WORLD WAR II FROM A TO Z
The XX System or Double-Cross System was a World War II anti-espionage and deception operation of the British Security Service, a civilian organization usually referred to by its cover title 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 realized. 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.
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 center 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.
The following video is 1 of 5 parts of Timewatch The Spies that Fooled Hitler World War II. I have only embedded the first but all are available on YouTube.