Churchill's diplomatic eavesdropping and secret signals intelligence as an instrument of British foreign policy, 1941-1944: The case of Turkey

Churchill's interest in secret signals intelligence (sigint) is now common knowledge, but his use of intercepted diplomatic telegrams (bjs) in World War Two has only become apparent with the release in 1994 of his regular supply of Ultra, the DIR/C Archive. Churchill proves to have been a voracious reader of diplomatic intercepts from 1941-44, and used them as part of his communication with the Foreign Office. This thesis establishes the value of these intercepts (particularly those Turkey- sourced) in supplying Churchill and the Foreign Office with authentic information on neutrals' response to the war in Europe, and analyses the way Churchill used them. Turkey was seen by both sides to be the most important neutral power and therefore constitutes the case study for this analysis. The thesis answers the question 'why did Turkey interest Churchill.' by tracing his involvement with diplomatic intercepts back to 1914, and then revealing how the Government Code and Cipher School (GCCS) was empowered to continue monitoring such traffic until 1939, when 'Station X' was established at Bletchley Park (BP). Following two chapters that trace the interwar work of GCCS on the secret diplomatic traffic of most major powers and outline Turkey's place amongst those powers, the thesis concentrates on four events or processes in which Churchill's use of diplomatic messages played a part in determining his wartime policy, which was sometimes at odds with that of the Foreign Office. Chapter four answers the question what use did Churchill and the Foreign Office make of bjs to persuade Turkey to join the Allies between 1940 and 1942. Chapter five offers a new explanation of why the Adana conference of January 1943 produced little change in Turkish foreign policy. Chapter six explains the Dodecanese defeat of 1943 in the light of the signals intelligence Churchill was reading. Chapter seven shows the results at GCCS in London of the theft of secret Foreign Office papers in Ankara from November 1943: whether actual bjs were included in these papers; how they were received in Berlin and subsequently in Berne, Washington and London; and how they led to a breakthrough in reading the German diplomatic cipher, too late to be useful to Churchill. The thesis concludes by emphasising the personalised nature of wartime diplomacy and re-iterates the reasons why Churchill and the Foreign Office attached such importance to their 'Most Secret Sources', though their availability to historians requires little change to the record.