Michigan War Studies Review
Reviews, surveys, original essays, and commentary in the field of military studies.
2020-065
16 July 2020
Review by Alan Malpass, Bishop Grosseteste University
The Walls Have Ears: The Greatest Intelligence Operation of World War II
By Helen Fry
New Haven: Yale Univ. Press, 2019. Pp. xiv, 319. ISBN 978–0–300–23860–0.
Descriptors: Volume 2020, 20th Century, World War II, Intelligence Print Version

At the end of the 1965 hit British film Operation Crossbow (dir. Michael Anderson), an extremely fictionalized account of the attack on the German V-weapons program, Winston Churchill congratulates Duncan Sandys on the destruction of a rocket facility in southern Germany. Sandys remarks that the names of the valiant agents crucial to the success of the mission "will never be known." Even less well known today is the covert listening operation that confirmed the existence of the V-2 launch site at Peenemünde, the target of the actual Operation Crossbow in 1943. Thankfully, in her latest book, The Walls Have Ears, military historian Helen Fry (Univ. College London) examines this cunningly choreographed British intelligence operation, which involved teams of listeners eavesdropping on German POWs at special sites fitted with M (miked) Rooms.


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Fry has written extensively on the Second World War, focusing on intelligence, POWs, and German and Austrian refugees; she has also acted as historical consultant on several TV documentaries. In The Walls Have Ears, which adapts aspects of her previous works,[1] she draws on declassified files at the National Archives, as well as interviews and memoirs, to survey the intelligence gathered by MI-19 secret listeners, the methods used to acquire it, and the lives of the POWs who were bugged.

The book is structured chronologically. Months before the war, British intelligence agencies agreed to form a unit to listen in on enemy POWs. It was led by Thomas Kendrick, an MI-6 spymaster who handled espionage networks in Europe. Named the Combined Service Detailed Interrogation Centre (CSDIC), it worked within MI-19 and was based at the Tower of London before moving to Trent Park at Cockfosters. The high value of the intelligence it gathered by listening to German POWs was quickly realized and the unit was expanded to sites at Latimer House and Wilton Park. Many high-ranking generals and around ten thousand rank-and-file POWs were channeled through these sites by the end of the war. Fry provides technical details of how these sites were fitted to record prisoners' conversations, the apparatus they used, and the recruitment of listeners and stool pigeons. The bugging operation was extensive and cunning. Anything and everything was fitted with microphones,

from the light fittings to the fireplaces, plant pots, behind the skirting boards, under floorboards of the bedrooms, and even the trees in the gardens.… A British officer would even sit on a bench outside for a chat … carefully placed near a hidden microphone so their conversations could be recorded. (106)

Individual chapters outline the intelligence gathered in this manner, including information on the Enigma machine, the movement and tactics of German battleships, numbers of operational U-boats, new aircraft and navigational technologies, the state of morale in Germany, and the work of resistance movements. In a chapter on "Rocket Science," the author asserts that intelligence on the V-weapons program alone "proved the value of the whole MI-19 operation and more than justified the three sites" (166).

Several chapters offer insights into the everyday lives of the German generals held at Trent Park. The first were captured in 1942, including Ludwig Crüwell and Ritter von Thoma. Fry likens the camp atmosphere to the "Mad Hatter's Tea Party" and discusses the enmities between the pro- and anti-Nazi groups as well as their reactions to events such as D-Day, Operation Valkyrie (the July 20th [1944] plot to assassinate Hitler), and Germany's ultimate defeat.

The final chapters concern intelligence on atrocities. From 1943, substantial evidence was collected regarding concentration camps, mobile gas trucks, and eyewitness accounts of mass executions in the East. The secret listeners recorded discussions between generals that exposed their knowledge and involvement. In May-June 1945, the Joint Intelligence Committee discussed the use of the transcripts to prosecute war criminals. The new head of MI-19, Lt. Col. Sam Derry, argued against publicly divulging M Room methods in order to protect the future of CSDICs and ongoing actions, like Operation Epsilon at Farm Hall near Cambridge, where they eavesdropped on conversations of chief German atomic scientists. Fry explains that looming Cold War tensions with the Soviet Union made Derry determined to secure the workings of the CSDICs as prized sources of intelligence. Use of M Room intelligence in postwar trials was therefore limited to briefing interrogators and cross-examiners, and guiding investigations. Consequently, Nazi generals were not prosecuted based on their admissions of guilt recorded by the secret listeners. This highly questionable decision was criticized by members of the intelligence community at the time. Fry herself refrains from any censure, noting that the decision "highlights the moral dilemmas facing intelligence chiefs" (258).

Duping POWs into talking candidly was crucial to the operation. The consistent conduct of formal interrogations was key. German POWs knew the sites were interrogation centers and expected to be questioned after their capture. They were put through rigorous interrogation so they would not suspect their rooms were wiretapped. Back in their cells, blissfully unaware POWs discussed facts they had kept from interrogators and joked about how little the British knew.

