Read The Secrets of Station X Online
Authors: Michael Smith
Despite the presence of the SLU at the headquarters of the British Eighth Army, the
Crusader
offensive proved beyond doubt that the best use of
Ultra
was in providing the details of enemy strength and dispositions, and often future plans, rather than in tactical information during the heat of the battle. The sheer length of time it took for reports to get from Bletchley to Libya meant that Hut 3 could not compete with the mobile Y Special Wireless Section of Royal Signals and Intelligence Corps personnel in armoured cars who were at the front.
‘Despite the amazing speed with which we received
Ultra
, it was of course usually out of date,’ recalled Bill Williams, who served as an intelligence officer in North Africa.
This did not mean that we were not glad of its arrival for at best it showed that we were wrong, usually it enabled us to tidy up loose ends, and at worst we tumbled into bed with a smug confirmation. In a planning period between battles its value was more obvious and one had too the opportunity to study it in relation to context so much better than during a fast-moving battle such as desert warfare produced.
Auchinleck’s defeat of Rommel forced the
Afrika Korps
back to el Agheila. But within a few months, the Germans had regained much of the ground they had lost and were back in Benghazi. This was at least in part the result of a serious misreading of a decrypt from the Italian C38m cypher which was wrongly seen as suggesting that the
Afrika Korps
did not expect to reach Benghazi. But it was also a result of the failings of the British tactics. Bennett said,
The troops on the ground on our side were still not used to receiving high-level information. They were also using the wrong tactics. The gunfire was never sufficiently massed to do enough damage to the enemy until Auchinleck managed to change it under pressure in the late summer of 1942.
Although the
Red Luftwaffe
Enigma gave good warning of a German offensive scheduled for the end of May of 1942 and aimed ultimately at regaining Tobruk, Hut 3 was unable to provide any information about Rommel’s precise plans, either before or during the Battle of Gazala. By mid-June, Auchinleck had decided to withdraw across the Egyptian border to a stronger position at Alam Halfa, leaving the 2nd South African Division to hold Tobruk as a fortress inside the enemy camp.
Within a week, it had surrendered. Churchill, who was in Washington conferring with Roosevelt, was bitterly
disappointed
. ‘I did not attempt to hide from the President the shock I received,’ he would later recall. ‘It was a bitter moment. Defeat is one thing; disgrace is another.’
But the tide was about to turn, and as a direct result of a dramatic improvement in the work of the codebreakers at Bletchley Park which included much greater coordination between the codebreaking process and traffic analysis.
During 1940, three teams of officers and mostly female
civilians
began working on trying to analyse the radio networks and in particular break the German system of daily changing
callsigns
.
They were based at MI8 offices in Caxton St in London, at Harpenden and in Hut 3. This process, subsequently known as ‘log-reading’ and then later ‘traffic analysis’, had produced a wealth of usable intelligence during the First World War and had already proved its worth in Hut 4, the Naval Section, where Harry Hinsley was obtaining so much important intelligence. It was not initially regarded by many of the new young
codebreakers
and intelligence officers working on German Army or
Luftwaffe
traffic in Hut 6 and Hut 3 as likely to produce much intelligence. The reverse soon proved to be the case. Using a variety of information noted down by the ‘Y Service’
operators
on their message logs, including callsigns, locations from direction-finding or identifications from RFP or Tina, and the simple German operator plain language chatter, which when units came under pressure during the battle often contained violations of basic communications security, they were able to build up complete pictures of the units involved and provide fresh intelligence and cribs which would help in the
breaking
of Enigma. A new unit, VI Intelligence School, with an establishment of 233 staff, a mix of male members of the Army Intelligence Corps and female ATS soldiers, was set up in March 1941 and based initially at Beaumanor. Even at this stage it was suggested by some in Hut 6, now converted entirely to the idea that ‘traffic analysis’ was a producer of vital intelligence, that it should be based at Bletchley. It moved there in May of 1942 and was attached to Hut 6, initially as the ‘Central Party’ but later as Sixta, a title derived from Six Traffic Analysis.
