Double Cross System
Encyclopedia
The Double Cross System, or XX System, was a World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 anti-espionage and deception operation of the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 military intelligence arm, MI5
MI5
The Security Service, commonly known as MI5 , is the United Kingdom's internal counter-intelligence and security agency and is part of its core intelligence machinery alongside the Secret Intelligence Service focused on foreign threats, Government Communications Headquarters and the Defence...

. Nazi
Nazism
Nazism, the common short form name of National Socialism was the ideology and practice of the Nazi Party and of Nazi Germany...

 agents in Britain - real and false - were captured, turned themselves in or simply announced themselves and were then used by the British to broadcast mainly disinformation
Disinformation
Disinformation is intentionally false or inaccurate information that is spread deliberately. For this reason, it is synonymous with and sometimes called black propaganda. It is an act of deception and false statements to convince someone of untruth...

 to their Nazi controllers. Its operations were overseen by the Twenty Committee under the chairmanship of John Cecil Masterman
John Cecil Masterman
Sir John Cecil Masterman was a noted academic, sportsman and author. However, he was best known as chairman of the Twenty Committee, which during World War II ran the Double Cross System, the scheme that controlled double agents in Britain.-Academic background:Masterman was educated at the Royal...

; the name of the committee comes from the number 20 in Roman numerals: "XX".

The policy of MI5 during the war was initially to use the system for counter-espionage
Counter-Espionage
-Cast:* Warren William as Michael Lanyard* Eric Blore as Jamison* Hillary Brooke as Pamela Hart* Thurston Hall as Insp. Crane* Fred Kelsey as Detective Wesley Dickens* Forrest Tucker as Anton Schugg* Matthew Boulton as Inspector J...

. It was only later that its potential for deception purposes was realised. Agents from both of the German intelligence services, the Abwehr
Abwehr
The Abwehr was a German military intelligence organisation from 1921 to 1944. The term Abwehr was used as a concession to Allied demands that Germany's post-World War I intelligence activities be for "defensive" purposes only...

 and Sicherheitsdienst
Sicherheitsdienst
Sicherheitsdienst , full title Sicherheitsdienst des Reichsführers-SS, or SD, was the intelligence agency of the SS and the Nazi Party in Nazi Germany. The organization was the first Nazi Party intelligence organization to be established and was often considered a "sister organization" with the...

 (SD), were apprehended. Many of the agents who reached British shores turned themselves in to the authorities. Still others were apprehended when they made elementary mistakes during their operations. And some were false agents who had tricked the Germans into believing they would spy for them if they helped them reach England (e.g. Treasure
Nathalie Sergueiew
Nathalie Sergueiew was a female double agent working for MI5 during World War II under the codename TREASURE. She played a significant part in deceiving the Germans about the location of the D-Day landings....

, Fido
Roger Grosjean
Roger Grosjean started his career as a French Air Force fighter pilot in France, England and North Africa. This involved a short stint as a Security Service double agent during World War II . He then became a very successful archeologist in Corsica. Grosjean was born on July 25, 1920, in...

). Later agents were instructed to contact agents in place who, unknown to the Abwehr, were already controlled by the British. The Abwehr and SD sent agents over by a number of means including parachute drops, submarine and travel via neutral countries. The last route was most commonly used, with agents often impersonating refugees. After the war it was discovered that all the agents Germany sent to Britain had given themselves up or been captured, with the possible exception of one who committed suicide.

Methods of operation

The main form of communication that agents used with their handlers was secret writing. Letters were intercepted by the postal censorship authorities and some agents were caught by this method. Later in the war, wireless set
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

s were provided by the Germans. Eventually transmissions purporting to be from one double agent
Double agent
A double agent, commonly abbreviated referral of double secret agent, is a counterintelligence term used to designate an employee of a secret service or organization, whose primary aim is to spy on the target organization, but who in fact is a member of that same target organization oneself. They...

 were facilitated by transferring the operation of the set to the main headquarters of MI5 itself. On the British side, a critical aid in the fight against the Abwehr and SD was the breaking of the German ciphers
Code (cryptography)
In cryptography, a code is a method used to transform a message into an obscured form, preventing those who do not possess special information, or key, required to apply the transform from understanding what is actually transmitted. The usual method is to use a codebook with a list of common...

. Abwehr hand ciphers were cracked early in the war, and SD hand ciphers and Abwehr Enigma ciphers followed thereafter. The signals intelligence allowed an accurate assessment of whether the double agents were really trusted by the Germans and what effect their information had.

