the first month of the war.20 Föppl was also typical in his motivation. His memoirs describe how, following the assignation of Archduke Franz Ferdinand in June, and especially in late July after the Austro-Hungarian ultimatum, the atmosphere was like that of an ‘approaching thunderstorm’. He recorded how everyone was hoping a wise compromise would counteract the ‘senseless war frenzy’ that ultimately tumbled Europe into conflict.21 The evidence suggests that, when war did break out, most of his peers were driven to enlist by a sense of patriotic duty. This may have been coupled with feelings of peer pressure. Equally, given that some 40% of the country’s students enlisted during 1914, Föppl might also have been influenced by the fact that there were few people left for him to teach.22

15

Föppl, Lebenserinnerungen, p.95. 16

Alexander Watson, ‘Junior Officership in the German Army During the Great War, 1914-1918’, War in History, 14(4) (2007), 428-453 (p.432). 17

Martin Samuels, Command or Control? Command, Training and Tactics in the British and German Armies, 1888-1918 (London: Cass, 1995), p.82. 18

German Army Handbook (April 1918, repr. London: Arms & Armour, 1977), pp.9-11. 19

Alex Watson, ‘”For Kaiser and Reich”: The Identify and Fate of the German Volunteers, 1914-1918’, War in History, 12(1) (2005), 44-74 (p.53. 20

Watson, ‘Kaiser and Reich’, pp.49-53. 21

Föppl, Lebenserinnerungen, pp.93-94. Of course, these word were written not only after Germany had lost the war, but following the catastrophic defeat of 1945. There is, however, little reason to doubt the sentiments expressed. 22

Watson, ‘Kaiser and Reich’, pp.51 & 58-62.


Having decided he should enlist, Föppl discovered actually doing so was quite difficult. He went to the barracks of the artillery regiments based in Munich, but found them already overflowing with volunteers. He returned to Würzburg, only to be told by the artillery regiment there that ‘any further application within half a year would be pointless’. Not willing to take no for an answer, Föppl returned to Munich in early September, determined to try his luck with the reserve infantry regiment then based in the Turkish School.23 On the way there, he ran into a friend of his parents, Professor Peter Vogel, who taught mathematics at the Munich Kriegsschule (War School, which trained aspirant officers) and Kriegsakademie (War Academy, which trained staff officers). Vogel suggested that, rather than join the infantry, Föppl could offer greater service in the wireless telegraphy service, and provided him with an introduction to a colonel in the Bavarian Ministry of War. Föppl immediately went to the Ministry and presented Vogel’s card. It did the trick: the colonel promptly instructed Föppl to report the following day to the barracks of the wireless telegraphy company.24 Thus, on 10 September 1914, he finally achieved his aim and enlisted as a Kriegsfreiwillige (War Volunteer) in the Funker-Ersatz-Kompagnie (Wireless Telegraphy Replacement Company).25

Föppl underwent three months of training with his unit in Munich. His platoon included several other war volunteers, but at the age of 27 he was much the oldest recruit. In his memoirs, Föppl made clear that he was not a natural soldier and so found the training strenuous: marching ‘was not my strength’, at target practice he was no better than average, and riding exercise gave him ‘some sour hours’. Luckily, he was good at running and at climbing over obstacles, so retained some standing with his peers. With regard to Morse code, perhaps the key task of a wireless telegraphy operator, however, Föppl found he was already too old to pick this up quickly: he could manage only eighty characters per minute,26 while others achieved more than a hundred.27 Nonetheless, he passed his training successfully.

In early December, a request was received from the Wireless Telegraphy Command of the Bavarian Sixth Army for an officer and eight men, at least some of whom could speak English, to be despatched to La Madeleine, a suburb of the city of Lille. Föppl put himself forward, although he had only limited ability to read English, and could neither speak the language nor understand it when spoken. To his delight, he was chosen nonetheless, along with two other war volunteers. On arrival in La Madeline, however, these three were greeted with dismay by a captain in the unit, who

23

This was a nondenominational school, opened in 1874, which taught boys and girls of all faiths, in contrast to the more common separation of schools by religious affiliation. The building was designed by the well-known architect, August von Voigt. (http://www.tuerkenschule.de/geschichte.html) [accessed 23 July 2015]. 24

