Tuesday, July 26, 2011

German Signals Intelligence and the battle of France

During the Second World war all sides read some enemy codes.The achievements of anglo-american codebreakers are well known thanks to books like ''The Ultra secret'' , ''Ultra goes to war '' , ''Top secret Ultra'' etc... The Polish codebreakers ,Turing ,Friedman are mentioned in popular history books.However there is no similar understanding of the role and achievements of the German codebreakers.

One area where good information is lacking is the battle of France.How did the German army manage to defeat numerically superior forces ? The answer is supposed to be ''Blitzkrieg'' .Another  view which has escaped attention is that the Germans had a significant advantage in the intelligence field.Here is some information which I have uncovered from several sources:

EASI is European Axis Signal Intelligence in World War II   As Revealed by "TICOM" Investigations and by Other Prisoner of War Interrogations and  Captured Material, Principally German

Decrypted secrets: methods and maxims of cryptology , p474
The Chi-Stelle of the German Reichswehr, according to Huttenhain, broke the traffic between the French War Ministry and the French army departments early in the 1930s. However, their encryption was miserable: a numeral code which remained fixed for many years was superencrypted by a periodic VIGENERE modulo 10 with a period varying between 7 and 31. All signals could be read. Only between Paris and Savoy was a different method used, involving a transposition for superencryption. In 1938, OKW's Chi succeeded here, too. When war started on September 3, 1939, the French War Ministry ordered this method to be used throughout. Thus, the Germans could read the French wireless signals from the first day without delay, which explains the advantages they had in the battle of France in June 1940. France had made the mistake of adopting as her main method an encryption method that had already been in restricted use for some time.

EASI vol 4 ,p140 ,141
French systems 1933-1939 - Mettig stated that during the years 1937-1939 , continuous and significant successes were obtained by the Intercept Control Station against French Army systems. In the crises of 1937 and 1938, the Germans read the systems used by the French on the wireless net which radiated from Paris  to the static French formations within France.These systems, designated by the Germans as  F 90 and F 110  were described by Dr. Otto Buggisch, one of the leading Army cryptanalysts, as French Army systems based on a four-figure code. In one case, the encipherment was by means of a periodic additive ,in the other it was an ordinary transposition, the transposition key being obtained from a key word which itself was taken from the code. Solution, said Buggisch, was obtained by methods generally known in cryptanalytic circles.
From EASI vol 1:

Belgian systems  1933 -1939 - The complete order of Battle of the Belgian Army was known to the Germans in 1939 at  least partly through the reading of Belgian systems. Huettenhain, one of the leading cryptanalysts of the Signal Intelligence Agency of the  Supreme Command of the Armed Forces (oKW/Chi) , described the Belgian Army system as a 5-figure code used with substitution tables in such a way that the first figure of each group remained unchanged and the second and third were each enciphered Individually with types substitutions that could be varied with each message.

Dutch systems 1933-1939 - Mettig states that the Dutch Order of Battle was also available to the German Army at least partly from cryptanalytic achievements.The maneuvers of the Dutch army in 1937 were covered by the intercept stations of the Army. Very simple techniques, principally double transposition ciphers; were used and these were read by the cryptanalysts of the Intercept Control Station without much difficulty As a result, Dutch Order of Battle was established down to battalion level.

