The Luftwaffe had navigational transmitters (Knickerbein or crooked leg) located in the Cherbourg Peninsula and Holland which provided navigation signals to most cities in England although the raids on Belfast were helped by navigational assistance in the form of city lighting from the neutral Irish Free State.
In the wake of the Butt Report, navigation was given the highest priority hence the development of radio aids such as Oboe which was accurate enough to be used against individual targets at night such as the raid in 1943 which destroyed much of the Krupp armaments factory in Essen, however Oboe was limited by the curvature of the earth and that is why the Oboe receivers were installed in the higher flying DH Mosquitoes which were armed with flares to mark the aiming point. Oboe had this limitation until summer 1944 when the Western Allies liberated France, Belgium, and Holland and then the Oboe transmitters could provide greater coverage to the East by being situated in those liberated countries.
In my opinion one further thing which is not appreciated by armchair critics of the Bomber campaign in the safety and security of the 21st Century is that the First World War had only been over 20 years before the start of the Second World War.
Most of the RAF Senior Officers, including Harris and Prime Minister Churchill himself had served in the trenches during that murderous conflict and who can blame them for trying new ways of fighting a war and avoiding the horrors and carnage that they had seen in the mud and blood of Flanders and France during the First World War.
Last edited by DC10RealMan; 20th Feb 2013 at 18:10.