Föppl, Lebenserinnerungen, pp.95-96. 25

Kriegsstammrolle 17473: Armee-Funker Abteilung 6, vol.1 (BHStA-KA). 26

In the English-speaking world, it is more common to measure speed in words per minute, where a ‘word’ is deemed to have five characters of a form typical of natural language words, such as PARIS, or else form a ‘code group’ of complex letters, such as CODEX. The US Federal Communications Commission requires applicants for a Radiotelegraph Operator Licence to pass a twenty word per minute plain text test, equivalent to the hundred characters per minute that Föppl recorded as the standard achieved by his peers. If instead compared with the sixteen word per minute code test, Föppl’s peers would have been performing significantly above the FCC standard, while even Föppl himself would have met the standard. (https://en.wikipedia.org/wiki/Morse_code) [accessed 23 July 2015]. 27

Föppl, Lebenserinnerungen, pp.96-97.

http://www.tuerkenschule.de/geschichte.html

https://en.wikipedia.org/wiki/Morse_code


exclaimed, ‘What am I supposed to do with these stinkers?’ Fortunately, the captain’s fears were calmed by the officer in charge of the detachment, who dissuaded him from simply sending Föppl and his two comrades straight back to Munich. Instead, they were posted to the station in Roubaix, a town 8 km from La Madeleine and 20 km behind the front line.

Föppl arrived in Roubaix on 15 December 1914.28 The unit’s task was to listen to enemy wireless communications, not only those few signals emanating from the British Expeditionary Force facing Sixth Army, but more importantly, those broadcast by the Royal Navy in the English Channel. Although the occasional signal was sent in clear, most were encrypted. Since there was believed to be no means by which these could be deciphered, they were simply transcribed, organised by sending station, and then put to one side.

Given his limited expertise with Morse code, Föppl could not take a turn with the others in transcribing the British messages. Since he could speak a little French, he was instead employed as a Küchenjunge (kitchen boy). Each day, he would prepare a shopping list with the nominatively-determined head cook, Gefreiter (Corporal) Fleischmann, and then proceed to the local market, which was still operated by the local population. Mainly women and old men, the stallholders treated him well and soon nicknamed him ‘Doctor’ – but only because of his glasses and full beard!

Although Föppl enjoyed his daily shopping excursions, this was hardly what he had intended when he enlisted. He therefore sought a more fulfilling employment for his abilities.29

Unexpected Codebreaker

Each day, the listening station at Roubaix intercepted dozens of British wireless telegraphy signals. Sending and receiving stations could be identified, but the content of the messages themselves was impenetrable. As has been noted, they were therefore merely recorded, organised by sender and receiver, and put to one side. By early 1915, there were ‘mountains’ of these messages. Having little else with which to occupy his mind, Föppl sought permission from the Oberleutnant (lieutenant) to spend some time attempting to decipher them. This officer, though doubting the chances of success, agreed that he could devote his afternoons to this endeavour. The method of analysis presented in Föppl’s memoirs is somewhat different from the account presented by Brückner.30

Föppl began by attempting to identify which signals had been enciphered using the same key. He did this by looking out for common sequences of characters in the messages. His search was made relatively straightforward by the fact that the messages were transmitted in sets of five letters, with a brief pause between each set. These were transcribed by the Roubaix listeners on squared paper, such that each message was presented as a series of columns of letters. As a result, standard sequences of characters stood out readily.

28

Kriegsstammrolle 17534: Funker Tr. Überw. Roubaix, vol.1 (BHStA-KA). 29


Brückner, ‘Germany’s First Cryptanalysis’, pp.8-9.


Föppl focused on sequences of four or more characters. Where such a sequence appeared more than once in a single message, or in several different signals, he took this to indicate that they had been enciphered with the same key. It took him only a short time to sort the messages from the previous few days into several groups. He then focused on the group that seemed to him the easiest to analyse, as it contained the largest number of messages and the most repetitions of common sequences. Föppl recorded the frequency with which each letter appeared in these messages, and then compared this against the equivalent statistics for a plain text English document. The coincidence was so great that he was instantly able to determine the key. Since this key was still in use by the British, the Roubaix station would at once be able to start reading new signals as they were received.31 Although this means of breaking a cipher had been discovered long before, it appears Föppl was entirely unaware of this and proceeded purely on the basis of his own logical deductions.

