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 Italian communications were also routinely decyphered. For a lot of good detail, see Chris’ blog at this link. 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.

Just before the time of CRUSADER, suspicions had been raised about the repeated failure of U-boat patrol lines in the Atlantic to succeed in engaging convoys. On 19 November, the war diary of Adm. Doenitz, 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.

About 10 weeks before that 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.

Luftwaffe Appreciation of RAF Strength in North Africa, 20 November 1941

The item below is from the UK National Archives. It is an ULTRA/Enigma intercept, and I am comparing it with the actual RAF strength (another National Archive file kindly provided by Michele Palermo) for the same week. There are some assumptions in there which I’d happily correct, if someone knows better.

  1. Operational Units
    1. Single-engine fighters: 19 fighter squadrons with 450 – 500 Tomahawks and Hurricanes, of which at the moment 390 are in the front area, according to air photography. [actual: 17.5 squadrons and one flight of Fleet Air Arm Martlets, with another 4 more forming, 280 operational with another 394 operational in 14 days – so this is a serious over-estimate by German intelligence]
    2. Heavy fighters: 3 squadrons with 60 Beaufighters, at least 1 squadron of these in the front area. [actual: 1 squadron with 16 aircraft, with another 3 forming, and 8 more aircraft becoming operational in 14 days – another serious overestimate]
    3. Day bombers: 12 squadrons with 200-250 Maylands and Blenheims, of which at the moment about 170 are in the front area according to photography. 1 squadron, equipped with Boeing Fortress I aircraft, probably being formed in the Delta area. The greater fighting value of the Maryland as opposed to the Blenheim permits its employment as an auxiliary heavy fighter: low-level attacks and, above all, attacks on transport aircraft have frequently been successfully carried out (armament: 4 fixed MG’s firing forwards, 2 firing backwards, and in addition one moveable twin MG firing upwards and one firing backwards: this has been established from captured aircraft.) [actual: 9 squadrons of light bombers with 2 squadrons and 1 flight of Maryland/Blenheim reconnaissance, with a total of 144 bombers and 36 reconnaissance operational; none forming, and another 193 light bombers becoming operational in 14 days. 3 Fortresses only, which were on special assignment. Also half a squadron of Boston III active with 8 planes, with the half forming, and 15 Boston III to become active in 14 days – this is a reasonably accurate estimate; regarding the use of the Maryland as a heavy fighter, it rather appears to me that (with one exception I am aware of), Blenheims served in this role]
    4. Night bombers: 5 squadrons with 125 Wellingtons, night attacks on Cyrenaica are carried out every night, aircraft starting from Suez Canal area, with advanced landing grounds in the Western Desert (gliding attacks and flare-dropping carried out). [actual 5 squadrons with 100 planes operational and another 22 to become operational in 14 days no squadrons forming – this is an almost perfect estimate flare dropping however was carried out by Fleet Air Arm Albacores, which are not included in this strength report]
    5. Transport aircraft: 2 transport squadrons with 25 Bombays and/or Valentias and 20 Lockheeds. 6 Bombays were employed on night 16-17/11 to drop parachute sabotage detachment in Cyrenaica (this is confirmed by the shooting down of one aircraft and the papers recovered from it). [actual 2 squadrons with 24 Bombays/Valentias operational and another 4 to become operational in 14 days, no squadrons forming; 1 squadron with no Lockheed/Douglas active, and another one forming, with 16 planes to become operational in 14 days – again a very reasonable estimate)
    6. The shortage of personnel existing after the units have been brought up to strength as regards material seem to have been overcome. It must be assumed that there exist strong reserves in aircraft parks for fighter and bomber units, since there has been a constant flow of supplies by air to Africa (U.S.A. material) and via Mediterranean (English material) (cf. air photograph of aerodrome 25 km west of Hedouan. [this is a correct interpretation of the situation]
  2. Scale of Effort

    Night bomber units since 1/9/41, regularly at about 15 per cent daily. It is probable that with the increased scale of effort since early November the maximum possibilities of these units have been reached. On the other hand fighter and day bomber units have been carefully withheld up to the beginning of the month. Their present increased scale of effort is normal, having regard to the situation (scale of effort since … at the moment reaches at the most 25 per cent of the actual strength). It thus appears that scale of effort in present form is possible for some time ahead, and may even rise for a while.

Actual scale of effort:

  • Assuming 2 sorties per day for single-engine fighters, the capacity usage was 10% in this week, although that is a big if, since 521 of the 673 (plus 18 Hurricane recce and 16 Hurribomber sorties) sorties of all fighters are unspecified and could include Beaufighters and Blenheims. For the Beaufighters (assumed 1 sortie), usage was 26% of capacity, 29 sorties.
  • Assuming 2 sorties per day for Blenheims and Marylands, the effort was about 9%, 185 sorties (plus 5 Blenheim fighter sorties) with 144 operational planes, but there are also 64 unspecified bomber sorties, some of which will be Fortresses, some others Wellingtons and light bombers.
  • For the reconnaissance Blenheims and Marylands, usage was only 7%, assuming one sortie per day as capacity. A total of 18 sorties was made. But there are another 23 unspecified sorties.
  • Assuming (based on nothing but my own thoughts, if someone knows Luftwaffe capacity assumptions, please let me know) total capacity is 1 sortie per day for the Wellingtons, the effort in this week was about 21%, at 148 sorties compared to 100 operational planes.
  • For the transport fleet, utilization was also low, at 9% (assuming 1 sortie per day), 15 sorties of Bombays are recorded]

The numbers appear to show a very strong focus on the initial gaining of air superiority. For example, in the following week, the Blenheims and Marylands had 265 sorties with unchanged operational numbers, a rate of 13%. Wellington sorties remained practically unchanged, while fighter sorties increased to 777 on unchanged numbers, or a rate of 20%. Unspecified bomber sorties tripled however, so the actual utilization was higher.