A crucial aspect of the system was the need for genuine information to be sent along with the deception material. This need caused problems on a regular basis early in the war, with those who controlled the release of information reluctant to provide even a small amount of relatively innocuous genuine material. Later in the war, as the system became a more coherent whole, genuine information was integrated into the deception system. For example, one of the agents sent genuine information about Operation Torch
Operation Torch
Operation Torch was the British-American invasion of French North Africa in World War II during the North African Campaign, started on 8 November 1942....

 to the Germans. It was postmarked before the landing, but due to delays deliberately introduced by the British authorities the information did not reach the Germans until after the Allied troops were ashore. The information impressed the Germans as it appeared to date from before the attack, but it was militarily useless to them.

Operation outside the United Kingdom

It was not only in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 that the system was operated. A number of agents connected with the system were run in Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

 and Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

. Some even had direct contact with the Germans in occupied Europe. One of the most famous of the agents who operated outside of the UK was Tricycle
Dušan Popov
Dušan "Duško" Popov OBE was a double agent working for MI6 during World War II under the cryptonym Tricycle.-Origins of Tricycle:...

. There was even a case where an agent started running deception operations independently from Portugal using little more than guidebooks, maps and a very vivid imagination to convince his Abwehr handlers that he was spying in the UK. This agent, Garbo
Juan Pujol (alias Garbo)
Joan Pujol Garcia , also known as Juan Pujol García , MBE , was a double agent during the Second World War who was known by the British codename Garbo and the German codename Arabel...

, created an entire network of phantom sub-agents and finally succeeded in convincing the British authorities that he could be useful. He and his phantom sub-agents were absorbed into the main Double Cross system, and he became so respected by the Abwehr
Abwehr
The Abwehr was a German military intelligence organisation from 1921 to 1944. The term Abwehr was used as a concession to Allied demands that Germany's post-World War I intelligence activities be for "defensive" purposes only...

 that they stopped landing agents in Britain after 1942. They thus became wholly dependent on the spurious information which was fed to them by Garbo's network and the other Double Cross agents.

Results

Masterman expressed the opinion that as a consequence of Double Cross's efficacy, by early 1941, "we [MI5] actively ran and controlled the German espionage
Espionage
Espionage or spying involves an individual obtaining information that is considered secret or confidential without the permission of the holder of the information. Espionage is inherently clandestine, lest the legitimate holder of the information change plans or take other countermeasures once it...

 system in this country [United Kingdom]." This was confirmed after the end of the war.

Operation Fortitude and D-Day landings

The British put their double agent network to work in support of Operation Fortitude
Operation Fortitude
Operation Fortitude was the codename for a World War II military deception employed by the Allied nations as part of an overall deception strategy during the build up to the 1944 Normandy Landings...

, a plan to deceive the Germans about the location of the invasion of France. Allowing one of the double agents to claim to have stolen documents describing the closely guarded invasion plans might have aroused suspicion. Instead, agents were allowed to report minutiae such as insignia on soldiers' uniforms and unit markings on vehicles. The observations in the south-central areas largely gave accurate information about the units located there: the actual invasion forces. Reports from southwest England indicated few troop sightings, when in reality many units were housed there. Reports from the southeast depicted the real and the notional Operation Quicksilver
Operation Quicksilver (WWII)
In World War II, Operation Quicksilver was a sub-plan of Operation Fortitude, the 1944 deception plan designed to induce the Germans to hold troops away from Normandy in belief that the Normandy landing was only a feint and that the major invasion would come in the Pas-de-Calais...

 forces. Any military planner would know that to mount a massive invasion of Europe from England, Allied
Allies of World War II
The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

 units had to be staged around the country, with those that would land first nearest to the invasion point. German intelligence used the agent reports to construct an order of battle
Order of battle
In modern use, the order of battle is the identification, command structure, strength, and disposition of personnel, equipment, and units of an armed force participating in field operations. Various abbreviations are in use, including OOB, O/B, or OB, while ORBAT remains the most common in the...

 for the Allied forces that placed the centre of gravity of the invasion force opposite Pas de Calais, the point on the French coast closest to England and therefore a likely invasion site. The deception was so effective that the Germans kept 15 reserve divisions near Calais even after the invasion had begun at Normandy, lest it prove to be a diversion from the main invasion at Calais.

The Allies were willing to risk exposing the Double Cross network to achieve the needed surprise for the Normandy invasion. However, early battle reports of insignia on Allied units that the German armies encountered only confirmed the information the double agents had sent, increasing the Germans' trust in their network. Some of the double agents were informed in radio messages from Germany after the invasion that they had been awarded the Iron Cross
Iron Cross
The Iron Cross is a cross symbol typically in black with a white or silver outline that originated after 1219 when the Kingdom of Jerusalem granted the Teutonic Order the right to combine the Teutonic Black Cross placed above a silver Cross of Jerusalem....

