Letter: Oboe notes

Sir: Michael Cumming's interesting article laments that the Oboe blind- bombing system did not receive more widespread use (Historical Notes, 1 December). There were two simple reasons.

First, the beam could only be picked up in a straight line from the transmitter: as the Earth curved away the minimum height above ground at which it could be received increased, the further the aircraft was from the transmitter. The aircraft ceiling of the time was around 30,000 feet, which gave a maximum range of 300 miles. The furthest target possible was the Ruhr. The majority of German cities were beyond its range.

Second, only one aircraft at a time could use the system. Bomber Command had earlier realised that single aircraft over a target were easy prey to defences and developed the stream tactic. This placed up to 1,000 bombers over a target in a little over an hour, overwhelming the defences and reducing casualty rates.

Consequently it was decided to use Oboe solely as a means of accurate marking. Other devices, such as the H2S ground-mapping radar, were developed to extend the range of bomber operations. However, they were not as accurate as Oboe and area bombing remained the only option at night.