Compared to the Luftwaffe expectation, the Desert Air Force was operating at a low capacity rate, if the assumptions are correct. This is partially explained by the longer distance planes had to fly to get to their area of operations, I guess. But there are also questions raised e.g. by Australian Wing Cdr. Geddes in a special report, about the efficiency of the ground crews.

A day in the life of the Luftwaffe – Operations report by Fliegerfuehrer Afrika 23 Nov. 41

A day in the life of the Luftwaffe – Operations report by Fliegerfuehrer Afrika 23 Nov. 41

This operations report was sent on 23 Nov. 41 at 1730 hrs from Fliegerfuehrer Afrika Ic (intelligence officer) to Fliegerkorps X in Greece, and ITALUFT, the German Luftwaffe staff in Italy. The report was intercepted by the British decoding teams and decrypted at Bletchley Park. It can now be found in the National Archives in Kew, London. I have left the report in the original text, annotated it, and provided a glossary below. I also re-ordered it according to time.


Junkers 87 dive bombers of an unknown unit taking off in North Africa. Courtesy Bundesarchiv Bildarchiv.

Fliegerfuehrer Afrika Operations Report 23 November 1941

0401 hours

1 Ju.88 of the AFRIKA Kette carried out recce of the tracks BIR EL GUBI – GIARABUB as far as SIDI OMAR. No enemy M/T observed. N.E. of BIR EL GUBI a concentration of about 100 M/T.

0540 hours

2 Bf. 110 of Stab Stuka 3 on recce S. of DERNA as far as 30 degrees N. 1 Bf. 110 brought confirmation of the 2 field aerodromes. 1 Bf. 110 missing. (1)

0550 hours

15 Ju.87 of II/StG2 carried out attack on tanks and M/T concentration E. of BIR EL GUBI, with 5.5 tons of H.E. bombs accurately placed in the target area. Very strong fighter defence: 3 Ju.87 missing, 1 Ju.87 made forced landing. 1 Ju.87 crashed on aerodrome, crew escaped by parachute.(4)

0555 hours

18 Ju.87 of I/StG1 attack on field fortifications and a battery position E. of BIR EL GUBI with 6.05 tons of H.E. bombs: bombs on target: effect not observed on account of strong fighter defence: 2 Ju.87 missing. 1 Ju.87 made forced landing, crew wounded but rescued. (2) (3)

0601 hours

1 Bf.110 of AFRIKA Kette in BIR HACHEIM to BIR EL GUBI and BAB ES [??} E. of BIR EL GUBI concentration of ?40 M/T. Otherwise nothing observed. At 0622 hrs [?] Bf.110 of III/ZG26 broke off attack on concentration near BIR EL GUBI as fighter protection was not assured.

0735 hours and again at 0802 hours

1 Ju.88 of the AFRIKA Kette on photographic recce of roads, railways and aerodromes SIDI BARRANI to EL DABA: heavy railway traffic at railhead: aerodromes only partly covered on account of heavy cloud.

0945 hours

11 Bf.110 of III/ZG26 broke off low-level attacks S. and E. of BIR HACHEIM on account of contact with 30-40 Curtiss fighters. (5)

1140 hours

In square 6231 3 destroyers and 1 small merchant ship, course west.

[No time]

I/ and II/JG27 shot down 10 enemy a/c on freelance patrols and while escorting Stukas. 1 Bf.109 missing, 2 Bf.109 made forced landing.



  1. There was only one field aerodrome in the area, Landing Ground 125, occupied by Hurricanes of No.33 Squadron and Blenheims of No. 113 Squadron
  2. This was likely on 1 South African Brigade which was in the area, ‘masking’ Bir el Gubi and the Ariete division position there. From memory I believe that these attacks were not very effective, even though they were unpleasant.
  3. A loss rate of 20% per sortie must have been extremely worrying.
  4. 33% loss rate.
  5. This, together with the two preceding notes, shows that while the Desert Air Force may not have had the number of kills of its adversary, it did achieve its operational objective on this day, which was to inflict losses on the enemy strike force and keep them away from their target, or at least reduce their efficiency.

Afrika Kette – a small unit (Kette – Chain) equipped with long-range reconnaissance Junkers 88 and Messerschmidt 110, stationed in Greece but under control of the Fliegerfuehrer Afrika. Bf. 109 – Messerschmidt 109, single-engined fighter
Bf.110 – Messerschmidt 110 twin-engine multi-role plane (heavy fighter, recce, ground attack)
Curtiss – Curtiss Tomahawk single-engined fighter
Fliegerfuehrer Afrika – commander flying units Africa. Fliegerkorps X – Air Corps X in Greece, with head-quarters in Athens Tatoi airport. H.E. – High Explosive
Ju.87 – Junkers 87 single-engine dive bomber
Ju.88 – Junkers 88 twin-engined multi-role aircraft used as reconnaissance, medium bomber (level and dive), night fighter.
M/T – motor transport
Recce – reconnaissance
Stab – Staff squadron. For dive bomber wing 3 this was well equipped with recce and transport planes. StGSturzkampfgeschwader – dive bomber wing Stuka – Sturzkampfbomber – Dive bomber. ZGZerstoerergeschwader (destroyer wing), equipped with Messerschmidt 110 planes.