Double-Cross System

The Double-Cross System, or XX System, was a World War II anti-espionage and deception operation of the British military intelligence arm, MI5. Nazi 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 to their Nazi controllers. Its operations were overseen by the Twenty Committee under the chairmanship of John Cecil Masterman; the name of the committee comes from the number 20 in Roman numerals: "XX" (i.e. double crosses).

The policy of MI5 during the war was initially to use the system for counter-espionage. It was only later that its potential for deception purposes was realised. Agents from both of the German intelligence services, the Abwehr and Sicherheitsdienst (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. In addition, 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, Fido). 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 had been captured with the possible exception of one who committed suicide.

Early agents
Following a July 1940 conference in Kiel, the Abwehr (German intelligence) launched an espionage campaign against Britain involving both intelligence gathering and sabotage. The spies were sent over from Europe in various ways; some parachuted or came off a submarine. Others entered the country on false passports, or posing as refugees.

Public perception in Britain at that time was that the country was full of well trained German spies who were deeply integrated into society. There was widespread, as Churchill put it, "spy-mania". The truth was that between September and November 1940 fewer than twenty five agents arrived in the country; mostly of Eastern European extraction, badly trained and poorly motivated.

The agents were not difficult to spot - a task made still easier by the cracking of the German's Enigma encryption. MI5, with advance warning of infiltration, had no trouble picking up almost all of the spies sent to the country. Writing in 1972, John C. Masterman (who would later head the Twenty Committee) said that by 1941 MI5 "actively ran and controlled the German espionage system in [the United Kingdom]." It was not an idle boast; post-war records confirmed that none of the Abwehr agents, bar one that committed suicide, went unnoticed.

Once caught, the spies were deposited in the care of Captain Robert Stephens at Camp 020 (Latchmere House, Richmond). After Stephens, a notorious and brilliant interrogator, had picked apart their life history, the agents were either spirited away (to be imprisoned or executed) or, if judged acceptable, offered the chance to turn double on the Germans.

Control of these new double agents fell to Thomas Argyll Robertson (usually called Tar, from his initials), a charismatic MI5 agent. A Scot, and something of a playboy, Robertson had some early experience with double agents; just prior to the war he had been case officer to Arthur Owens (code name Snow). Owens was an oddity, and it became apparent that he was simply playing the Germans and British against each other – to what end Robertson was unable to uncover. The experiment had not appeared to be a success, but MI5 had learned key lessons about how the Abwehr operated and how double agents might be useful.

Robertson, in particular, believed that turning German spies against their masters would have numerous benefits; for example determining what information the Abwehr wanted or to actively mislead them as part of a military deception. In addition, it would discourage them from sending more agents if they believed an operational network existed. Section B1A (a subordinate of B section, under Guy Liddell) was formed and Robertson was put in charge of handling the double-agent program.

Robertson's first agents were not a success; Giraffe (George Graf) was never really used and Gander (Kurt Goose; MI5 had a thing for amusingly relevant code names) had been sent to Britain with a radio that could only transmit, not receive. Both were quickly decommissioned. The next two attempts involved even more farce; Gösta Caroli and Wulf Schmidt (a Danish citizen) landed, via parachute, in September 1940. The two were genuine Nazis, had trained together and were friends. Caroli was coerced into turning double in return for Schmidt's life being spared, whilst Schmidt was told that Caroli had sold him out and in anger swapped sides.

Caroli quickly became a problem; he attempted to strangle his MI5 handler before making an escape carrying a canoe, on a motorcycle. He vaguely planned to row to Holland, but came unstuck after falling off the bike in front of a policeman. He was eventually recaptured and judged too much trouble to be used. Schmidt was more of a success. Codenamed 'Tate', he continued to contact Germany until May 1945. However, these eccentric spies made Robertson aware that handling double agents was going to be a difficult task.

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 sets were provided by the Germans. Eventually transmissions purporting to be from one double agent 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. 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 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 that the system was operated. A number of agents connected with the system were run in neutral Spain and Portugal. 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 Dusan Popov ("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, Juan Pujol ("Garbo"), created an entire network of phantom sub-agents and finally succeeded in convincing the British authorities that he could be useful. He and his fictitious network were absorbed into the main Double-Cross System, and he became so respected by the Abwehr 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.

Operation Fortitude and D-Day landings
The British put their double-agent network to work in support of Operation Fortitude, 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 forces. Any military planner would know that to mount a massive invasion of Europe from England, Allied 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 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.

V-weapons deception
The British noticed that, during the V-1 flying bomb attacks of 1944, the weapons were falling 2–3 miles short of Trafalgar Square — the actual Luftwaffe aiming points such as Tower Bridge were unknown to the British. Duncan Sandys was told to get MI5-controlled German agents such as Zig Zag and TATE to report the V-1 impacts back to Germany. In order to make the Germans aim short, the British used the double agents 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.

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. V-1s 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 111s at Southampton on July 7 were inaccurate, British advisor Frederick Lindemann 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 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 blitz 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

 * "Artist" – Johnny Jebsen
 * "Balloon" - Dickie Metcalf
 * "Basket" - Joseph Lenihan
 * "Beetle"
 * "Biscuit" - Sam McCarthy
 * "Bronx" - Elvira Chaudoir
 * "Brutus" - Roman Czerniawski
 * "Careless"
 * "Carrot"
 * "Charlie"
 * "Celery" - Walter Dicketts
 * "Dragonfly" - Hans George
 * "Father" - Henri Arents
 * "Fido" - Roger Grosjean
 * "Freak" - Marquis Frano de Bona
 * "Gander" - Hans Reysen
 * "Garbo" - Juan Pujol
 * "Gelatine" - Gerda Sullivan
 * "Giraffe" - Georges Graf
 * "GW" - Gwilym Williams
 * "Hatchet" - Albert de Jaeger
 * "Le Chat" - Mathilde Carré
 * "Lipstick"
 * "Meteor"
 * "Mullett"
 * "Mutt and Jeff" - Helge Moe and Tor Glad, two Norwegians
 * "Peppermint" - José Brugada
 * "Puppet"
 * "Rainbow" - Günther Schütz
 * "Rover"
 * "Shepherd"
 * "The Snark" - Maritza Mihailovic, a Yugoslavian
 * "Sniper"
 * "Snow" - Arthur Owens
 * "Springbok" - Hans von Kotze
 * "Summer" - Gösta Caroli
 * "Sweet William" - William Jackson
 * "Tate" - Wulf Schmidt
 * "Teapot"
 * "Treasure" - Nathalie Sergueiew (Lily Sergeyev)
 * "Tricycle" - Dušan Popov
 * "Washout"
 * "Watchdog" - Werner von Janowski
 * "Weasel"
 * "The Worm"
 * "Zigzag" - Eddie Chapman


 * Charles Cholmondeley