Stanley, we were sure, must be Philby. Golitsin had heard the code name Stanley, and associated it with KGB operations in the Middle East, but there was no proof of this in the traffic. Hicks, therefore, was almost certainly Burgess because of the reference to the ARGENTURA, and because of a veiled reference to Hicks' temperament. Johnson was probably Blunt, although again there was no proof of it in the traffic. But the identity of the five other spies remained a mystery. Maclean was obviously not one of these, since he was in Washington in September 1945. The consequences for the Mitchell investigation were obvious. Any one of the five unidentified cryptonyms could be the spy inside MI5. I remember wondering, as I read the tantalizing decrypts, how on earth anyone at the top of MI5 had slept at night in the dozen years since they were first decrypted.
Perhaps the most extraordinary thing in the whole VENONA story was the fact that it was closed down on both sides of the Atlantic in 1954. After the initial surge of activity in the late 1940s and early 1950s, and the rash of prosecutions which followed, cryptanalytical progress slowed to a virtual halt. Hand matching had reached the limitations of the human brain, and computers were not then powerful enough to take the program much further. There was another reason too; in 1948 the Russians began to alter their code procedures worldwide, removing all duplicated pads. The last casualty of this was the Australian VENONA operation, which had been making so much progress that the British and Americans were virtually reading the Russian ciphers continuously as the messages were produced. The Australians were never told at the time but were brought into it some years later, although when the extent of Soviet espionage penetration, especially of the Department of External Affairs, became apparent, they were provided with the intelligence in bowdlerized form, and it led to the establishment of ASIO (Australian Security Intelligence Organization) with MI5's help.
The reason for the change in Soviet codes became apparent in the early 1950s. The secret of the break had been leaked to the Russians by a young Armed Services Security Agency clerk, William Weisband. In fact, Weisband did not know the extent of the Russian mistake and it was only when Philby was indoctrinated in 1949 that they knew the breadth of their disaster, although other people, such as Roger Hollis, were indoctrinated in 1948, when the match suddenly ceased in Australia after he returned from organizing the setting up of ASIO. Although the duplicate one-time pads were withdrawn, the Russians could do nothing to prevent the continuing work on the traffic they had already sent up until 1948. But thanks to Philby's posting to Washington in 1949, they were able to monitor the precise progress that was being made. Once the Russians knew the extent of the VENONA leak, and the technical difficulties of finding more matches multiplied, it was only a matter of time before priorities moved on. In 1954 most of the work was closed down.
Years later, I arranged for Meredith Gardner to visit Britain to help us on the British VENONA. He was a quiet, scholarly man, entirely unaware of the awe in which he was held by other cryptanalysts. He used to tell me how he worked on the matches in his office, and of how a young pipe-smoking Englishman named Philby used to regularly visit him and peer over his shoulder and admire the progress he was making. Gardner was rather a sad figure by the late 1960s. He felt very keenly that the cryptanalytical break he had made possible was a thing of mathematical beauty, and he was depressed at the use to which it had been put.
"I never wanted it to get anyone into trouble," he used to say. He was appalled at the fact that his discovery had led, almost inevitably, to the electric chair, and felt (as I did) that the Rosenbergs, while guilty, ought to have been given clemency. In Gardner's mind, VENONA was almost an art form, and he did not want it sullied by crude McCarthyism. But the codebreak had a fundamental effect on Cold War attitudes among those few indoctrinated officers inside the British and American intelligence services. It became the wellspring for the new emphasis on counterespionage investigation which increasingly permeated Western intelligence in the decades after the first break was made. More directly, it showed the worldwide scale of the Soviet espionage attack, at a time when the Western political leadership was apparently pursuing a policy of alliance and extending the hand of friendship. In the British traffic, for instance, most of the KGB channel during that September week was taken up with messages from Moscow detailing arrangements for the return of Allied prisoners to the Soviet authorities, groups like the Cossacks and others who had fought against the Soviet Union. Many of the messages were just long lists of names and instructions that they should be apprehended as soon as possible. By the time I read the messages they were all long since dead, but at the time many intelligence officers must have been struck by the sense that peace had not come in 1945; a German concentration camp had merely been exchanged for a Soviet Gulag.
In 1959, a new discovery was made which resuscitated VENONA again. GCHQ discovered that the Swedish Signals Intelligence Service had taken and stored a considerable amount of new wartime traffic, including some GRU radio messages sent to and from London during the early years of the war. GCHQ persuaded the Swedes to relinquish their neutrality, and pass the material over for analysis. The discovery of the Swedish HASP material was one of the main reasons for Arthur's return to D1. He was one of the few officers inside MI5 with direct experience of VENONA, having worked intimately with it during the Fuchs and Maclean investigations.
There were high hopes that HASP would transform VENONA by providing more intelligence about unknown cryptonyms and, just as important, by providing more groups for the codebook, which would, in turn, lead to further breaks in VENONA material already held. Moreover, since powerful new computers were becoming available, it made sense to reopen the whole program (I was never convinced that the effort should have been dropped in the 1950s), and the pace gradually increased, with vigorous encouragement by Arthur, through the early 1960s.
In fact, there were no great immediate discoveries in the HASP material which related to Britain. Most of the material consisted of routine reports from GRU officers of bomb damage in various parts of Britain, and estimates of British military capability. There were dozens of cryptonyms, some of whom were interesting, but long since dead. J.B.S. Haldane, for instance, who was working in the Admiralty's submarine experimental station at Haslar, researching into deep diving techniques, was supplying details of the programs to the CPGB, who were passing it on to the GRU in London. Another spy identified in the traffic was the Honorable Owen Montagu, the son of Lord Swaythling (not to be confused with Euan Montagu, who organized the celebrated "Man Who Never Was" deception operation during the war). He was a freelance journalist, and from the traffic it was clear that he was used by the Russians to collect political intelligence in the Labor Party, and to a lesser degree the CPGB.
The extraordinary thing about the GRU traffic was the comparison with the KGB traffic of four years later. The GRU officers in 1940 and 1941 were clearly of low caliber, demoralized and running around like headless chickens in the wake of Stalin's purges of the 1930s. By 1945 they had given way to a new breed of professional Russian intelligence officers like Krotov. The entire agent-running procedure was clearly highly skilled, and pragmatic. Great care was being taken to protect agents for their long-term use. Where there seemed poor discipline in the GRU procedures, by 1945 the traffic showed that control was exerted from Moscow Center, and comparison between KGB and Ambassadorial channels demonstrated quite clearly the importance. the KGB had inside the Russian State. This, in a sense, was the most enduring legacy of the VENONA break - the glimpse it gave us of the vast KGB machine, with networks all across the West, ready for the Cold War as the West prepared for peace.