Another tactic that proved effective was to send their own planes to England while the raids were taking off or landing. Radio operators listening to the RAF bomber frequencies were able to recognize the start of a raid and the raiding force of about 30 night fighters would be sent over the RAF airbases to shoot down the bombers as they took off or landed. By the beginning of October the night intruder force had claimed a hundred kills but on October 13, Hitler ordered the force sent to the Mediterranean, despite their success.