When Föppl showed his lieutenant the first decryptions that evening, he was met with astonishment – everyone had been convinced the British code was unbreakable. Fortunately, the lieutenant was an engineer in civilian life, so was readily able to comprehend the systematic techniques Föppl had used. The news spread like wildfire. Even the captain from La Madeleine, who had been so contemptuous of the three war volunteers only a few weeks before, came personally to Roubaix to learn more about Föppl’s breakthrough.

The men of the station suddenly felt that their work had a genuine purpose and redoubled their listening efforts, bombarding Föppl with new signals, in the hope that he would be able to identify further keys. Föppl himself was not only relieved of his ‘kitchen boy’ duties, in order to focus on his decryption work, but also received an assistant. To cope with the demands of this growing workload, the station moved into larger premises and further men were summoned from Munich – and, this time, there was a special request for war volunteers.32

The majority of the decrypted messages related to British minesweeping operations in the English Channel. The listeners realised that the level of signal traffic increased significantly when German U-boats were sighted, as the minesweepers signalled the position of the enemy vessel. Other messages reported the location of the lanes that had been cleared of mines.

Föppl recognised that the key he had discovered was an especially simple one, which he subsequently learned was termed a ‘Caesar’.33 Based on the records of the Roubaix station, Brückner was able to demonstrate that the Royal Navy was, in fact, using a more advanced variant of the basic Caesar cipher, called a Gronsfeld cipher, after its seventeenth century inventor.34 Nonetheless, the cipher remained relatively uncomplicated. Föppl suggested that this level of simplicity was necessary, as it enabled messages to be quickly and easily enciphered by ordinary sailors. Even

31



Simon Singh, The Code Book: The Secret History of Codes & Code-breaking (London: Fourth Estate, 2000), pp.9-14. 34



though the key was changed every few weeks, the simplicity of the cipher meant that each new key could be broken within a single day.

The ability to read many of these low-level messages allowed the Germans to gain an insight into both the standard forms of expression used by the Royal Navy operators and the typical subject matter of signals. The stereotyped nature of many of the signals meant that the Roubaix listeners discovered they could often predict the nature of a message, even before it had been decrypted. This standard format for messages proved of valuable assistance as Föppl sought to break each new key.35

Having mastered the basic cipher used by the minesweepers, Föppl next turned his attention to other elements of the British wireless traffic. One such was the daily message broadcast by the individual whom Föppl referred to as ‘the Admiral of Devonport’ – presumably Vice-Admiral Sir George Egerton, Commander-in-Chief, Plymouth. This lengthy telegram gave details of all the lanes that had been swept by the minesweepers, so ships passing through the area could follow these safely. Although the cipher was different from that used by the minesweepers, and changed every fortnight, it proved especially simple to decipher: in a classic example of poor operator practice providing a critical weakness that could be exploited by the cryptanalyst, every message was signed ‘Admiral of Devonport’, thereby giving an instant insight to the key.

Föppl also described in his memoirs how he broke the Allied Fleet Code. Based on completely different principles from the ciphers used by the minesweepers, it was long considered unbreakable. Understandably, therefore, Föppl considered cracking this code his greatest achievement in cryptanalysis. Although Brückner was able to report that the code had been solved, his sources gave little detail as to how this had been done.36

The Fleet Code was constructed on an entirely different basis from the minesweeper messages. Rather than using a letter-substitution cipher, it employed a three-letter code to represent whole words. As Föppl recorded in his memoirs, this gave a total of 15,625 possible letter combinations: far too many to allow the attributions to be determined.

Föppl then made two breakthroughs. First, he realised that the same codebook was used for both encoding and decoding messages. This meant that the three-letter groups must be in the same alphabetical order as the plaintext words they represented. In addition, the number of combinations actually used was far smaller than the theoretical maximum, given the constrained list of terms required for maritime affairs. In addition, some combinations were required for encipherment of individual letters, for use for proper names and the like. Second, Föppl used his familiarity with the style of language used by Royal Navy operators, gained from the messages previously decrypted, to connect certain letter combinations with particular words. The first word so decoded was ‘submarine’, which appeared very frequently. As each letter combination was identified, the scope of the remaining combinations was reduced, making it ever easier to assign words to them. By June 1915, the task