EASI vol4 ,p143,144,145
The failure of the cryptanalysts of the Intercept Control Station to solve independently, the French Army system succeeding the F 110 was another indication of their inadequacy. In early autumn 1939, the French replaced the peace-time systems, F 90 and F 110, with a new war-time system whose name is not known from TICOM sources. The Army cryptanalysts found themselves unable to cope with the situation and called the cryptanalysts of the Signal Intelligence Agency of the Armed Forces, (OKW/ Chi) to their aid. Huettenhain, one of the cryptanalysts of OKW/Chi, was sent to the Army Intercept Station at Frankfurt/Main to aid in the solution. Among his papers were two memoranda describing the work he did there.In the memoranda, Huettenhain reported that the task was accomplished, with the aid of his own colleagues of OKW/ Chi by October, (1939), so that all the September material could be read retrospectively. The system continued to be worked on successfully through October  and in November, Dr. Huettenhain returned to his own agency, the system solved. It may be noted that the head of the Army station requested Huettenhain to convey the thanks of the Army to the Signal Intelligence Agency of the Supreme Command of the Armed Forces (OKW/Chi) for the assistance given to the Army's cryptanalytic sectionThe system was decoded by the Intercept Control Station successfully until the German offensive of the spring of 1940. At this time the French began to use systems in the forward echelons which the cryptanalysts of the Horchleitstelle were unable to solve.Mettig remarked that the Army cryptanalysts both of the forward units and of the Intercept Control Station (Horchleitstelle) finally concentrated on two machine systems, the C-36 and the B-211.Neither was solved, however, until after the cessation of hostilities with France.
Summary of the 1939-1941 period - Although the cryptanalytic achievements of the Intercept Control Station (Horchleitstelle) during the years 1939-1941 were minor, their success in intercepting traffic and decoding solvable known systems was of great aid to the German Army. Mettig stated that all messages on the French system which succeeded the F110 were read from late 1939 until the spring of 1940 when the system changed; and that these messages, despite their administrative nature helped to fill in the tactical picture.For example, the strength of units being set up on the training ground at Mourmelon was estimated by statistics of water bottles and blankets. It was possible to deduce facts about the shortage of armor-piercing ammunition with the French infantry units. Similarly, the conversion of the Second and Third French Cavalry Divisions to Armored Divisions in the area northeast of Paris was ascertained in December 1939. By the end of 1939; the complete Order of Battle of the French Army was available to the German Army from the reading of French traffic. The capture of a copy of the British War Office Code in Norway in 1940 (and of another copy at Dunkirk in June of that year) afforded the British section its first successes and furnished a constant and important source of information from that time until 1943, when the British discontinued use of the code. In this period the Germans realized the inadequacy of their personnel and effort, and set about correcting them. and remarked that in his opinion such a large cryptanalytic task could not be done by the Army High Command either then or in the near future.

British intelligence in the Second World War vol 1 ,p163
During the planning and the carrying out of the attack on France the work of the enemy intelligence department of the General Staff of the German Army was of crucial importance and its value fully justified the prestige which the department had always enjoyed. The work has been described by General Ulrich Liss, head of the department from 1937 to 1943. He emphasizes that partly on the basis of British army documents captured in Norway, which provided all it needed to know about the British order of battle, and partly from the cypher traffic between the French War Ministry and the army groups, armies and home authorities, most of which it read from soon after the outbreak of war until 10 May, the department had a very comprehensive and accurate knowledge of the dispositions and qualities of the Allied forces. This influenced the selection of the precise point of the German break-through on 9 May; established that on the eve of the campaign German forces exceeded the French by two to one; helped the Germans to appreciate that the Allied armies would advance to the Dyle when the attack began; and reduced German anxiety by strengthening the assessment that the French would be unable to launch an effective counter-attack on the flank of the main German thrust. In addition to the successful exploitation of captured documents and Sigint, the department made good use of photographic reconnaissance in determining in advance of the offensive such things as road capacities, defences, physical obstacles and floodable areas. During the campaign its intelligence continued to be good, and Sigint continued to be the best source.
Delusions of intelligence: Enigma, Ultra and the end of secure ciphers , p44
During the mid-1930s, Germany had focused on her immediate neighbors, primarily France. The Marine's B-Dienst watched the French Navy closely during the interwar period, and this continuous attention paid off. By the outbreak of war, four important French tactical codes had been solved almost in their entirety. In one clear example of the rich dividends of continuity, the Germans benefitted from tracking the French Navy's exercises in the mid-1 930s. In June 1936, the B-Dienst had deciphered a scant twenty messages sent on a special system during French exercises. When France switched its codes upon declaration of war in 1939, the French Navy turned back to this 1936 system, to the B-Dienst staffs delight.
The codes mentioned in the notes p246 : Code de Service Tactic; Tous Batiments Militaire (rated most important by German officers), Batiments de Guerre (French Navy cipher) and Rayon Diplomatique.
From EASI vol 1 :

