Bomber stream

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A map of part of the Kammhuber Line showing the 'belt' and nightfighter 'boxes' through which the bomber stream flew

The bomber stream was a tactic developed by the Royal Air Force (RAF) Bomber Command to overwhelm the German aerial defences of the Kammhuber Line during World War II.

The Kammhuber Line consisted of three layers of zones about 32 km long (north-south) and 20 km wide (east-west).^{[citation needed]} In each zone there were two ground-directed night fighters known as "Tame Boar" (Zahme Sau). Initially RAF Bomber Command sent in their planes one at a time in order to force the defences to be spread as far apart as possible, meaning that any one aircraft would have to deal with little concentrated flak. However this also meant the Himmelbett centres in each cell were only dealing with perhaps one or two planes at a time, making their job much easier.

British analysis of the loss of bombers to night fighters of the Kammhuber Line was one of the first applications of statistical science which would become known as Operational Research. The introduction of GEE allowed the RAF bombers to fly by a common route and at the same speed to and from the target, each aircraft being allotted a height band and a time slot in a bomber stream to minimize the risk of collision. 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 any one Himmelbett zone.^{[citation needed]} It was then a matter of calculating the statistical loss from collisions against the statistical loss from night fighters to calculate how close the bombers should fly to minimise RAF losses. At the urging of R.V. Jones, Bomber Command reorganized their attacks into streams carefully positioned the stream to fly right down the middle of a cell. The first use of the bomber stream was the first 1,000 bomber raid against Cologne on the night of 30/31 May 1942.