35


Brückner, ‘Germany’s First Cryptanalysis’, p.11.


was largely complete. Such was the value of the messages that could now be read that the German navy assigned a Kapitänleutnant (lieutenant commander) to Roubaix, with whom Föppl worked on a daily basis.37

Records examined by Brückner demonstrated that the German navy considered this new source of intelligence to be of great importance. From the end of July 1915, copies of the daily reports prepared by Föppl and Lieutenant Commander Martin Braune were sent directly to a range of naval headquarters, including those of the High Seas Fleet, the Admiralty Staff in Berlin, and the commander of U-boats. On 30 October 1915, the commander of the High Seas Fleet, Admiral von Pohl, requested that his personal thanks be passed to the team at Roubaix, noting ‘They have proved to be a great help for our submarine and Zeppelin missions.’38

Figure 1: Leutnant Ludwig Föppl, August 1918 (Author’s collection)

Life as a Codebreaker

Föppl’s success as a codebreaker meant that he was given far greater freedom and flexibility than the norm, his commanders recognising his work required space for thinking. As a result, Föppl was not required to adhere to the usual working hours: for example, he was able to go out for a walk at any time of the day, should he feel

37




the need. He found the knowledge that he could exercise such freedom, if he wished to do so, was sufficient, however, and so he took only limited advantage of it in practice.

Although still only a junior NCO, Föppl often spent his evenings with the new commander of the Roubaix station, Hauptmann Prügel, playing chess or in conversation. Despite recognising Föppl’s essentially unmilitary character, Prügel and the other officers were determined that his achievements should be recognised by the army.

One means by which this was achieved was through the award of decorations. On 4 July 1915, Föppl was awarded the Iron Cross, Second Class. This was followed by the Iron Cross, First Class on 16 April 1916.39 At that point in the war, this medal was still a rare award: the only other member of his unit who had received it was the Hauptmann in command and so the whole company paraded for the ceremony. Föppl noted that, thereafter, he was treated with particular respect, even by the local French civilians.40 The Iron Cross was, of course, a Prussian medal. Föppl was also recognised by his own country, receiving the Bavarian Militärverdienstorden (Military Merit Order). First, the Fourth Class with Swords,41 and then, on 12 September 1916, the Third Class with Swords.42 Although the first of these awards was common (24,141 were granted during the war), the second was much rarer: only 834 were issued (2083 of all variants of the Third Class).43

Figure 2: Ludwig Föppl’s Medals

39

Kriegsstammrolle 17473. 40


Kriegsstammrolle 17191: Armee Nachrichten Kommandeur 6 vol.2 (BHStA-KA). 42

Kriegsstammrolle 17473 43

Georg Schreiber, Die Bayerischen Orden und Ehrenzeichen (Munich: Prestel, 1964), and Arnhard Graf Klenau, Orden in Deutschland und Österreich, vol.2 (Offenbach: Graf Klenau, 2008), pp.128-137.


(Author’s collection)

In his memoirs, Föppl noted that, in his experience, such decorations had both a positive and a negative impact. Those who were so honoured tended to feel that the award was justified and they, and others similarly recognised, were encouraged to yet greater efforts. Less positively, however, he found that those whose achievements were not so acknowledged could easily fall into envy and dissatisfaction. Nonetheless, Föppl felt that such awards were appropriate in a military context, where the recipients had risked their lives. By contrast, he regarded the practice in civilian life as pointless, especially in a democratic state. In such situations, he believed that success should be its own reward, without the need for this to be highlighted with medals and titles.44 That said, the author has in his possession the decorations awarded to Föppl to mark his election into the Bavarian and German Academies of Sciences, and Föppl had also been in little physical danger during his service as a cryptanalyst.

Figure 3: Ludwig Föppl’s Militärverdienstorden (Military Merit Order) – Third Class with Swords (Author’s collection)

The other means by which the army showed its recognition of Föppl’s efforts was by advancing him in military rank. As Brückner45 and his unit personnel files46 recorded, he was promoted to corporal on 24 April 1915, identified as an aspirant officer on 30 September 1915, and then raised to the rank of Vizwachtmeister (sergeant) on 9

44


Brückner, ‘Germany’s First Cryptanalysis’, pp.13-14 & 20. 46

Kriegsrangliste 17617: Nachrichten Ersatz Abteilung (BHStA-KA).


