Double-Cross System

Title:                  Double-Cross System

Author:                J. C. Masterman

Masterson, J. C. (2012). The Double-Cross System: The Incredible True Story of How Nazi Spies Were Turned into Double Agents. Guilford, DE: The Lyons Press

LCCN:    2011024581

D810.S7 M28 2012

Originally published

·         (1972). The Double-Cross System in The War of 1939 To 1945. New Haven, CT: Yale University Press

LCCN:    77158140

D810.S7 M28 1972


Date Updated:  March 8, 2017

The Double-Cross System has gone through a number of revisions since 1979, and includes an introduction by Nigel West. It is the amazing true story of how British intelligence penetrated and practically operated Nazi German’s spy network within the British Isles. With great imagination, care and precise coordination, the British were able to identify Nazi agents, induce many to defect, and supply Germany completely false information about bombings, battles, and even the D-Day invasion. Told by the man who himself masterminded the entire unbelievable four-and-a-half-year scheme, and filled with dazzling tidbits and extraordinary stories, The Double-Cross System is a testimony to Britain’s skill in the fine art of counterespionage.

The book was written right at the end of the European campaign of WWII while the author was still on active duty with the British Government. The text was initially an official memorandum of the Double-Cross (XX) System which was declassified and published around 1970. This is a different version of the first book on Double-Cross. XX was apparently successful in identifying all German agents operating in Britain and either turning them into double agents serving British interests or eliminating them.

Each of the agents was given a British code name. SUMMER, for example was launched on September 6, 1940, with order to report on air raid damage in Birmingham. As far as the Germans knew, he took up broadcasting after an illness and after contacting other German agents in Britain. In fact, SUMMER first attempted suicide, then tried to make his escape from England by a small boat. Although he was caught and imprisoned, it was a close call, for if he had returned to Germany and reported, it would have ruined the whole operation. From his case, the British concluded that each turned agent had to be physically and psychologically watched very carefully.

SNOW was an agent who worked with the British from early in the war, as were TRICYCLE and GIRAFFE. These three were particularly useful in building the impression that Germany was successful creating a whole network of agents, as they sent back messages reporting contact with new arrivals as they were caught and turned.

In most cases, the actual agent would be used to collect and relay messages. However, in some cases, the turned agent would be provided with a list of notional sub-agents, sending a mix of disinformation and genuine data. A “notional agent,” or piece of information, is one that is entirely imaginary, created as a fiction, convincing to the enemy. The Double Cross system in Britain included not only turned double agents, but also some notional subagents and even notional networks.

Gradually the British came to realize that they effectively controlled the whole German human intelligence system in Britain. When new agents were captured, they revealed under questioning that they had been told to report to one of the most trusted agents already there, including TATE, SNOW, GIRAFFE, and others. The British also learned from Ultra decodes that the Germans trusted the spies in Britain, all of whom were either turned or had been replaced by British agents sending false reports.

Masterman cites seven specific reasons for running the XX System:

  1. To control the enemy system or as much as we could get our hands on
  2. To catch fresh spies when they appear
  3. To gain knowledge of the personalities and methodologies of the German Secret
  4. To obtain information on the code and cipher work of the German services
  5. To get information of enemy plans and intentions from the questions asked by
    them [questions assigned to German agents in Britain]
  6. To influence enemy plans by the answers went to the enemy [in response to their
  7. To deceive the enemy about our own plans and intentions.

Achieving any of these goals would have more than justified the efforts of the XX System. Incredibly, all of them were achieved to a great extent.

One of the more famous operations, Operation MINCEMEAT, was the basis for the movie The Man Who Never Was[1]. In this operation, a body dressed as a major in the Royal Marines was released by a British submarine so as to wash up on the coast of Spain in the knowledge that the neutral but fascist government would provide any information to the Germans. Chained to the body was a dispatch case containing apparently official letters indicating that the next allied move after North Africa would be an invasion of either Greece or Sardinia. This was deliberate disinformation intended to lead the Germans away from the actual plan of invading Sicily. The deception was entirely successful.

