“And they thought they were secure” could be the epitaph for many failed intelligence operations. Overestimation of the impregnability of codes is a theme that runs through the history of cryptology from the early modern period to the present day. It is often this overconfidence that leads to intelligence successes for the other side. The most spectacular example of this sort of hubris is the story of the German Enigma machine and the British successes in Bletchley Park at decrypting messages encrypted by Enigma known as “Ultra” (for Ultra secret).

It was not until 1974 that the veil of secrecy surrounding the British Ultra operation was lifted and the story was first told by a participant, Frederick Winterbotham, in his book The Ultra Secret. While much has been written about Bletchley Park and the Enigma machine since then, Delusions of Intelligence is the first book to investigate the reasons the Germans failed to realize that their codes had been broken even long after the war ended. It is therefore a welcome and fresh addition to the enormous literature on the Enigma machine.

Ratcliff asks an important question: how could the Allies have conducted this operation for so long without the Germans suspecting how they acquired the information? The book is a close reading of recently released declassified documents primarily at the National Archives in Washington, D.C., but also at the Public Records Office in Kew, England. It is a comparative analysis of the organization and structures of Bletchley Park's code-breaking efforts in Britain and the Germans' military cryptology. She argues that it was British centralization that led to success and Germany's decentralized, fragmented, and hierarchical system that hampered its efforts. The author rightly argues against facile explanations that it was National Socialist ideology that led to German failures.

The book opens with background and an introduction to the Enigma and Bletchley story and draws the reader's attention to the fact that the British created a fiction that an imaginary agent “Boniface” was the source for leaked intelligence information. The first three chapters of the book focus on the Germans: on the new technology of the Enigma, early German intelligence successes, and compartmentalization in German signals intelligence. Another interesting comparison is between the civilian-based British program, where cryptographers were often academics, and the military-based German system that employed few, if any, academics. While we learn that the British cryptographers often had Ph.D.s, biographical information about the German officers, such as Wilhelm Fenner, a chief cryptanalyst in the Germany army, are conspicuously absent. (The Berlin Document Center's Nazi Party files offer rich biographical information.) The author then turns to centralization at Bletchley Park, disguising the real source of the intelligence, the Germans' explanation for Allied success, and Allied communication security. She closes with an analysis of German signals intelligence and the role of science and the machine in the cryptological war, perhaps the weakest chapter because it does not show knowledge of, or engage, the excellent literature on science and technology under National Socialism.

Despite the author's intelligence in presenting the material, this reviewer was not persuaded by the argument that the British centralized efforts led to success. The information presented in the book points to German overconfidence in their technical abilities and to British fear of the Germans' military might. Fear is often not only the mother of invention in cryptology, but also the mother of motivation for success in history. While the Germans realized that the British acquired top-secret German information and that Enigma-generated coded messages were being read, they thought Allied success could only come from a human source or from actually seizing a machine, but not through deciphering the messages themselves.

Although the book provides background on the Enigma machine's history, it takes previous knowledge for granted. For example, the author assumes that everyone knows about the Ultra Secret book and that its author was Winterbotham (no author is mentioned until the second reference on page 108). She also does not engage in discussion about some of the controversies surrounding hiding the true source of the British information or disguising Ultra. It quickly became a popular conception that Winston Churchill sacrificed the city of Coventry to a bombing raid to protect the Ultra secret. According to some scholars, neither Churchill nor Bletchley Park knew about the intended bombing. Ratcliff buries this information in a footnote and does not mention Coventry at all in the text though she discusses cover stories for Ultra.

Another sign that this book was written by a novice is the continual use of German words instead of translating them into English: aside from continually referring to all the German military organizations as Heer, Marine, Wehrmacht, and Luftwaffe, she refers to Auswärtiges Amt, Nachrichten Offizier, Stecker, Stichwortbefehl, entschlüsseln, schabbern, Rückmarsch, and a host of other words that could have been translated into English without further explanation. Usually a foreign word is included in a book if it loses its meaning in translation. In addition, several German names or words are misspelled (like Züse instead of Zuse). A good copy editor could have repaired details like this.

Despite these shortcomings, this is a valuable addition to the literature and addresses a very important question in understanding why the Germans lost the intelligence war. The final puzzle remains though: how did the 10,000 men and women who worked at Bletchley Park keep the secret for twenty-nine years, especially since they were centralized and shared information?!