Shaftesbury and Wick, plus seventy-five sets in the Middle East and the Mediterranean. By June 1944, 515 sets were tasked on
Luftwaffe
and
Heer
Enigma, but even as late as January 1945, Hut 6 was ‘as short of sets as ever’: minor
Heer
and
Luftwaffe
ciphers were not being intercepted, and no attempt could therefore be made to break them.
The service authorities came to accept Hut 6’s view that Enigma interception was an indivisible problem, and allocated Army sets to
Luftwaffe
traffic, and RAF sets to
Heer
signals. Later, they also relinquished control of tasking the Army and RAF sets. In May 1943 Hut 6’s intercept control section under John Coleman specified the Enigma tasks to be taken by the intercept stations, and the number of sets to be allocated, but the stations remained under the administrative control of their parent services. Coleman’s section also co-ordinated interception in the Middle East with interception in Britain.
Accurate interception was essential when attacking Enigma, since hours could be lost because of a single wrong letter or call sign, or even a mistake in measuring the frequency. Hut 6 was unable to break Yellow for 5 May 1940, because of a single incorrect letter in the intercept, although the Poles solved it on 7 May. When resourcesallowed, radio nets were therefore often covered by two (or sometimes even six) sets to ensure that signals were precisely recorded. Only first-rate operators could deal with very faint signals coupled with interference, and drifting or split frequencies, but they were still in short supply even in December 1942. Hut 6 estimated that only about one third of the operators then at Beaumanor and Chicksands were first-rate, and another third, second-rate. Taking a burst of Morse from ‘a distant signal underneath the cacophony of different Morse transmissions, a diva singing grand opera in German, [and] a high-speed Morse transmission’ required a very high degree of skill.
Breaking Red was Hut 6’s most important task throughout the war, as can be seen from the number of radio receivers allocated to intercepting it: in July 1941, sixty-eight sets were taking Red – over half the 119 sets in Britain tasked on Enigma, although the proportion had declined slightly, to about 35 per cent (fifty sets) in October. The average daily traffic on Red of 380
Teile
(message parts) from June to November 1942 was 65 per cent of the total combined traffic (590
Teile)
intercepted on all the Army and SS cipher nets, while the average daily total of the
Luftwaffe
traffic (1,400
Teile)
was over double that of the
Heer
and SS. Red was easy to break once continuity had been established: the net was so widespread that if one crib went down there was a good chance of finding another to replace it. Red’s links to many other
Luftwaffe
keys made it possible to penetrate them by cribs from re-encipherments, which were known as ‘kisses’ in Bletchley Park parlance, because they marked the relevant signals with ‘xx’. Red was also an invaluable source of intelligence on
Heer
topics in North Africa and elsewhere.
Hut 6 solved the
Luftwaffe
Light Blue cipher, which provided intelligence about the
Heer
and
Luftwaffe
in Libya, within about eight weeks of its introduction in January 1941, and read it daily until it went out of service at the end of 1941. The only other
Luftwaffe
cipher intercepted in 1941, Mustard, the field cipher on the eastern front of the
Luftwaffe
Sigint service, the
Funkaufklärungsdienst
(Radio Reconnaissance Service), was solved for twelve days in the late summer, and from April 1942. It proved useful in giving the order of battle of the Soviet Army and Air Force, and by revealing the very considerable insecurity of Soviet ciphers.
In 1942 all
Luftwaffe
Enigma key-lists except Brown were apparently prepared by one man, who often merged differentcomponents of previous keys (for example,
Stecker)
when preparing new key-lists. The April Foxglove keys combined
Luftwaffe
and
Heer
Enigma, but even as late as January 1945, Hut 6 was ‘as short of sets as ever’: minor
Heer
and
Luftwaffe
ciphers were not being intercepted, and no attempt could therefore be made to break them.
The service authorities came to accept Hut 6’s view that Enigma interception was an indivisible problem, and allocated Army sets to
Luftwaffe
traffic, and RAF sets to
Heer
signals. Later, they also relinquished control of tasking the Army and RAF sets. In May 1943 Hut 6’s intercept control section under John Coleman specified the Enigma tasks to be taken by the intercept stations, and the number of sets to be allocated, but the stations remained under the administrative control of their parent services. Coleman’s section also co-ordinated interception in the Middle East with interception in Britain.
Accurate interception was essential when attacking Enigma, since hours could be lost because of a single wrong letter or call sign, or even a mistake in measuring the frequency. Hut 6 was unable to break Yellow for 5 May 1940, because of a single incorrect letter in the intercept, although the Poles solved it on 7 May. When resourcesallowed, radio nets were therefore often covered by two (or sometimes even six) sets to ensure that signals were precisely recorded. Only first-rate operators could deal with very faint signals coupled with interference, and drifting or split frequencies, but they were still in short supply even in December 1942. Hut 6 estimated that only about one third of the operators then at Beaumanor and Chicksands were first-rate, and another third, second-rate. Taking a burst of Morse from ‘a distant signal underneath the cacophony of different Morse transmissions, a diva singing grand opera in German, [and] a high-speed Morse transmission’ required a very high degree of skill.
Breaking Red was Hut 6’s most important task throughout the war, as can be seen from the number of radio receivers allocated to intercepting it: in July 1941, sixty-eight sets were taking Red – over half the 119 sets in Britain tasked on Enigma, although the proportion had declined slightly, to about 35 per cent (fifty sets) in October. The average daily traffic on Red of 380
Teile
(message parts) from June to November 1942 was 65 per cent of the total combined traffic (590
Teile)
intercepted on all the Army and SS cipher nets, while the average daily total of the
Luftwaffe
traffic (1,400
Teile)
was over double that of the
Heer
and SS. Red was easy to break once continuity had been established: the net was so widespread that if one crib went down there was a good chance of finding another to replace it. Red’s links to many other
Luftwaffe
keys made it possible to penetrate them by cribs from re-encipherments, which were known as ‘kisses’ in Bletchley Park parlance, because they marked the relevant signals with ‘xx’. Red was also an invaluable source of intelligence on
Heer
topics in North Africa and elsewhere.
Hut 6 solved the
Luftwaffe
Light Blue cipher, which provided intelligence about the
Heer
and
Luftwaffe
in Libya, within about eight weeks of its introduction in January 1941, and read it daily until it went out of service at the end of 1941. The only other
Luftwaffe
cipher intercepted in 1941, Mustard, the field cipher on the eastern front of the
Luftwaffe
Sigint service, the
Funkaufklärungsdienst
(Radio Reconnaissance Service), was solved for twelve days in the late summer, and from April 1942. It proved useful in giving the order of battle of the Soviet Army and Air Force, and by revealing the very considerable insecurity of Soviet ciphers.
In 1942 all
Luftwaffe
Enigma key-lists except Brown were apparently prepared by one man, who often merged differentcomponents of previous keys (for example,
Stecker)
when preparing new key-lists. The April Foxglove keys combined
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