German Radio Intelligence , VII. Campaign in the West (1940) ,Section written by Colonel Randewig  .
Prior to the start of major operations the information obtained by radio intelligence from the northern sector held by British and French forces was not particularly valuable because of the great distance involved - for instance, 210 miles between Lille and Muenster — and because of its largely technical character. Thus, all intercept units were thoroughly familiar with the French system as a result of the many field messages which had been copied. The intercept units of Army Group B were also familiar with the Belgian, Dutch, and British systems. As early as December 1939 the Germans broke a special cryptographic system used by the French command in radio messages to the armies and military district headquarters. It had been used contrary to regulations prior to the opening of hostilities in September 1939. The Germans were able to solve this system because the radio station guilty of the violation was reprimanded and thereupon repeated the earns messages in the proper system. Their contents revealed a certain amount of organizational information, for example, the fact that the French 2d and 3d Cavalry Divisions had been reorganized into the 1st and 2d Armored Divisions and were due to move into their assembly area northeast of Paris by 1 January 1940. However, this type of incomplete information could generally be considered only as a supplement to and confirmation of other intelligence concerning the enemy. It was not possible to deduce the enemy's order of battle from radio intelligence alone.
Nevertheless, the Germans could identify the probable concentration areas of the French and British armies from the practice messages sent by the field radio stations, although the boundaries of army groups, armies, corps and divisions could not be established with any certainty. Greater clarity prevailed about the fortified area behind the Maginot Line in the south. Enemy forces stationed near the Franco-Swiss and Franco-Italian borders were not observed according to any regular plan. Spot-check intercepting failed to pick up the French Tenth Army in the place where it was presumed to be by the German command. However, radio intelligence did indicate the presence of the French Sixth Army.
Intercepted radio messages from the British Expeditionary Force enabled the Germans to conclude that the following units had been transferred to the Continent: one army headquarters under the command of General Lord Gort, three corps headquarters, five regular, partly motorized divisions (apparently the British 1st to 5th Divisions), one armored division, as well as several divisions of the second and third waves, the exact number and numerical designations of which could not be ascertained.
The intercepted Belgian and Dutch messages permitted only one conclusion, namely that their preparatory measures were directed against Germany exclusively. Belgian traffic was characterized by good radio discipline, whereas the Dutch were more careless.
The missions which OKH gave to the army group headquarters concerning radio intelligence were merely supplemented by the latter. Army Groups B and A were requested to give priority to intelligence pertaining to the British army as well as the French First and Seventh Armies. Special value was attached to ascertaining at an early date whether the French Seventh Army ("I'armee d'intervention en Belgique") would immediately march into Belgium.
An evaluation of the radio traffic during the first phase of the campaign in the West — with the exception of the Dutch traffic, which practically disappeared after five days of fighting — leads to the following conclusions: The different operating techniques made it easy to distinguish rapidly between French, British, and Belgian units. Generally speaking, the enemy transmitted too many messages and thus enabled the Germans to intercept them without any trouble. However, except for serious violations of radio security, such as the sending of messages in the clear, German intelligence was confronted with considerable difficulties, because the majority of the cryptographic systems proved unbreakable.
In view of the rapid conduct of operations, particularly those of motorized and armored units, the information obtained by German radio intelligence was of secondary importance in comparison with that covered by ground and air combat reconnaissance, especially the close reconnaissance.
So from the information presented it seems the Germans has access to several high level French codes both Army and Navy from prewar to May 1940.Belgian and Dutch systems were also read.During May the French changed their codes but the damage was done.
The role of intelligence in the fall of France should receive more attention from historians.

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