‘Our job was to analyse the operator chat,’ recalled Jimmy Thirsk, a 27-year-old librarian recruited into the Intelligence Corps to work as a log-reader.
If you had a section of the
Luftwaffe
, say they were in France with their headquarters in Dijon, and perhaps they had ten outstations round in that area. Every morning they would start up. Each station had a three-letter callsign and they would
change that at midnight according to a pre-set pattern and then they would call up the outstations just to make contact. Just to make sure they were all awake and working and they would chat to each other in clear German. This operator chat was going on all day long and the intercept operators logged it all down.
Most of the messages were teleprinted from the intercept stations but the logs used to be brought mainly by motor cycle dispatch rider. You would be allocated a number of nets. If they were small ones you might have two or three but you might have just one. Each day you would plot the radio net. We had coloured pencils, and you made a circle with a dot in the middle as the HQ and then the outlying stations were round the
circumference
of the circle with a line drawn from each of the
outstations
to the centre and you would note the number of messages passing on each link. Then at the end of the week you had the dreaded weekly report and you had to go through your stuff for the week and compile a report. It was pretty dreary stuff at times.
Their work was assisted by the capture of the
Luftwaffe
callsign book, the
Rufzeichentafel Ausgabe B
, from a German Army unit in the North African desert in December 1941. The
Luftwaffe
was clearly unaware of its capture and continued using the same system for the next two-and-a-half years.
Longer-term traffic analysis was carried out in the Hut 3 Fusion Room which used all the information produced by
various
parts of Bletchley Park to build up a complete picture of the enemy radio networks. Joyce Robinson had a degree in German and after a brief spell in the Civil Service joined the ATS and was posted to Bletchley where she was allocated to ‘fusion’.
It was really a sort of consolidation of information from a lot of quarters after material had been dealt with operationally. It was departmentalised according to networks, or keys, where a group of one, two or more people considered the behaviour of certain things so that you knew your network. You were
sometimes able to help Hut 6 when they had difficulties with decoding, with a change in the wheels.
One of her ATS colleagues was Jean Faraday Davies, who was pulled off a German course at the University of London and sent to Bletchley. The Fusion Room coordinated information produced by the log-readers with the intelligence from the decyphered messages, Faraday Davies said. ‘Our function was to take these two sources and feed it out in two directions to enable interception to go on or to help decoding.’
The move of the traffic analysts to work alongside Hut 6 had increased the availability of cribs, together with an increased understanding of how the Army Enigmas worked. Up until now the delay in breaking
Chaffinch
, the main
Afrika Korps
Enigma, had been up to a week. From the end of May, they were able to break it daily, albeit with some delay. Another
Panzer
Army Enigma, designated
Phoenix
and broken briefly at the end of 1941 following the capture of three machines and a number of keys, was read continuously from 1 June. A third Army Enigma,
Thrush
, giving details of air supplies, was also broken.
Hut 6 was now able to read all the
Luftwaffe
keys,
including
the
Red
which had been continuously broken since May 1940; two relatively minor keys called
Locust
and
Gadfly
; and two much more important keys which, in a security blunder by the Germans, were closely linked.
Primrose
, the cypher of the
Luftgau Afrika
, the air formation responsible for administration and supply of the
Luftwaffe
forces in North Africa, was not only an important source in its own right, its keys were also used later by
Scorpion
, the cypher used for communications between the
Flivos
and the ground forces.
During the North Africa campaign,
Primrose
became as high a priority for Hut 6 as the
Red
cypher. ‘It was very important,’ said Susan Wenham, one of the Hut 6 codebreakers.
Every day the key was changed and about 3 o’clock in the
morning
Primrose
used to send a tuning message through, a very short little message. It was always on the same wavelength and it was always recognisable. So people on the nightshift would watch out for this message and, when they got it, they would tinker about with it and we could quite often break on that message.
