Kammhuber Line

RAF bombers flying into Germany or France had to cross the line at some point, at which time the Freya radar operators directed the master searchlight to illuminate the plane.

Once this had happened other manually controlled searchlights also picked up the plane, and the night fighters were directed to intercept the illuminated bomber.

To aid interception a number of the night fighters were fitted with a short-range infrared device known as the Spanner-Anlage but these proved almost useless.

British intelligence soon discovered the nature of the Kammhuber Line and started studying ways to defeat it.

The boxes of the Kammhuber Line were well set up to deal with the broad approach paths of individual bombers.

Data provided to the British scientists allowed them to calculate that the bomber stream would overwhelm the six potential interceptions per hour that the German night fighters could manage in a Himmelbett zone.

Although the success rate of the line dropped, the network of radars and plotting stations continued to prove their worth.

Now when a raid started, night fighters from any base within range were directed into the stream, where it was hoped they would be able to find aircraft with their radar.

At the same time a massive building program started to add hundreds of Würzburgs to the system, although the infrastructure needed was extensive.

The German radar operators eventually learned to spot the lead bombers at the edge of the windowing, making it less effective.

The British also attacked the communications between ground stations and fighters, with Operation Corona, broadcasting false directions in authentic accents over the radio.