Wednesday, August 2, 2017

Compromise of Greek military and diplomatic communications in WWII

At the start of WWII the Kingdom of Greece, ruled by Ioannis Metaxas  (head of the 4th of August Regime) followed a neutral foreign policy and tried to avoid taking part in the conflict. However constant Italian harassment and provocations (such as the sinking of the cruiser Elli) and the transfer of Italian army units to Albania made it clear that war could not be avoided for long.

In October 1940 Italian forces invaded Greece, in the area of Epirus, and the Greek-Italian war started. The Greek forces were able to contain the assault and the Greek counterattack forced the Italians back into Albanian territory. After the defeat of a major Italian offensive in spring 1941 the front stabilized inside Albania.

At the time Britain was overextended with obligations in Europe, Middle East and Asia. However the British armed forces made a small contribution with an RAF expeditionary corps. When more British forces started to arrive in March 1941, their involvement gave Germany an excuse to become involved in the conflict.

German forces invaded Greece in April 1941 and made rapid progress due to the fact that almost the entire Greek Army was fighting in the Epirus area. The remaining units and the small British forces transferred to Greece in March-April 1941 were unable to stop them. Then in May 1941 the Germans were also able to defeat the Greek and British forces that had retreated to the strategic island of Crete.

Compromise of Greek military codes

At this time there is very limited information available on the cryptosystems used by the Greek Armed Forces in WWII. A Greek file dated 1938 (1) mentions the following Army cryptosystems: small unit code 1937, large unit code 1937, small unit code 1938, mobilization code 1937, cryptographic lexicon 1935. 

According to TICOM report I-58 in early 1941 the codebreakers of the German Army’s signal intelligence agency investigated a Greek 5-figure code enciphered with a 35 figure repeating additive sequence (2). Progress was made in the solution of the cipher but the campaign ended just as the system was starting to be exploited operationally.

c. Greek - In early 1941, B. solved a 5-letter code with a 7-cyclic recipherment (period of 35). Just getting to operational speed when the campaign ended.

Information on Greek Airforce ciphers is available from TICOM report I-170 (3), written by Dr. Otto Karl Winkler, a member of NAASt 4, which was the cryptanalytic centre of KONA 4 (Kommandeur der Nachrichtenaufklärung - Signals Intelligence Regiment). KONA 4 was a German Army signal intelligence unit assigned to cover radio traffic from the Balkans and the Middle East.

In the report dr Winkler said that in spring 1941 Greek AF single transposition messages were solved and translated.

My first employment was on the breaking and translating of Greek Air Force messages in Spring 1941. The unit was in BUCHAREST at that time and later it was at BANJA KOSTENIC in Bulgaria. C.O. was Hptm. SCHMIDT, head of the cryptography and translation department from then until Autumn 1944 was Prof. Alfred KNESCHKE, a Professor of Mathematics from Saxony.

The Greek Air Force messages were a matter of simple boxes, the text being sent in T/L groups. The indicator took the form of 3 letters which were always in a given position, the first three T/L groups and had to be knocked out before entering the cipher text in the clear box. This was broken by writing out the cipher text in vertical strips of varying depth and sliding them against each other until a few Greek syllables appeared above one another. After the initial break it became clear that a large part of the messages began with the words ‘parakalw', 'anaferw’ and ‘apesteilamen’ and that the width of the box was as a rule between 15 and 22 columns. On the basis of the above, initial words, all messages were tried out on the normal number of columns and nearly everything was read. I had less to do with the actual evaluation, firstly because the two departments were kept separate and secondly because we were kept fully occupied with our own job. In any case the content of the messages was usually of insignificant strategic value, although the continuous check on officer personalities, deliveries of stores and knowledge of airfields combined with D/F bearings indirectly contributed to considerable tactical results.

According to dr Winkler Greek Army and Navy codes were not broken until after the conquest of Greece, when captured codes were read during the Battle of Crete. It would seem that Greek military codebooks were captured in mainland Greece and then used to solve Greek radio traffic during the Battle of Crete.