Red
had an enormous quantity but it didn’t have a nice convenient tuning message that you could find.
Hut 6 was given much more time to get into the Army keys as a result of an extraordinary error by the
Luftwaffe
, Stuart Milner-Barry recalled, describing 1942 as Hut 6’s ‘
annus
mirabilis
’. Paradoxically, it was due to an increase in the number of different
Luftwaffe
Enigma keys introduced with a view to making the systems more difficult to crack. It actually achieved the exact opposite, Milner-Barry said.
The Germans suddenly realised that there was no objection, and obviously great advantage in security, in using a large number of different keys for the different major units of the
Luftwaffe
. However, with characteristic blindness the enemy undid much of the good that this step might have done him, for instead of making up entirely separate keys he rehashed old ones on a delightfully simple plan. The effect of this was that, every other month, the majority of Air Force keys were in our hands for the decoding and a tremendous boom ensued which taxed our resources to the utmost.
Since
Scorpion
’s keys were now predictable, Hut 6 decided that it could be decyphered in Heliopolis, making it available to the commanders far quicker than any other material. Because the
Flivos
needed to keep in close contact with the battle in order to coordinate air attacks with the movement on the ground,
Scorpion
provided more details of the fighting, the troop
positions
and air activity than any of the other cyphers had before.
‘It contained much “hot” operational news; it was easy to
break, for the daily settings could be predicted in advance,’ said Bennett. ‘It was decided to radio them in advance from Hut 6 to Cairo and to send an experienced officer out to compose signals on the spot.’
Meanwhile, during July and August, the number of mobile Y units in North Africa was doubled and they became much better integrated into the command structure. Traffic analysis and direction-finding were improved and the Intelligence Corps and RAF codebreakers attached to the Special Wireless Sections expanded their exploitation of enemy tactical codes and cyphers.
Ultra
was now totally in the ascendant. In the first nine months of the Special Signals Link to the Middle East, between March and November 1941, Hut 3 had sent just over 2,000 signals to Cairo. Between November 1941 and July 1942, it had sent five times that figure.
Desperate for a victory and fully aware of the information from
Ultra
that was now available, Churchill decided it was time for change. Auchinleck was a fine general but did not have the necessary killer instinct. He brought in General Harold Alexander as Commander-in-Chief Middle East and appointed General Bernard Montgomery to take command of the Eighth Army.
Within days of his arrival, Montgomery was the beneficiary of a major piece of
Ultra
intelligence that was to change the military’s view of the codebreakers. On 15 August, Rommel, newly promoted to Field Marshal, explained to Hitler what he planned to do next. The details of the plans had to go first through his direct commander, Field Marshal Albrecht Kesselring, the German Commander-in-Chief South, and they were transmitted using the
Red
cypher, which Hut 6 had no problems reading.
Two days earlier, Montgomery had outlined what he believed the Desert Fox would do. It matched the signal sent to Kesselring almost to the letter. Rommel intended to attack around the time of the full moon due towards the end of August, swinging south around the end of the British lines before striking north to come
up behind the Eighth Army, cutting it off from Cairo. But to do so he would have to cross a major obstacle: the Alam Halfa ridge.
‘Monty arrives in the middle of August and is told not to go and take charge until the next morning,’ said Ralph Bennett.
He goes up to Alam Halfa to have a look round, one day before he is going to take over. He sums up the situation and realises that if Rommel is going to attack he will almost certainly do so on a route that will take him through the Alam Halfa ridge.
A few days later, Rommel tells Hitler what he is going to do, which is exactly that. We get this signal and we tell Monty. So there is Monty, the new boy, who has just made a pep talk to his troops, now knowing that his hunch as to what Rommel will do is exactly right. He can’t tell anybody about it but when Rommel attacks Monty is ready.