in the early years of the war was not just about the German military secrets revealed through Enigma. Even harder to break than the Enigma machine had been a German teleprinter on-line cypher machine known as ‘Tunny’, used by the German High Command to produce ‘Fish’ messages. On-line cypher machines were especially challenging because they were automatic, and sent a continuous stream of text, much of it dummy material, sometimes offering no obvious start or end points to each message. This went some way to eliminating another weakness of the Enigma machine – its operators, who were prone to human error. To address the problem of ‘Tunny’, the British later built ‘Colossus’, one of the earliest general-purpose electronic machines, and perhaps the first device that might be described as a ‘computer’. Conceived by Professor Max Newman and then developed by Tommy Flowers from the British Post Office research facility at Dollis Hill, this was one of the supreme technical achievements of the war.[41]
The achievements of the civil side of GC&CS have often been neglected. By 1940 it was analysing not only the diplomatic codes and cyphers of the Axis powers, but also those of more than twenty other countries. These included the Soviet Union, which did not enter the war until it was attacked by Germany on 22 June 1941. The diplomatic communications of quarrelsome allies such as the Free French, or important neutrals such as the Turks and the Spanish, proved as interesting and as useful as those of Germany. Moreover, the traffic of Germany’s allies, such as Japan, could shed a penetrating light on the mindset of Berlin. Throughout 1941 Hitler held regular meetings with Baron Oshima, the Japanese Ambassador in Berlin, often referred to as ‘Hitler’s Japanese confidant’. Japan had its own complex cypher, known as ‘Magic’, produced by a machine called ‘Purple’, and Oshima used it to send detailed accounts of his long conversations with Hitler to Tokyo. ‘Magic’ had been broken by the Americans, and early Anglo–American cooperation on code-breaking ensured that all this was being read in London. Remarkably, Berkeley Street was also working on the cyphers of the United States, which did not join the war until the Japanese attack on Pearl Harbor on 7 December 1941.[42]
The dramatic events of 1941 transformed the course of the Second World War. Although the Battle of Britain had staved off the possibility of a German invasion, by the summer of 1941 Britain had been fighting for almost two years without a major victory. Therefore, Hitler’s bizarre decision to invade Russia in June 1941, which required the legions of the Wehrmacht to turn east, provided a welcome breathing space. After Japan’s attack on Pearl Harbor, Britain, the United States and Russia found themselves ranged together against the Axis in what was soon called the ‘Grand Alliance’. Welcome as this was, a genuine world war created new dilemmas for the denizens of Bletchley Park, who now confronted the ticklish issue of large-scale Allied cooperation in the business of code-breaking.
… there is no better analogy than the schoolboy with his stamp collection.
GC&CS, discussing intelligence cooperation with the Russians in 1943[1]
The most secret aspect of Bletchley Park’s wartime work was its dealings with friends and allies. Many have pondered whether the British attacked Soviet codes and cyphers during the Second World War. The official history of British intelligence insists that Churchill ordered this activity to stop in June 1941, following Hitler’s invasion of the Soviet Union, since Moscow had suddenly become an ally.[2] However, it is now clear that this is quite untrue. At the end of October 1941, intelligence chiefs were actually discussing the expansion of the sigint organisation in India, which was then dealing with ‘material from Russian, Persian and Afghan sources’. Remarkably, it was not yet working on German traffic.[3] Moreover, in January 1942, and again in early 1943, the British and the Americans were discussing the mutual exchange of intercepted material from ‘Slavic nations’.[4] Soviet cyphers had been the core business for Britain’s interwar code-breakers, and work on this material never stopped completely during the Second World War.
To understand why, we must cast our minds back to the approach of the war. During the 1930s, GC&CS continued to follow the traffic of the Comintern even after other Soviet systems were lost. This revealed persistent efforts to subvert the British Empire in locations such as India, Malaya and Hong Kong. Indeed, the Soviet Union appeared to be in league with Germany after the Nazi–Soviet Pact of August 1939. It is often forgotten that Poland was invaded by Germany and the Soviet Union together. For a nightmare period between August 1939 and June 1941, many suspected that Germany, Italy, Japan and the Soviet Union would act in uneasy concert, dividing the spoils of the world between them. This was precisely the plan that Germany’s Foreign Minister, Baron Joachim von Ribbentrop, was trying to press upon his irascible master. However, in the end Adolf Hitler’s racist outlook could not tolerate the idea of alliance with the Slavic peoples, and he had always declared his desire for ‘Lebensraum’ in the east.[5]
Throughout this dangerous period, before Hitler and Stalin turned upon each other, the Soviet Union remained a key intelligence target. SIS even organised a secret squadron to conduct aerial reconnaissance of possible bombing targets deep inside southern Russia, notably the oilfields. GC&CS developed close relations with code-breakers in the Baltic states who were also working on Soviet codes. A month after the outbreak of war with Germany, Clive Loehnis, a naval officer at GC&CS (who would become Director of GCHQ in the 1960s), told Alastair Denniston that additional premises were needed to cope with the increase in the interception of Soviet military traffic, so new buildings were erected at Scarborough.[6] With the military chiefs keen to ‘get cracking on Russian traffic’, Denniston began a unique and profitable experiment. In 1939 GC&CS sent a party of British sigint operators to Sweden to work secretly out of the British Embassy in Stockholm, where there was better radio reception from Russia. The creation of this forward listening station was fortuitous, since Stalin embarked on the Winter War against Finland in November 1939, and GC&CS enjoyed a front-seat view of the whole proceedings.[7]
John Tiltman remained the key figure in the effort against Soviet communications. A colonel in the King’s Own Scottish Borderers, he was noted for his smart uniform, which included tartan trews. However, as the war progressed he came under the influence of the spirit of Bletchley Park, and was often seen in a baggy pullover and green corduroy slacks.[8] One of his first duties was to visit Helsinki to conclude a deal with the talented Finnish code-breakers. Britain funded the expansion of the Finnish cryptographic bureau, and supplied it with the latest equipment in return for material on the Soviets. In March 1940, after imposing a series of humiliating defeats on the Soviets, the Finns signed the Moscow Peace Treaty, ceding about a tenth of their territory.[9] The sigint deal with the British was unaffected, and indeed in September 1940 its scope was expanded during a visit by Admiral Godfrey, the Director of Naval Intelligence. According to an internal GC&CS history written after the war, ‘The Finns had agreed to supply us with copies of all their intercepts and cryptographic successes, provided that we did the same.’ Preceding the agreement with the Americans by more than a year, this was perhaps Britain’s first comprehensive sigint alliance.[10]
By March 1940, the interception of Soviet traffic was big business. For the first time, collection began in the Middle East, at Sarafand in Palestine, although it was still sent to India for analysis. Soviet traffic was also being taken at Ismailia in Egypt and Dingli in Malta. Meanwhile, in Hong Kong, other British sigint operators were also listening to the Soviets before they packed up their equipment to move to Singapore in anticipation of a Japanese attack. The surge of Soviet traffic meant changes were required at GC&CS, where an inter-service Soviet section was created to work in close conjunction on naval, military, air, diplomatic and commercial material. After the fall of France in the summer of 1940, evacuated French cryptographers joined the effort on Soviet traffic at GC&CS. A Polish section, based at Stanmore on the northern fringes of London, soon discovered that it was able to listen in to Soviet traffic as far away as Ukraine.[11]
Ultra had provided Bletchley Park with an intimate picture of the build-up