It was in the realm of signals intelligence (SIGINT) that Churchill’s support of the intelligence services paid the biggest dividends. The unprecedented successes gained by British intelligence during the war were caused largely by the herculean efforts of the code-breakers at GC&CS, based at Bletchley Park. In the course of the war, Bletchley Park would come to preside over mass-espionage on an industrial scale. In May 1941 Churchill received a top-secret request from Bletchley Park begging for more resources. He was so perturbed that he demanded ‘Action this Day’, and instructed his military assistant, General Hastings ‘Pug’ Ismay, to give GC&CS all the resources it needed and to report that this had been done. In December 1940 Bletchley Park had managed, with the assistance of Polish code-breakers, to crack the first of the famous German Enigma codes. With the resources that Churchill now threw behind it, GC&CS expanded rapidly: by 1943 its code-breakers were reading on average 3,000 German communications per day. These decrypts were codenamed Ultra, but were also known as ISOS, standing for ‘Intelligence Services Oliver Strachey’ (ISOS), named after a high-ranking official at GC&CS, and more generally were termed ‘Most Secret Sources’ (or MSS for short). The Ultra decrypts were passed by SIS, which had formal control over GC&CS during the war, directly to Churchill himself on an almost daily basis. Ultra provided such accurate and rapid ‘live’ intelligence that some German communications from the Eastern Front or the deserts of North Africa actually arrived on Churchill’s desk in London before they reached Hitler in Berlin. Bletchley Park code-breakers also acquired chilling ‘real time’ messages about the Holocaust. As early as 1941, intercepts of low-grade German traffic from the Eastern Front were revealing to Bletchley Park what, with hindsight, we can see was the evolution of the Nazi ‘Final Solution’ – the mass murder of European Jews and other supposed racial subhumans (Untermenschen). There is some existing but disputed evidence that the British and US governments refused to release what Bletchley Park had discovered about the Holocaust because to do so would have jeopardised the Ultra secret. On present evidence, it is impossible to state whether this was the case or not.15
Over 12,000 people are thought to have worked at Bletchley Park, and their voluminous Ultra decrypts contributed to Allied military successes in a number of areas. The leader of British forces in North Africa in 1942, General Sir Bernard Montgomery, was provided with a stream of high-grade Ultra decrypts that revealed the location of his opponent Erwin Rommel’s Afrika Korps. The decrypts flowing to Montgomery were so accurate that after the war the JIC worried that when the history of the North African campaigns came to be written, historians would realise that he had some kind of foreknowledge of Rommel’s movements, and would be able to piece the puzzle together. As it turned out, the JIC gave historians far too much credit – the Ultra secret remained hidden for years after the war. We now know that the decrypts assisted Montgomery’s Eighth Army in its famous victory in the summer of 1942 at El Alamein, once an obscure port on the edge of the Egyptian desert, which was a major turning point in the Allied campaign in North Africa. By May 1943 Montgomery’s ‘desert rats’ had effectively driven Rommel’s Afrika Korps into the sea in Tunisia. Bletchley Park’s Ultra decrypts also produced direct benefits for the Allies in the Battle of the North Atlantic: they revealed the locations of German U-boats, allowing the Admiralty to manoeuvre supply convoys away from danger, bring shipping losses down to bearable levels, and contributed to Allied victories in the Battle of Cape Matapan (March 1941) and the Battle of the North Cape (December 1943).16
Ultra decrypts likewise made possible MI5’s now-legendary ‘Double Cross System’, the process by which every German agent in Britain was identified, and many of them turned into double agents. It was only after Ultra came on-line in December 1940 that MI5 could establish conclusively whether any unidentified German agents were operating in Britain, and also, crucially, whether the disinformation that MI5’s double agents were passing back to Germany was being believed by the German High Command. The MI5 officer T.A. ‘Tar’ Robertson, who was in charge of Section B1a within MI5, responsible for running double agents, would later describe how Ultra decrypts allowed MI5 to see whether the files of its enemies were being stocked with the exact information that MI5 desired. In several cases, MI5 watched with pride as its disinformation was passed by the Nazi intelligence services across Europe and beyond. The magnitude of these successes was later summarised by Sir John Masterman, the head of MI5’s wartime deception committee, who noted that during the war Britain ‘actively ran and controlled the German espionage system in this country’.17
Churchill later reflected on the value of the intelligence produced by Bletchley Park and the secrecy of its operations, describing its code-breakers as ‘the geese that laid the golden eggs but never cackled’. Some historians, including F.H. ‘Harry’ Hinsley, who worked as a junior official at Bletchley Park and who later became the editor of the magisterial official history of British intelligence in the Second World War, have suggested that the intelligence produced by Bletchley Park was so valuable that it shortened the war by up to two years, saving countless lives on both sides. More recently, doubt has been cast on this claim, with historians arguing that the Second World War was really a war of matériel production, and that once the Soviet Union and the United States entered the war, in June 1941 and December 1941 respectively, victory for the Allies was assured. Although counter-factual ‘what if’ postulations can produce endless debates, the reality was that, if the war in Europe had not ended in May 1945, the Allies would have dropped an atomic bomb on Germany – which was the original target for the bombs dropped on Japan in August 1945.
A-FORCE: THE BIRTH OF BRITISH STRATEGIC DECEPTION
The idea of strategic deception – that is, providing false information to misguide an enemy’s strategy – was put to best use by Allied forces in Europe, but it was not originally conceived there. During the so-called phoney war, between the outbreak of war in September 1939 and the Battle of Britain in the summer of 1940, the Middle East was the only theatre where British forces were directly fighting Axis forces, and it was there that innovative uses of intelligence for modern military affairs were born. Before either MI5 or SIS had begun to envisage the idea of strategic deception, it was being pioneered by a small, crack intelligence outfit attached to the Cairo-based staff of the British commander in the Middle East, General Archibald Wavell. Wavell was one of the best-educated generals in British military history, a quiet, scholarly type who liked to write poetry in his spare time and had lost an eye in the Great War. He knew the history of Lawrence of Arabia well, and valued the use of intelligence in war. The unit he established was known as ‘A-Force’, and the man he placed in charge of it was a brilliant military intelligence officer, Lt. Col. Dudley Clarke, who came up with a number of ingenious deception ploys. In Clarke’s view, it was possible to do more than prevent secrets reaching an enemy’s intelligence service (counter-espionage): secrets obtained through counter-espionage could also be used to deceive an enemy’s strategy (strategic deception).18
In 1940 Clarke recruited a young officer, Jasper Maskelyne, who came from a long succession of famous stage magicians and conjurors, to help him build an entire false city out of plywood in the Egyptian