Operation Corona

This was a deception practiced by the RAF (British air force) in WW2. Their Y Service closely monitored radio transmissions from the Luftwaffe and were quite familiar with the Germans' operations. In late 1943 the British began Operation Corona, which was, according to accounts, both successful and highly amusing for the British monitors.

The trick was simple: German Jews who had escaped to Britain were recruited and trained for the job because they spoke German perfectly. They began their radio career impersonating Luftwaffe ground controllers and giving pilots phoney instructions with the intent of causing confusing and disrupting operations. German pilots were instructed to land immediately, head off for another patrol area, or follow a course which led them completely astray. The contest of real controller versus fake and the resulting confusion got so bad that the Luftwaffe switched to using women for controllers, hoping the change in voices would help. The RAF hoaxers promptly switched to German-speaking WAAF members and continued harassing the Luftwaffe.

This operation ran from October 1943 to May 1945 (war ended). The report of it is in the British National Archives. It is also mentioned by Aileen Clayton in her book "The Enemy is Listening." Clayton was a member of the Y service at the time.