January 1916. He now sat with the officers during meal times, which, he recorded, brought benefits, but also had its (unspecified) inconveniences.47

Having been identified as an aspirant officer, it was necessary for Föppl to undertake the proper training. This would normally have involved his being posted back to the Ersatz company in Munich for several months. The captain in command of the unit in Roubaix, however, declared that Föppl could not be spared and, instead, took it upon himself to deliver the necessary training. From his memoirs, this appears to have involved a combination of theoretical education, delivered in excellent style by Oberleutnant Kraft, and frequent riding lessons!48 The success of this unorthodox approach was shown when Föppl was appointed a lieutenant in the reserve ohne Patent (without commission) on 14 July 1916. Then, in August 1918, that rank was converted to a full commission in the regular army, with seniority backdated by four years to 9 August 1914.49 Of course, despite being perhaps Bavaria’s leading codebreaker, Föppl was still only a lieutenant, an example of the army’s famous parsimony with rank.

Föppl’s promotions and decorations allowed him to build a small team of likeminded men around him, several of whom were, like himself, war volunteers:50

Dr Hans Rau, a lecturer in physics from the University of Würzburg and, as such, a former colleague of Föppl’s. Five years older than Föppl, Rau too proved to be an excellent cryptanalyst. In due course, he took over command of a listening station in the vicinity of Douai, where he had some success deciphering the codes used by the BEF, for which he was awarded the Iron Cross, First Class.

Dr Wilhelm Lenz, a lecturer in physics at the University of Munich and student of Arnold Sommerfeld, who had been personally selected by Wilhelm Röntgen to become director of the prestigious Institute for Theoretical Physics.

Dr Engelhard, an assistant in mathematics at the University of Würzburg, known as ‘lange Engelhard’ due to his being 1.9m tall.

Sergeant-Major Abrahamson, a respected lawyer from Berlin. Twenty years older than Föppl and so nicknamed the ‘Landsturmmann’ (militia man), Abrahamson retained his legal outlook throughout his military service. Föppl recorded that, when the unit discussed options for improving the effectiveness of their operations, after a while Abrahamson would declare it necessary for the advantages and disadvantages of each option to be captured on paper. He would promptly pace up and down the room, dictating while Föppl acted as his stenographer.

More widely, Föppl found that he was able to use the importance of the decryption work as a means to rescue bright young men from the fighting. Since only the initial transcription of the signals required knowledge of Morse code, the men undertaking

47



Kriegsrangliste 17609: Nachrichten Ersatz Abteilung 1, vol.1 (BHStA-KA). 50



the decipherment no longer needed this specific skill, so the net could be thrown much more broadly.

Föppl highlighted the importance of this by giving an account of one such soldier. He had been alerted by a former colleague from Göttingen, Richard Courant, that one of the most gifted mathematics students the latter had ever taught, Leutnant Herkner, was serving with the infantry at the Front in the vicinity of Cambrai. Föppl immediately secured orders for Herkner to be transferred to Roubaix, only to discover he had been killed in action a few days earlier.51

Similarly, Föppl recorded his delight at one day being unexpectedly visited by a dear old friend of his, Eugen Gyssling. Gyssling, a Marineleutnant (Sub-Lieutenant), had been aboard SMS Emden, a light cruiser, during its daring operations as a raider in the Indian Ocean. On 9 November 1914, he had been one of three officers leading a landing party to destroy a British wireless station when the Emden was engaged and disabled by HMAS Sydney. Boldly, the landing party had commandeered a schooner and sailed across the ocean to Yemen. They then travelled overland to Constantinople, where they reported for duty to the German naval forces in the city.52 Gyssling was in the area of Roubaix as he was visiting his father, who was Generalleutnant der Etappe (Major-General of the Rear Echelon) for Sixth Army.53 Following the visit, Gyssling joined the crew of U-50, which was subsequently lost with all hands.54

In contrast to the intense danger experienced by these friends and peers, Föppl recorded only a single occasion when he was himself exposed to risk. Travelling in an open-topped car with his captain, they spotted two Allied aeroplanes high above them. Since the enemy pilots were known for the assiduousness of their shooting, the driver immediately put his foot down and the vehicle sped towards the safety of a nearby wood. All was well – except that the wind resulting from this sudden manoeuvre had blown off the captain’s cap. An officer without his hat was unthinkable, so Föppl ordered the driver to stop the car, leaped out and ran back to retrieve the offending item of headgear! Luckily, the Allied pilots did not see them and so they did not come under attack.55

