Protecting ULTRA – Must try harder?


ULTRA was the code-name given to radio interception and decryption of Axis radio communications. While many people know that this affected a lot of German radio communications, what is less well known is that some Italian communications were also routinely decyphered. For a lot of good detail, see Chris’ blog at this link.

Masking Knowledge

One of the problems faced by the Allies was to hide the fact that they had read a message, while still taking advantage of it. Otherwise there would be the risk that a reasonably smart enemy would quickly figure out what was going on, and change cypher methods. In the Mediterranean, what happened was that reconnaissance planes were sent out, often from Malta, to ‘discover’ convoys that had been reported in ULTRA. This way the Axis had a good explanation why the convoy was discovered, and would not get suspicious. The story below shows the wisdom of this approach.


Adrian Warburton and fellow air crew from No. 69 Squadron detachment on Malta. Amongst other tasks, planes from this reconnaissance unit were often task to cover up for ULTRA intercepts, being sent out to ‘discover’ a convoy where the route was known by radio intelligence. IWM.

German Unshakeable Conviction

Just before the time of CRUSADER, suspicions had been raised amongst German naval staff about the repeated failure of U-boat patrol lines in the Atlantic in engaging convoys. On 19 November, the war diary of Adm. Dönitz, Commander of the German submarine fleet, the translated version of which has been transcribed on U-Boat Archive, notes:

A likely explanation would be that the British, from some source or other, gain knowledge of our concentrated dispositions and deviate thereby encountering perhaps boats proceeding singly.  This knowledge could be gained by the enemy:

1) […]

2) By deciphering our radio messages.  This matter is being continually examined by the Naval War Staff and is considered as out of the question.

In other words, there was complete faith in the security of the German naval encryption system at this time. While this unbreakable security may have been the case for the Kriegsmarine (although I doubt it), what was not considered was the repetition of naval signals or sending of related signals through other networks, e.g. the Luftwaffe, or by Allies. This was of course not as much of an issue in the Atlantic, but it certainly was in the Mediterranean.

0023 watermark

Rommel during a photoshoot with Regia Marina Submarine officers, most likely Zoea during her first trip to Bardia in May 1941. Collection.

Concerns in North Africa

About 10 weeks before the above diary entry, Panzergruppe Afrika wrote to the German military attache in Rome, General von Rintelen, regarding shipping between Italy and North Africa[1]. The memo covers a range of issues relating to harbours, distribution of shipping space between the Axis partners, and also radio security, or rather the lack thereof on the Italian side. It states:

Shipping losses on the route to Tripolis are especially high. […] Furthermore the English (sic!) without doubt gain their information from radio traffic, which gives them a fairly clear picture about the departure and the individual situation of ships (see attachment). Regarding a reduction of radio traffic, compare minute of the meeting between General Bastico and General Rommel on 17 August 1941, sent by this Ia Nr. 25/41 Geh.Kdos. Chef – Sache on 18 August 1941.[2] 

Furthermore it does not seem impossible that the English are using espionage (Naples?).

The attachment referred to above is of great interest, since it shows a number of cases where the ULTRA guard seems to have been let down sufficiently to arouse severe suspicions on the Axis side. It is quoted in full below:

Attachment to Kdo. d. Pz.Gr.Afrika Abt. Ia/O.Qu.Nr. 26/41 g.Kdos. Chefsache of 1 September 1941.

1) The following submarines were discharged in Bardia up to 30 August:

a) 10 August Zoea
b) 12 August Coridoni
c) 16 August Atropo 

a) Arrival of Zoea was repeatedly moved. Announcement on German and Italian radio net. According to report DAK English air raids happened every evening on the announced arrival days. The locally ordered discharge at 5 AM on 10 August remained undisturbed until the departure.

b) Corridoni arrived as previously announced on the evening 12 August. From the start of discharging rolling enemy air raids occurred.

c) Arrival time of Atropo was foreseen for 15 August, but was moved. Nevertheless on the evening of 15 August a heavy English air raid took place. Atropo then arrived without announcement on 16 August and could be discharged without disturbance.