.

V-weapons deception

The British noticed that, during the V-1 flying bomb
V-1 flying bomb
The V-1 flying bomb, also known as the Buzz Bomb or Doodlebug, was an early pulse-jet-powered predecessor of the cruise missile....

 attacks of 1944, the weapons were falling 2–3 miles short of Trafalgar Square
Trafalgar Square
Trafalgar Square is a public space and tourist attraction in central London, England, United Kingdom. At its centre is Nelson's Column, which is guarded by four lion statues at its base. There are a number of statues and sculptures in the square, with one plinth displaying changing pieces of...

 (the actual Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....

 aiming points such as Tower Bridge
Tower Bridge
Tower Bridge is a combined bascule and suspension bridge in London, England, over the River Thames. It is close to the Tower of London, from which it takes its name...

 were unknown to the British). Duncan Sandys
Duncan Sandys
Edwin Duncan Sandys, Baron Duncan-Sandys CH PC was a British politician and a minister in successive Conservative governments in the 1950s and 1960s...

 was told to get MI5
MI5
The Security Service, commonly known as MI5 , is the United Kingdom's internal counter-intelligence and security agency and is part of its core intelligence machinery alongside the Secret Intelligence Service focused on foreign threats, Government Communications Headquarters and the Defence...

-controlled German agents such as Zig Zag
Eddie Chapman
Edward Arnold "Eddie" Chapman was an English pre-war criminal and wartime spy. During the Second World War he offered his services to Nazi Germany as a spy and a traitor whilst intending all along to become a British double agent. His British Secret Service handlers code named him 'ZIGZAG' in...

 and TATE
Wulf Schmidt
Wulf Dietrich Christian Schmidt, later known as Harry Williamson was Danish citizen who during World War II became a double agent working for Britain against Nazi Germany under the codename TATE....

 to report the V-1 impacts back to Germany. In order to make the Germans aim short, the British used the double agent
Double agent
A double agent, commonly abbreviated referral of double secret agent, is a counterintelligence term used to designate an employee of a secret service or organization, whose primary aim is to spy on the target organization, but who in fact is a member of that same target organization oneself. They...

s to exaggerate the number of V-1s falling in the north and west of London and not to report, when possible, those in the south and east. For example, circa June 22, 1944, only one of seven impacts was reported as being south of the Thames when ¾ of the impacts had been there. Although Germany was able to plot a sample of V-1s which had radio transmitters, which confirmed that they had fallen short, the telemetry was disregarded in favour of the human intelligence
HUMINT
HUMINT, a syllabic abbreviation of the words HUMan INTelligence, refers to intelligence gathering by means of interpersonal contact, as opposed to the more technical intelligence gathering disciplines such as SIGINT, IMINT and MASINT...

.

When the German 65th Army Corps received a false Double Cross V-1 report that there was considerable damage in Southampton —which had not been a V-1 target—the V-1s were temporarily aimed at the South Coast Ports. V1s were extremely powerful. As a result, the Double Cross deception also caused retargetting from London, not just inaccurate aiming. However, when V-1s launched from Heinkel He 111
Heinkel He 111
The Heinkel He 111 was a German aircraft designed by Siegfried and Walter Günter in the early 1930s in violation of the Treaty of Versailles. Often described as a "Wolf in sheep's clothing", it masqueraded as a transport aircraft, but its purpose was to provide the Luftwaffe with a fast medium...

s at Southampton on July 7 were inaccurate, British advisor Frederick Lindemann
Frederick Lindemann, 1st Viscount Cherwell
Frederick Alexander Lindemann, 1st Viscount Cherwell FRS PC CH was an English physicist who was an influential scientific adviser to the British government, particularly Winston Churchill...

 recommended the agents report that the attack caused "heavy losses" in order to save hundreds of Londoners each week at the expense of only a few lives in the ports. When the Cabinet learned on August 15 of the deception, Herbert Morrison
Herbert Morrison
Herbert Stanley Morrison, Baron Morrison of Lambeth, CH, PC was a British Labour politician; he held a various number of senior positions in the Cabinet, including Home Secretary, Foreign Secretary and Deputy Prime Minister.-Early life:Morrison was the son of a police constable and was born in...

 said that they had no right to decide that one man should die while another should survive, but the deception was approved to continue.