By the end of the war, Föppl was head of Sixth Army’s Evaluation Office,56 based first in Lille and then Tournai. There is a note of satisfaction in his memoirs, where he noted that he had ‘eine recht beträchtliche Zahl von Mitarbeitern’ (a fairly significant number of people) under his command, and that on his desk stood a telephone that linked him directly to the intelligence officer at Sixth Army headquarters, with whom he spoke daily.57

In late July 1918, Föppl took a period of leave, during which time he became engaged to Friederike Pühn, whose father, Ernst, was a bank director. On his return,

51


Dan van der Vat, Gentlemen of War: The Amazing Story of Captain Karl von Müller and the SMS Emden (New York, NY: Morrow, 1984), pp.170-176. 53


van der Vat, Gentlemen of War, p.194. 55


Brückner, ‘Germany’s First Cryptanalysis’, p.19. 57

Föppl, Lebenserinnerungen, p.117.


he noted a pervasive loss of confidence among the troops, resulting from the arrival of the Americans having shifted the longstanding balance of forces along the Front. Following the long and painful retreat over the last months of the war, Föppl found himself back in Munich on 30 November 1918, where he was demobilised.58

Recalled to Service

Brückner noted that Föppl, as one of the country’s leading cryptanalysts of the First World War, was recalled to service in 1938 and then again in late 1939, but was soon discharged ‘for reasons unknown’ – he speculated that Föppl’s research at the university in Munich was considered more important than any contribution he might make as a codebreaker.59 Once again, Föppl’s memoirs clarify events.

In March 1938, while skiing in the Bavarian Alps with his family, Föppl received a telegram instructing him to report to Army Headquarters in Berlin in connection with the occupation of Austria. He recorded that he received these orders ‘with a heavy heart’, as he was utterly against the annexation. On arrival in Berlin, he discovered that no-one knew what to do with him. His discomfort was increased by the fact that he had no uniform, so remained in civilian clothes. Although this was noted with displeasure by the staff at Army Headquarters, it was also recognised that there would be something unfitting in requiring Föppl to wear the uniform appropriate to his military rank as an Oberleutnant (lieutenant), given that he was fifty-one years old and had been a professor for the past eighteen years.

In the end, a major took pity on him, gave him a map showing the locations of the Czechoslovakian radio stations and sent him to Vienna to report to the German wireless company based there. Having found his destination only after some difficulty, Föppl was greeted with astonishment at his having been entrusted with a military task while still in civilian clothes. Fortunately, the commander of the wireless company, Hauptmann Kleinschrodt, knew him, as he had studied at the Polytechnical Institute, and so the situation was resolved. There remained, however, the question of how he was to be employed. In the end, it was agreed that Föppl should be asked to make contact with the staff at the Vienna Technische Hochschule. Having visited the Rector of the Institute, he was invited to attend a meeting of its Senate. He found himself inundated with questions about the implications of the Anschluβ for academic freedom, especially whether all professors would be required to join the Nazi Party if they wished to retain their positions – he responded that this would not be necessary, using himself as an example. After a week, it was clear that there was no further military need for him, so he was released from service and sent back home to Munich.60

58


Brückner, ‘Germany’s First Cryptanalysis’, p.20. 60



Figure 4: Professor Ludwig Föppl (Author’s collection)

Having continued with his academic interests during the seventeen months following this demobilisation, on 25 August 1939, Föppl again received a telegram ordering him to report to Army Headquarters in Berlin. He recorded that ‘a deep depression fell over the entire family’. Föppl’s mood can hardly have been improved by the fact that he arrived in Berlin on 27 August – his (third) wife’s birthday and, as such, a date normally treated by the family as the high point of the summer holidays.61

Föppl was assigned to the Evaluation Office, a large unit with many teams within it, which had been built up over a number of years and contained a number of skilled cryptanalysts. They were well aware of Föppl’s work during the First World War, so he was warmly greeted and the work of several of the teams was explained to him. He was assigned an office and immediately began work, trying to regain the ways of thinking of a cryptanalyst after twenty-one years absence from the task. He began by trying his hand at cracking a number of enciphered messages that others had already attempted without success: he recorded in his memoirs that his efforts were equally fruitless.