Fry calls the decision to move German generals to Trent Park "one of British intelligence's most cunning deceptions of the war" (104). Expecting to be kept in standard camps, to their pleasant surprise,

the generals found themselves living a life of relative luxury at, they believed, the generous behest of the King and according to their status as military commanders—and this played right into their sense of self-importance. Their every need was catered for and they began to relax into their surroundings. Trent Park could be likened to a traditional privileged, exclusive gentleman's club in central London. (104)

This was not, of course, a matter of class sentiments, but part of a calculated plan to create an atmosphere that encouraged the generals to talk:

The most important dimension of the scenario created at Trent Park was that it provided British intelligence with the unguarded conversations of Hitler's top military commanders. The place was, in essence, nothing more than a location to garner secrets—everything else was a façade, a theatrical stage set created by Kendrick and his immediate boss, Major Arthur Rawlinson. The personal mannerisms of the generals were noted by MI-19 on their personal files to build a physical and psychological profile of each of them. Understanding their characters would enable British intelligence to make the most of "the guests" (as they were called in the intelligence reports) and create scenarios which would facilitate unwitting disclosure of the closely protected secrets of the Third Reich. (107)

The intelligence officers befriended the generals. They took walks together around Trent Park's grounds and made trips to London, sometimes having lunch on the Strand. Kendrick occasionally invited them to his Surrey home for tea. Lord Aberfeldy, the welfare officer who looked after and entertained the generals, was in fact an intelligence officer "exceedingly good at acting" (107) and not second cousin to the King. Some generals required more creative deceptions before they would divulge information. Hermann Ramcke was reserved in speaking with other generals and revealed little during interrogation. Several bottles of cognac and a fake press release announcing that Hitler himself had awarded him a medal loosened him up and he revealed all.

Chapter 8 switches perspective to the other side of the wall and the work of the "Secret Listeners." Those recruited to work in the M Room were fluent not only in standard German but also in its regional dialects. They had to be knowledgeable of German weaponry and military hierarchy, and have sufficient grasp of the war situation to recognize information that Kendrick and his superiors were keen to have. As the number of native Britons dried up, German-speaking refugees serving in the Pioneer Corp were recruited. Those who had fled Nazi Germany and the Gestapo in the 1930s now secretly heard the conversations of German officers. The refugees among the listeners had to retain their emotional detachment. With friends and family in occupied Europe, they found conversations about atrocities particularly distressing.

Fry emphasizes the role of women in the operation. As the unit expanded, more were recruited to transcribe conversations and perform key administrative duties like categorizing intelligence to ensure it went to the appropriate services. For example, Catherine Townshend was selected to oversee MI-19e at Wilton Park, which involved running the technical side of M Room operations, because she was considered the most knowledgeable and able candidate for the task. For Fry, her appointment

highlights an important point—that the intelligences services were often decades ahead of civilian life in appointing the right person for the job, irrespective of gender. Consequently, during the Second World War, women played vital roles within the intelligence world because they developed the necessary skills for a particular job. (94)

The strength of this highly readable account of an overlooked episode of British intelligence lies in its discussions of the people who were listening and the imaginative methods used to deceive the enemy into talking openly. That said, the book does not significantly advance our understanding of the value of intelligence gathering. The limited bibliography omits seminal studies of the CSDIC in both the early and late periods of the war.[2] Nor is there any mention of previous studies of the specific intelligence gathered on the Luftwaffe[3] and the Holocaust.[4] The relationship between the intelligence and military strategy is left unclear and the bugging operation is not situated within the wider context of wartime intelligence gathering. Fry neglects to indicate that the British POW interrogation system was a global in scope, with CSDIC branches located in the Mediterranean and the Middle East. We learn nothing about the part Canada played as a POW intelligence partner to the British and Americans.[5]

Nonetheless, The Walls Have Ears does a great service by clarifying the value of the work of Kendrick and the secret listeners in gathering human intelligence from enemy POWs, a subject that has neither generated the sort of voluminous literature devoted to Ultra and Signals Intelligence and Bletchley Park, nor occupied a prominent place in the British memory of the war. Indeed, those involved, including Kendrick, were sworn to secrecy and never spoke of their work. Helen Fry has written a fitting tribute to the men and women who contributed so significantly to the war effort. Her book will interest and instruct general readers intrigued by the clandestine side of the war, as well as students and scholars of wartime intelligence, POWs, and the Second World War.

[1] Esp., The M Room (2012) and Spymaster: The Secret Life of Kendrick (2014), both published under Amazon's CreateSpace imprint.

[2] See, respectively, Kent Fedorowich, "Axis Prisoners of War as Sources for British Military Intelligence, 1939–42," Intelligence and Nat'l Security [hereafter, INS] 14 (1999) 156–78; and Falko Bell, "One of Our Most Valuable Sources of Intelligence: British Intelligence and the Prisoner of War System in 1944," INS 31 (2015) 556–78.

[3] See Kevin Jones, "From the Horse's Mouth: Luftwaffe POWs As Sources for Air Ministry Intelligence during the Battle of Britain," INS 15 (2005) 60–80.

[4] See Stephen Tyas, "Allied Intelligence Agencies and the Holocaust: Information Acquired from German Prisoners of War," Holocaust and Genocide Studies 22 (2008) 1–24.

[5] See Jean-Michel Turcotte, "An Important Contribution to the Allied War Effort: Canadian and North Atlantic Intelligence on German POWs, 1940–1945," INS 43 (2019) 289–306.

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