This was an Allied radio deception plan during and after the launch of 'Overlord' (6 June/6 July 1944).
One of the few elements of the original 'Appendix Y' plan to reach the stage of implementation was the observance of several periods of total radio silence during the pre-invasion period, the Allies believing that this would be interpreted by the Germans as a 'crying wolf' attempt to persuade them not to read radio silence during the assault loading period as an indication that the invasion of North-West Europe was actually starting.
The undertaking was in some respects a double bluff, for this radio silence was actually continue uninterrupted during the loading period. In 'Williams', for example, a US radio deception unit was inserted into the radio net of Lieutenant General Omar N. Bradley’s US 1st Army and continued to simulation that formation after this army had gone 'radio silent' for the invasion, and in 'Quaker' the British undertook a similar effort. Then from H-Hour of D-Day until 6 July, radio silence was imposed on every non-operational net in the UK in 'Adoration'.