 Air Chief Marshal Sir Arthur Harris, as Air Officer Commanding-in-Chief RAF Bomber Command, was in the midst of the Battle of the Ruhr, a campaign against the industrial conurbations of north-west Germany carried out from March to July 1943.These attacks, on targets only ninety minutes' flying time from Bomber Command bases, made use of the short spring and summer nights and also exploited the Oboe (navigation) radar-ranging device, which enabled high-flying Mosquito bombers of No.8 Group (Pathfinder Force) to place their pyrotechnic Target indicator (TI) bombs accurately.Reliant on signals from ground stations, Oboe was restricted by the curvature of the Earth to a range of from England.