Knickebein was the first system developed by the Germans for precision bomb attacks in England at night or in poor visibility.
A radio wave of about 30 MHz was sent directly against the target, and the bombers could hear from their radio in the cockpit when they were on the right track. A radio wave that crossed the first one, made it possible to determine the distance to the target. At 250 km. distance, a target could be hit with an accuracy of +/- 1500 meters.
In June 1940, the Englishmen picked up a signal that passed the Rolls-Royce factories in Derby. The subsequent bomb attack at the factory revealed the system for the English and, as a response, the English radio stations began to jam the German signal, later that year, thus preventing the Germans from precision. The German countermeasures meant, for example, that the signal was first activated when the bomb machines were close to the target or that one or more wrong targets were identified.
In parallel, the Germans were embarking on a more precise system, which was also more difficult to jam at the same time. This system was called X-Gerät.
The remains of the Knickebein radar installation are very easily recognizable today because of the round ring on which the antenna could be set.
A total of 13 stations were built throughout Europe, and only the one in Sicily never came to use:
Klepp - Norway - 22 km south-southwest of Stavanger
Stollberg - Germany - 3 km north-west of Bredstedt
Julianadorp - Holland - southwest of Den Helder
Kleve-Materborn - Germany - 58 km northwest of Duisburg
Bergen op Zoom - Holland - 50 km southwest of Rotterdam
Mont Violet - France - 13 km southeast of Boulogne
Greny - France - 16 km northeast of Dieppe
Mont Pinçon north Le Plessis-Grimoult - France - 30 km southwest of Caen
Beaumont - France - 16 km northwest of Cherbourg
Sortosville-en-Beaumont - France - 25 km southwest of Cherbourg
Saint-Fiacre at Plestin-les-Greves - France - 17 km northeast of Morlaix
Maulburg - Germany - 8 km northeast Lörrach
Noto - Italy - 27 km southwest of Syracuse (not completed)