Masterman also provides details of several other successful deceptions associated with the Normandy Invasion and with leading the Germans to inaccurately target their V-1 and V-2 weapons.

The book is a good, concise summary of the XX System. For the reader interested in a broader and more detailed treatment of the subject, I’d also recommend Anthony Cave Brown’s Bodyguard of Lies[2].

There are many editions of this work, first published in 1972. It was written by one of the key players in the counterintelligence battle with the Germans. This classic book describes arguably one of the greatest intelligence deception operations in modern war. Importantly for practitioners, it lays out the theory and practice of double agentry and denial and deception operations. Masterman describes in detail how the British turned and controlled almost all the German agents in the U.K., and how MI5 controlled and deceived the Germans with national agent networks carefully passing a mixture of genuine information and disinformation. Many valuable counterintelligence insights and principles that apply today as they did then are included. Note in particular the imaginative lengths the British went to in preparing believable passage material and the carte with which they handled and coordinated their extensive stable of double agents. This is one of several books recommended by Dan Mulvenna, in his “The Intelligence Officer’s Bookshelf: An annotated bibliography,” compiled by Dan Mulvenna (updated December, 2011) referring to British Intelligence–from WWII to the Present.

Nigel West is a author and consultant on counterintelligence matters. I had the privilege of hearing a series of his lectures about the Queen Mary II in the summer of 2010. This book was one of the ten best books on the Spying Game.

Reviewed by George C. Constantinides[3]

Masterman was head of the XX or Double Cross Committee throughout the war as a member of Ml5. This report he completed shortly after the end of the war. Except for a few cuts and verbal changes, the author says, it is in its original form. Declassified on the insistence of the author, it is one of the great works of intelligence literature, an outstanding one in the area of deception, and perhaps the greatest work yet written on double agents. It is a textbook on the acquisition, handling, control, and exploitation of such agents. Never has their systematic employment been revealed by a government to such an extent and with so much frankness. Many details Masterman provides have become well known to students of intelligence and deception operations, and the lessons, theory, and practice he spells out had become inbedded in varying degrees in postwar thinking and operations even before the work appeared. This happened despite Masterman’s warnings that no fixed principles or invariable rules could be derived from this history and that in the future advantages comparable to those enjoyed against the Germans were unlikely to occur.

Principally dealt with is the deceptive use of double agents rather than their employment for counterespionage and positive intelligence. Masterman was reluctant to judge the XX Committee’s work in deception, but John Bevan, the controller of LCS, the deception body in London, went on record that the Germans were deceived largely by such agents. Dennis Wheatley, also in LCS, said in RUSI that only this book gave an entirely truthful account of the part played by MI5 in deception. The book, however, contains a few errors (although surprisingly few for a report so early after the events) and has one major omission. Masterman seems in error on the inspiration for Operation Mincemeat. His conclusions were premature on the probable success of certain deception plans and operations: Dakar in 1942, the 1943 invasion deception for Norway, the 1943 deception operations designed to make the Germans fear an invasion of Western Europe. The principal omission is of any mention of the crucial role of Ultra. Masterman can only make veiled references to “secret sources” that gave final confirmation of their control of the whole German network and that the agents were believed.

Major criticism of the work has come from Mure in Master of Deception[4]. Mure objects to what he considers the impression that deception rested solely on MI5 and its double agents, is critical of XX Committee’s handling of its double agents, and contests Masterman’s remark that Torch, the invasion of North Africa, was a triumph of security rather than of deception. Masterman clearly stated that “the home of successful deception was in the Middle East” where Mure served and which Mure felt was neglected by Masterman and others of the London-based group, as was the work of Dudley Clarke, Mure’s superior. Masterman’s book contains the first word of the Pearl Harbor questionnaire given to the agent Tricycle and whose significance was missed or not emphasized by U.S. and British intelligence. See also Montagu’s Beyond Top Secret Ultra[5] for the only other first-hand account of the XX Committee’s work. DIS’s Bibliography [see below] calls this a classic and a veritable treatise on counterintelligence and deception. Masterman’s reasons for his fight to publish this report are given in greater detail in his On the Chariot Wheel[6].