Living like a student, sleeping in a bunk, trapped in an office all day, sustained by only the simplest of meals, Föppl found his new existence a severe trial, used as he was over decades to the complete control over his own life he had previously enjoyed by virtue of his status as a full professor. Discontented with both his task at Army Headquarters and with the campaign against Poland being directed from there, he successfully sought to be posted to a newly established decryption role with one of the western army headquarters, based in Frankfurt-am-Main. Life there was much

61

Föppl, Lebenserinnerungen, p.166.


more comfortable – he rented a room with a friendly married couple, whose apartment was a pleasant twenty-minute walk to his office, got on well with his colleagues, and ate his meals at a nearby hotel. These improved conditions clearly had a positive impact on his work, as Föppl recorded that he secured a significant decryption success. This was highly recognised, though he gave no details of its nature in his memoirs. Perhaps his disapproval of the political context meant that the achievement gave him little pleasure.

Nonetheless, despite the relative comfort of his life in Frankfurt, Föppl missed his family. He therefore engineered that the Polytechnical Institute in Munich formally requested that he be released, in order to return to his teaching duties. This request was approved by Army Headquarters and he was discharged on 20 January 1940.62 His military service, and hence his work as a cryptanalyst, was at an end.

Cryptanalysis and the German Army

It is apparent, both from Föppl’s own narrative and from the official material examined by Brückner, that the codebreaking activities of the Bavarian Sixth Army during the First World War were both militarily significant in themselves and also represented a major achievement in cryptanalysis. Germany had entered the war expecting it to be brought to a rapid conclusion through decisive manoeuvre on the battlefield. Since the fighting would largely take place on French soil, the retreating forces would have the advantage of their own existing landline system for communications, meaning there would be little wireless traffic for the advancing Germans to intercept, coded or not.63 There seems, therefore, to have been minimal effort made before the war to establish an infrastructure to decipher what messages were intercepted.64 This was reflected in the primitive arrangements that Föppl found when he arrived in Roubaix.

What stands out from Föppl’s account, however, is the surprisingly unorganised approach that appears to have typified the German Army’s use of its war volunteers. It seems almost beyond belief that Föppl, a lecturer at one of the most prestigious physics institutes in the world, was at first employed merely on errands to the local produce market. Similarly, the gathering of a number of his peers and former colleagues in the cryptanalysis section seems to have been driven by Föppl himself, though with official support, rather than being the product of a planned allocation of expert manpower.

Brückner suggested that the cryptanalysis successes achieved by Föppl and his colleagues were in part made possible because the junior officers who at first commanded them recognised that they were engaged in highly technical work and so gave them the freedom required to enable them to apply novel solutions to the problems of deciphering enemy messages. The successes so achieved then gave them the standing that allowed them thereafter to operate with minimal interference from the German Army’s formal structures.65 Yet the German Army was no stranger to highly technical work even outside those areas most immediately associated with

62


Singh, Code Book, pp.106-107. 64

Patrick Beesley, Room 40: British Naval Intelligence 1914-18 (London: Hamilton, 1982), p.3. 65

Brückner, ‘Germany’s First Cryptanalysis’, p.21.


warfare, such as tactics and weapons design. As Arden Bucholz showed, the German General Staff had mastered the technical capabilities required to resolve the mobilisation and deployment of armies comprising millions of men, along with their horses, weapons, and supplies, which represented ‘the largest and most significant management and control problem in the nineteenth-century world’.66 Yet it failed to recognise the need for cryptanalysis.

This position may instructively be contrasted with the course of events ‘on the other side of the hill’, in Room 40 of the British Naval Intelligence Division. Like the Germans, the Royal Navy had no codebreaking structures in place at the outbreak of war in August 1914. Fortuitously, however, the Director of Naval Education, Sir Alfred Ewing, had previously been Professor of Mechanical Engineering at Cambridge University67 and had expressed an interest in ciphers. He was accordingly assigned the task of decrypting the German messages being intercepted by the British. Ewing at first called upon staff from the Royal Naval Colleges at Osborne and Dartmouth, who had limited employment at the time, as their senior cadets had been mobilised. The pool of cryptanalysts was then expanded through judicious recruitment of linguists and mathematicians.68 Their task was made immeasurably easier than that faced by Föppl and his colleagues by the capture by the Allies of all three of the main German naval codebooks during the early months of the war.69 Nonetheless, it seems clear that the British had very quickly realised the importance of securing civilians with relevant skills in order to make a concerted effort at deciphering the German traffic. By contrast, the German effort seems to have been driven almost by chance through Föppl’s initial breakthrough, which was inspired simply by his own boredom.

