Section V’s Early Growth and Use of ULTRA
Section V – hereafter referred to as MI6(V) - at that time based at Glenalmond, was responsible for building a complete picture of the enemy intelligence services in foreign countries – personnel, organization, communications and plans. While MI6(V) was at this point its own main customer (in contrast to most other sections within the service), it was also tasked to keep MI5 briefed on the general picture abroad, and specifically to provide advanced information on any planned operations against Britain territory, as well as carrying out enquiries abroad arising from MI5’s work at home. In the sometimes acrimonious infighting for control of MI6(V) and ULTRA/ISOS material, MI5 made the somewhat tenuous argument that they should be regarded as the Section’s primary customer, and therefore be given access to all information obtained by MI6(V). Col Cowgill, as head of the section, strenuously defended his position that MI5 should receive material only where it impinged upon British or Imperial territory.
ISOS material, mentioned above, was an abbreviation for Abwehr signals decrypted and disseminated as “Intelligence Service, Oliver Strachey” material. Strachey was a leading Abwehr cryptanalyst at Bletchley. Hand ciphers used by the Abwehr for communications with its agents were first broken in March 1940, thanks to access to the code given by the Abwehr to the double agent SNOW, and ISOS was issued to government customers from July 1940. (Jason Webster in his book “The Spy with 29 Names” claimed that ISOS was online from April 1940, perhaps referring to the original breakthrough, but the regular dissemination of ISOS began later) [14]. This intelligence flow increased significantly from late December 1940, when the hand cipher of the main Abwehr group was broken.
The decrypts issued as ISK material – “Intelligence Service, Knox” (for Dillwyn Knox), were from intercepted Enigma machine signals used on the main links from Berlin to its stations abroad. [15] These were not broken until 25 December 1941, thanks in part to the information gained from the decryption of the hand ciphers, and were then codenamed ISK. [16]. Within OSS/X-2 the two sets of decrypts were codenamed PAIR and ICE, but within the British Intelligence community both were generically known as ISOS. This term also was used for other types of decrypted materials, such as ISOSICLE (which was a series of decrypts of Sicherheitsdienst traffic, issued by Bletchley from May 1941); ISTUN (material from the cipher of the Abwehr teletype system codenamed TUNNY, which was broken in early 1942); and GGG (cipher traffic between Berlin and the Abwehr stations around the Straits of Gibraltar, broken February 1942). [17] Between July 1940 and June 1945 a total of 268,107 intercepts were handled: 97,340 ISOS; 140,662 ISK; 13,047 ISOSICLE; and 17,058 other categories. [18]
Bletchley Park, home of the Government Code and Cypher School (GC&CS), was at this time subordinate to MI6 and was in close liaison with MI6(V). The material from these intercepts was, according to Tim Milne, disseminated directly to a number of organizations, including MI6 and MI5. Anxiety was expressed by members of MI5 at any potential interruption in the flow of this traffic, pointing to the value of the material in the running of the MI5 CEAs. The head of MI6(V) was properly reluctant to share raw information from and about MI6's own agents abroad, but not restricting ISOS material generally. He had no desire to provide MI5 with possible ammunition to be used in the ongoing battle for control of CE abroad. Cowgill therefore restricted for a short time dissemination of ISOS decrypts which named or referred to MI6 agents and intelligence operations, this material being given the codename ISBA. [19]
After this restriction was made known unofficially to MI5 (by a dissident MI6(V) officer, Hugh Trevor-Roper, who disapproved of restricting the dissemination of ISOS material), an agreement was reached that Cowgill would provide the ISBA material to two senior MI5 officers. An official report on the MI6(V) use of ISOS pointed out that, while MI5 and service departments received the ISOS texts, “no action on them was permissible without prior reference to Section V.” [20] This may have been the main reason why MI5 tended to chafe at the fact that MI6(V) controlled the ISOS material, since they clearly did have access to ISOS traffic.
Milne described another “potential task” for MI6(V) at this time, besides acting as a conduit of ISOS to MI5, as something
“scarcely yet embarked upon…to initiate or encourage whatever steps could be taken abroad to stifle enemy espionage organizations and activities on the spot, through diplomatic or other means.” [21]
MI6(V) generally used ISOS to act against personnel of the enemy services; to check on leakages of our own war secrets; and to control deception. Action against agents entering Allied territory under MI5 control could include arrest and interrogation and turning the agents, and in neutral countries action might be restricted to denunciation to the local authorities. An MI6 report stated that between 1940 and 1945 the enemy sent 112 agents to the UK who were captured, seventeen of whom were caught exclusively because of ISOS, and thirty-five of whom were reflected in ISOS decrypts but their arrests were not attributable to ISOS. In neutral countries the physical capture or elimination of agents was often more troublesome than was worthwhile, so denunciation either through diplomatic channels or by making it known through “a timely word either in the ear of a friendly neutral official or even…in that of the agent himself” would usually suffice to secure the removal of the agent from that country.
Every leakage report seen in ISOS material was investigated, and apart from the CICERO case in Ankara, none involving British Embassies and Consulates proved true. [See Footnote c] Most of the reports which supposedly derived from neutral journalists, businessmen or government official who had visited Britain or the USA also proved false. The need to act on ISOS material in foreign countries meant that MI6(V) had to place staff in critical spots, and the staff had to be ISOS-indoctrinated. This was a slow process and priority of posting was allocated according to the needs of MI6 rather than MI5 or SIME, which meant that the corresponding communication channels for distributing ISOS had to await the expansion of MI6(V).
ISOS proved an invaluable guide into the minds and perceptions of the enemy, which permitted the Allies to plan and carry out a successful policy of deception. ISOS revealed what the GIS wanted to find out, their intentions and what they believed the Allies intentions were. By studying what information the GIS was receiving, true and false, the Allies were able to judge the likely reception of the GIS to the deception stories they wished to deploy. Through ISOS, MI6(V) could also often monitor the movements and actions of their double agents (DAs) to be reassured as to their safety, discretion and good faith. Finally, MI6(V) could see what the GIS thought of the agent, his potential access, any questions they might have regarding his motives or conduct, and “most important, we knew how they assessed his information”. [22]
Boyle in “The Climate of Treason” alleged that “to a large extent, the counter-espionage activities of MI6 were a hollow pretense” being made “partly redundant” by the codebreakers at Bletchley, but still necessary in order to protect “the security of the source”. [23] This view fails to consider that much of the ISOS material required further research to become understandable, even after decryption. For example, codenames and numbers, often several, were used for Abwehr agents and officers, and codenames were sometimes used for technical material and locations. Former MI6(V) officer Kenneth Benton wrote an article [See Footnote d] which explained in detail how the MI6(V) staff abroad was used to provide information vital to the understanding of the ISOS messages, such as identifying people on specific flights or staying at hotels on dates when agents were known to have flown or been resident. Identified Abwehr officers and agents might be kept under surveillance if it were learned from ISOS that they were to meet with unidentified members of the Abwehr’s organization. ISOS information needed to be further developed by MI6(V) staff abroad and constantly re-interpreted by the MI6(V) desks in order to gain maximum understanding from it.
Section
