" Fortunately, the British security service had captured all German agents in Britain. Most of them had been ‘turned’ to send back misleading information to their controllers. This ‘Double Cross’ system, supervised by the XX Committee, was designed to produce a great deal of confusing ‘noise’ as a key part of Plan Fortitude. Fortitude was the most ambitious deception in the history of warfare, a project even greater than the maskirovka then being prepared by the Red Army to conceal the true target of Operation Bagration, Stalin’s summer offensive to encircle and smash the Wehrmacht’s Army Group Centre in Belorussia. Plan "

― Antony Beevor , D-Day: The Battle for Normandy