Regarding Greek Navy ciphers there are translations of Greek naval radio messages in the Italian state archives (4). Thus it seems that some Greek Navy communications were read by the Italian codebreakers.

The Greek Government in Exile

After the occupation of Greece by the Axis powers the King and the politicians that had managed to leave the country constituted the Greek government-in-exile, based in Cairo, Egypt. During the period 1941-44 the Greek government and the military forces that it controlled supported the Allied cause. Greek forces fought in North Africa and in Italy, while the Greek Navy operated in the Mediterranean in support of British operations.

In the diplomatic field the goal of the Greek government was to promote Greek interests in the Allied capitals and in the period 1943-44 to try and find an acceptable solution to the problem posed by the rise of the Communist controlled EAM-ELAS resistance movement in occupied Greece.

Greek diplomatic codebooks

The Greek foreign ministry used a series of codebooks in order to protect its sensitive communications from eavesdroppers. These were the cryptographic lexicons 1927, 1931, Η (ITA), Φ (PHI) and Ι (IOTA).

Usually these codebooks were used without additional encipherment, however when messages of particular importance had to be transmitted then they were enciphered with bigram substitution tables.

One interesting characteristic of Greek diplomatic codes is that they allowed for inflection. Greek is a highly inflected language and in order for the plaintext to be encoded correctly it was necessary to take this peculiarity of the Greek language into account. The way the system worked was that an extra letter (or number) was added to each codegroup in order to designate the grammatical form of the word in question.

Examples of Greek diplomatic codebooks (5):

Lexicon 1927

Lexicon 1931

Lexicon Η (ITA)

Lexicon Φ (PHI)

Lexicon Ι (IOTA)

During WWII Greek diplomatic communications were read both by the Allies and the Axis powers.

US effort

According to the NSA report SRH-361 ‘History of the Signal Security Agency Volume Two The General Cryptanalytic Problems’ (6), Greek systems were worked on by a subsection of unit B-III-D of the Army Security Agency.

This unit initially worked on the communications of Far Eastern countries, specifically Nationalist China and the Japanese controlled governments of occupied China, Thailand and the Philippines. In April 1944 the functions of the unit were extended to cover the traffic of Bulgaria, Croatia, Czechoslovakia, Greece, Poland, Slovakia and Yugoslavia.
Greek traffic was examined because the unit had a classical scholar who also knew modern Greek. According to the report this was dr Aubrey Diller, who was assisted by Mary Fennel, Lieutenant Praxythea M. Coroneos and Elaine Pulakos.

In December 1944 the unit had about 50 workers, with 4 working on Greek ciphers. The Greek codebook GRB (lexicon IOTA) had been copied by the FBI in an undercover operation so messages on this system could be solved and translated without delay.

Other systems examined by the unit were the highly enciphered code GRA and a new codebook GRE that was used during the San Francisco conference. The latter code was enciphered with digraphic substitution tables but some traffic was solved and several hundred codegroups recovered.

A table dated September 1944, listing intercepts and decodes by country, shows that 1.333 Greek telegrams were received. Out of these 507 were original messages (the rest duplicates), of which 427 were deciphered and 417 translated or summarized.

German effort

Foreign diplomatic codes and ciphers were worked on by three different German agencies, the German High Command’s deciphering department – OKW/Chi, the Foreign Ministry’s deciphering department Pers Z and the Air Ministry’s Research Department - Reichsluftfahrtministerium Forschungsamt.

OKW/Chi effort

At the High Command’s deciphering department - OKW/Chi, Greek diplomatic systems were worked on by a subsection of main Department V. Depending on the source the unit was headed either by principal specialist Rudolf Seifert or by dr Poestgens (7).

According to Wilhelm Fenner (head of the cryptanalysis department of OKW/Chi), three Greek codebooks were worked on (8).

Pers Z effort

At the Foreign Ministry’s deciphering department Pers Z Greek systems were worked on by the group ‘Italy, Greece, Vatican, USSR’, headed by senior specialist (Oberregierungsrat) dr Adolf Paschke.