This picture of an unorganised approach in the German Army was repeated two decades later, when Germany was about to go to war again. The importance of cryptanalysis had been recognised between the wars, and a substantial decipherment capacity developed within Army Headquarters. However, the fact that Föppl’s mobilisation in March 1938 appears to have come as something of a surprise to the cryptanalysis unit’s members suggests that an element of improvisation remained, though this appears to have been resolved by the time he was mobilised again the following year.

It may be suggested that the treatment experienced by Föppl and his fellow war volunteers in the early months of the war reflected a wider failing in the German Army’s attitude to this sudden influx of men who had not been educated in its military ways through the conventional route of a period of conscription. The reaction of the captain at La Madeline in December 1914, who reacted with dismay when confronted by three war volunteers,70 was perhaps typical. As Watson has demonstrated, 40% of Germany’s students and 50% of its Gymnasiasten (high school pupils) enlisted during 1914 – sixty thousand enthusiastic and well-educated young men.71 A substantial proportion of these and the other war volunteers were

66

Arden Bucholz, Moltke, Schlieffen, and Prussian War Planning (New York, NY: Berg, 1991), p.12. 67

Given their shared academic interests, it is possible that Ewing knew Föppl or his father, or was at least familiar with their publications. 68

Beesley, Room 40, pp.8-12. 69

Beesley, Room 40, pp.3-7. 70


Watson, ‘Kaiser and Reich’, p.51.


hastily formed into six new corps and, after only two months of inadequate training, declared fit for action. Within a fortnight, many of the units had lost half their infantry fighting against the British at Ypres.72 Even after this, war volunteers became ‘the secretly most despised and hated creature of the front’, which had obvious impact on their chances of survival.73

Watson noted that the war volunteers whose lives were so negligently thrown away in 1914 could have become the junior leaders so needed by the German Army later in the war.74 This is, of course, what the British Army succeeded in doing. By March 1915, commissions had been awarded to over twenty thousand young men who had obtained some previous military experience in the Officers Training Corps, established in 1907 with arms in both the universities and many public schools. Many others, who had no prior training, were also given commissions,75 such that fully seven thousand men who had enlisted into the ranks of the University and Public Schools (98th Infantry) Brigade had received commissions by April 1916.76 These young men were of very similar background to the students and high school pupils who volunteered at the same time in Germany.

In summary, therefore, despite the fact that the German Army was probably the most advanced in the world in 1914, in terms of managerial and technical expertise, as demonstrated by the smooth mobilisation and deployment of its vast army in August 1914, it seems to have been blind both to the need for cryptanalysis and to the potential offered by the tens of thousands of educated young men who volunteered for service in the opening weeks of the war. By contrast, while Britain’s preparations for war on the European scale were in many ways grossly deficient, the speed with which the Royal Navy established a cryptanalysis service, largely staffed by civilians, and the readiness of the army to grant commissions to tens of thousands of young men from very similar backgrounds to those whose lives were squandered by the German Army at Ypres, suggest a system that was more open to the innovation and ideas from outside the traditional military sphere.

72

Watson, ‘Kaiser and Reich’, pp.65-66. 73

Watson, ‘Kaiser and Reich’, p.69. 74

Watson, ‘Kaiser and Reich’, p.71. 75

Keith Simpson, ‘The Officers’, in A Nation in Arms: A Social Study of the British Army in the First World War, ed. by Ian F.W. Beckett and Keith Simpson (Manchester: Manchester University, 1985), pp.63-98 (pp.72-73) 76

Peter Simkins, Kitchener’s Army: The Raising of the New Armies 1914-16 (Manchester: Manchester University, 1988), pp.224-225.

Ludwig Föppl: A Bavarian Cryptanalyst on the Western Front

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