This is a review by the Defense Intelligence School.[7]

The late Sir John Masterman was Chairman of the British Double-Cross (XX) Committee during World War II. At the end of the war, he wrote this text as an official classified history. Release, slightly sanitized, was authorized for publication by the British authorities in 1971. The book describes the highly complex and successful efforts of British Intelligence to neutralize, and in many cases to utilize, the services of every German Britain during the War. A major text on counterintelligence and deception, the book is a veritable classic treatise on this type of work, and the meticulous coordination which it requires.

Reviewed by Paul W. Blackstock and Frank L. Schaf[8] (of the 1972 version)

Almost all German agents of any importance who penetrated Great Britain during World War II were captured, converted into double agents, and worked under the control of M.I.5, sending fictitious reports back to Germany and diverting German attention from Normandy to the Pas de Calais before the invasion of June 1944. The classified report on this operation was written in 1945 by Sir John Masterman, who has since become an Oxford historian, to ensure that the experience and expertise acquired would not be lost. The Official Secrets Act was waived to permit publication of the report as a book in 1971-72. In addition to a description and evaluation of the strategic deception involved, the author makes a number of pertinent observations on the care and handling of double agents, the necessity for planning and coordination, and the potential value of espionage and counterespionage in time of war. In a prepublication interview Masterman stated: “The Secret Service gets blackguarded all over the place. I have wanted this book published to improve what nowadays is called its image. Germany had no spies here during the war who were not under our control. The building up of these people was a matter of years. We started with counterespionage and went on to intelligence and from that to deception” (New York Times, 14 November 1971)[9].

Further review by Paul W. Blackstock and Frank L. Schaf[10]

Describes in detail the highly successful counterespionage and deception operations conducted by British counterintelligence in which they controlled most of the German agents in Great Britain during World War II. Through this control the British were able to plant false information (subsequently reported to Berlin) as to where the main thrust of the Allied invasion would take place. For another annotation, see chapter 15, section D1.

[1] See Montagu, Ewen (1953). The Man Who Never Was: World War II’s Boldest Counter-Intelligence Operation. London, Evans Bros, upon which the movie was loosely based.

[2] Cave Brown, Anthony (1976). Bodyguard of Lies. London: W. H. Allen

[3] George C. Constantinides in Intelligence and Espionage: An Analytical Bibliography. Boulder, CO: Westview Press (1983), pp. 321-323

[4] Mure, David (1980). Master of Deception: Tangled Webs In London And The Middle East. London: William Kimber

[5] Montagu, Ewen (1977, 1978). Beyond Top Secret Ultra. New York: Coward, McCann & Geoghegan

[6] Masterman, John C. (1975). On the Chariot Wheel: An Autobiography. New York: Oxford University Press

[7] Defense Intelligence School (1981). Bibliography of Intelligence Literature: A Critical And Annotated Bibliography of Open-Source Literature (7th ed, rev.). Washington, DC: Defense Intelligence School, p. 43

[8] Blackstock, Paul W. (1978) and Frank L. Schaf, Jr. Intelligence, Espionage, Counterespionage, And Covert Operations: A Guide to Information Sources. Detroit: Gale Research Co., p. 186

[9] Anthony Lewis, “Briton Wins the Right to Publish Tale of World War II Espionage,” The New York Times, (November 14, 1971).

[10] Blackstock, Paul W. (1978) and Frank L. Schaf, Jr. Intelligence, Espionage, Counterespionage, And Covert Operations: A Guide to Information Sources. Detroit: Gale Research Co., p.



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