According to TICOM report I-22, paragraph 169 (9) three Greek codebooks were read by the unit:

Greek: there were three systems, all of which were read:

1) a clear 5 letter book, the fifth letter of which was dummy; this carried most of the traffic.

2) a clear 4 letter book, used mainly for traffic with Berne.

3) a four figure book used with bigram substitution of 30 tables of 100 bigrams each. It was used between London and Moscow, Washington, Cairo and Ankara. Traffic from London amounted to about 1 a day. The bigram tables changed according to the date.

Forschungsamt effort

At the Air Ministry’s Research Department Greek systems were worked on by Abteilung 9, Branch A, Section 2 (Czechoslovakia, Yugoslavia, Bulgaria, Greece, Albania) (10).

According to dr Martin Paetzel (deputy director of Main Department IV - Decipherment) ‘just two plain codes were read’ (11).

Examples of decoded Greek diplomatic messages

Decodes of Greek telegrams can be found in the TICOM collection of the German Foreign Ministry’s Political archive (12):


Translated telegrams


In WWII Greek radio communications were read by the Axis powers to a considerable extent.

During the Battle of Greece it seems that the solution of Greek military codes did not play a big role in the actual combat operations. However according to German sources Greek communications were read during the Battle of Crete. If this is true then the intelligence gained from reading Greek messages may have given the Germans a significant advantage during that costly operation.

Greek diplomatic codes were insecure and were read not only by the Axis powers but also by the US and British codebreakers. Although Greece was a small country its politicians and diplomats had regular meetings with Allied officials and they were kept informed of important diplomatic and military initiatives. It is reasonable to assume that some of that information was transmitted in insecure Greek codes.

From the German point of view it was a worthy investment to focus on the codes of small Allied countries since they did not have the expertise or the resources needed to secure their wireless communications.

Wilhelm Flicke who was in charge of OKW/Chi’s Lauf intercept station wrote in his book ‘War Secrets in the Ether’ (13):

Hitler's attacks on the small states of Europe from 1938 to 1941 had forced the governments of these countries to take refuge abroad in order to continue efforts for the recovery of national independence. Most of these governments in exile had gone to London. Here they maintained little ministries and kept in touch with their representatives in foreign countries, i.e. with their embassies, consulates, missions, delegations, and the like. They made extensive use of radio telegraphy and thus supplied raw material for the German intercept service. And this "raw material" was - first class!
Everything that the "big fry’’ (i.o. the governments or Great Britain, U.S.A, Soviet Union. etc.) strove to keep secret, these "little fry" diligently tattled. It was fun to read their messages. Poland and some of the Balkan governments were the worst.


(1). German Foreign Ministry’s Political archive - TICOM collection - file Nr. 3.676 - Griechenland 1940 - Korresp. betr. Neue milit. Schlüssel u. Vernichtung alter    

(2). TICOM report I-58 ‘Interrogation of Dr. Otto Buggisch of OKW/Chi’

(4). Archivio dell' Ufficio Storico della Marina Militare, Rome

(5). US National archives - collection RG457 - Entry 9032 - NR 664, 665, 666 'Greek Cryptographic Lexicon I, O and I, NR 703, 704, 705, 706 'Greek Cryptographic Lexicon Φ, H, 1927, 1931, NR 2104 'Greek Cryptographic Lexicon'

(10). TICOM report DF-241 ‘Part 1’, p10

(12). German Foreign Ministry’s Political archive - TICOM collection - files Nr. 2.256    Griechenland ‘’GC B 4251-450’’ Diplom. Verkehr Vollst. Entschlüsselt and Nr. 781 Griechenland 1944 Entschl. Verkehr zw. zahlr. Griech. Konsulaten.

(13). War Secrets In the Ether Part III by Wilhelm F. Flicke, p395-396

Acknowledgments: I have to thank Enrico Cernuschi for sharing the messages from the Archivio dell' Ufficio Storico della Marina Militare.

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