Moreover, when the subsequent V-2 rocket
V-2 rocket
The V-2 rocket , technical name Aggregat-4 , was a ballistic missile that was developed at the beginning of the Second World War in Germany, specifically targeted at London and later Antwerp. The liquid-propellant rocket was the world's first long-range combat-ballistic missile and first known...

 blitz
The Blitz
The Blitz was the sustained strategic bombing of Britain by Nazi Germany between 7 September 1940 and 10 May 1941, during the Second World War. The city of London was bombed by the Luftwaffe for 76 consecutive nights and many towns and cities across the country followed...

 began with only a few minutes from launch to impact, the deception was enhanced by providing locations genuinely damaged by bombing, verifiable by aerial reconnaissance, for impacts in central London, but each time-tagged with the time of an earlier impact that had fallen 5–8 miles short of central London. From mid-January to mid-February 1945, the mean point of V-2 impacts edged eastward at the rate of a couple of miles a week, with more and more V-2s falling short of central London.

List of Double Cross agents

  • Johnny Jebsen - "Artist"
  • Dickie Metcalf - "Balloon"
  • Joseph Lenihan - "Basket"
  • Beetle
  • Sam McCarthy - "Biscuit"
  • Elvira Chaudoir - "Bronx"
  • Roman Czerniawski
    Roman Czerniawski
    Roman Garby-Czerniawski was a Polish Air Force Captain and Allied double agent during World War II, using the codename Brutus.-Life:...

     - "Brutus"
  • Careless
  • Carrot
  • Charlie
  • Walter Dicketts - "Celery"
  • Hans George - "Dragonfly"
  • Henri Arents "Father"
  • Roger Grosjean
    Roger Grosjean
    Roger Grosjean started his career as a French Air Force fighter pilot in France, England and North Africa. This involved a short stint as a Security Service double agent during World War II . He then became a very successful archeologist in Corsica. Grosjean was born on July 25, 1920, in...

     - "Fido"
  • Freak
  • Hans Reysen - "Gander"
  • Juan Pujol - "Garbo"
  • Gerda Sullivan - "Gelatine"
  • Georges Graf - "Giraffe"
  • Gwilym Williams - "GW"
  • Albert de Jaeger - "Hatchet"
  • Josef
  • Lipstick
  • Meteor
  • Mullett
  • Helge Moe and Tor Glad - Mutt and Jeff
    Mutt and Jeff (spies)
    Mutt and Jeff were spies who worked for the United Kingdom and MI5 and were members of the Double Cross System.In April 1941 two Norwegians, Helge Moe and Tor Glad fetched up on a remote Aberdeenshire beach, having travelled by seaplane and rubber dinghy...

  • José Brugada - "Peppermint"
  • Puppet
  • Günther Schütz
    Günther Schütz
    Günther Schütz was a German citizen who performed a mission for German Intelligence in World War II, as part of Britain's Double Cross System.-Early life:Schütz was born on 17 April 1912 in the Silesian town of Schweidnitz...

     - "Rainbow"
  • Rover
  • Shepherd
  • Snarck, The
  • Sniper
  • Arthur Owens
    Arthur Owens
    Arthur Graham Owens, later known as Arthur Graham White was a Welsh electrical engineer who acted as a mole during World War II. He was working for MI5 while appearing to the Abwehr to be one of their agents. Owens was known to MI5 by the codename SNOW...

     - "Snow"
  • Hans von Kotze - "Springbok"
  • Gösta Caroli
    Gösta Caroli
    Gösta Caroli was a double agent working for MI5 during World War II under the codename SUMMER.- Further reading :...

     - "Summer"
  • William Jackson
    William Jackson
    -In politics:*William Jackson , US Congressman from Massachusetts*William Jackson , Secretary to the Philadelphia Convention and member of the U.S. Continental Army...

     - "Sweet William"
  • Wulf Schmidt
    Wulf Schmidt
    Wulf Dietrich Christian Schmidt, later known as Harry Williamson was Danish citizen who during World War II became a double agent working for Britain against Nazi Germany under the codename TATE....

     - "Tate"
  • Teapot
  • Nathalie Sergueiew
    Nathalie Sergueiew
    Nathalie Sergueiew was a female double agent working for MI5 during World War II under the codename TREASURE. She played a significant part in deceiving the Germans about the location of the D-Day landings....

     - "Treasure"
  • Dušan Popov
    Dušan Popov
    Dušan "Duško" Popov OBE was a double agent working for MI6 during World War II under the cryptonym Tricycle.-Origins of Tricycle:...

     - "Tricycle"
  • Washout
  • Werner von Janowski - "Watchdog"
  • Weasel
  • Worm, The
  • Eddie Chapman
    Eddie Chapman
    Edward Arnold "Eddie" Chapman was an English pre-war criminal and wartime spy. During the Second World War he offered his services to Nazi Germany as a spy and a traitor whilst intending all along to become a British double agent. His British Secret Service handlers code named him 'ZIGZAG' in...

    - "Zig Zag"
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