a) For 0900 hours 5 August the arrival in Bardia of the supply steamer Cicilia had been announced. As was found out later, this announcement was based on an error. Cicilia was meant for Benghazi. Again in this case on 5 August a particularly active English air activity reigned over Bardia.

b) According to Geh.Kdos. of Chief of German liaison staff at the Italian navy No.4 558 on 24 August at 0300 hours AM steamer Bellona was to arrive at Bardia. DAK reported for 24. August 0400 hours AM english air raid on harbour. The sea area outside the harbour was systematically illuminated.

3) It is of particular note that the English air raids always happened at the times of day notified in the announcement transmitted on the Italian radio net. (report DAK)

4) The Italian radio traffic is being supervised by German listening posts. According to Major SINGER, radio interception analysis office Southeast, even after three changes, every Italian key was decyphered.

It is clear from this that the suspicion was squarely on the Italians. What is also appears clear is that somewhere something had broken down in the protection of the radio interceptions (whether ULTRA or not), and the measures taken to intercept relatively unimportant Axis traffic into Bardia put at risk the capability of the Commonwealth to listen into Axis radio nets. Additional protection would probably have been easy, by just laying on more attacks at random times, to prevent a pattern from forming. But of course, air assets came at a premium in the Western Desert air force during the summer of 1941, with demands on the few available squadrons being very high.


[1] Command Panzergruppe Afrika, Abt. Ia/O.Qu. Nr.26/41 g.Kdos.Chefs., dated 1 September 1941. Copy held in NARA, Panzergruppe Afrika files.

[2] Afraid I don’t have a copy of this.

9 thoughts on “Protecting ULTRA – Must try harder?

  1. The were many cases where the Germans attributed Allied successes to poor Axis signals security. In N.Africa the Italians were an easy scapegoat as indeed many of their low/mid level codes were easily decoded.
    The ability of the Allies to take advantage of the Enigma cipher machine was never in danger, as the Germans did not have the resources to replace the huge number they were using ( depending on the author from 20,000-200,000 , the most accurate number seems to be 40,000) .


    • Hi Chris

      My guess is that this time they may have been right on the assumption. 🙂

      I didn’t think of replacing Enigma, but rather of adding additional security to the existing method, such as the fourth wheel to the naval enigma.

      All the best



      • Well they did increase its security during the war. I’ll write a piece about that in the future. Just to give a general idea : changing the sequence of the rotors every 8 hours, moving the slow moving rotor by hand in the middle of a message, changing the plugboard connections every 8 hours (this was stopped as it created problems!) and of course the mechanical modifications Uhr-
        and UKW-D –
        One that was designed but not introduced before the end of the war was the
        Lückenfüllerwalze -
        UKW-D and the Lf would have shut down Bletchley Park had they been used in numbers…


      • That’s what I mean. I also find it astonishing that nothing was done about Italian radio security when it was clearly as deficient as the report makes out.


  2. Well you might be overstating the ability of the Germans to make their Allies conform to security regulations. The Italians were a sovereign country and no one could order them to do something. Even in the Eastern front the Germans were always complaining about the security of their allies traffic.
    The Germans did inform the Italians about their poor security but no serious changes were made. In the Italians defence it was low/mid level codes that were vulnerable. Their high level codebooks more or less defeated Bletchley Park.


    • I was thinking more along the lines of the Italians making changes out of self-interest once they were told how vulnerable their code books were, rather than the Germans ordering them to (which I agree would never have happened in the time frame). While I don’t understand much about the terminology, I would have thought that the C-38 and Italian Enigma, both of which were read, would have been considered high-level codes?


  3. Well the Enigma seems to have been used rarely. The C-38 was mostly used for the N.Africa shipping traffic, which was very important so you can consider it ‘high’ level although i don’t think the Italians would agree.


  4. Pingback: Bardia, Halfaya, and the January Offensive – The Crusader Project

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