page_title: Dowding system
section_title: Aftermath
hierarchical_section_title: Dowding system / Aftermath
caption_attribution_description: English: GCI (Ground Control of Interception) radar installation at RAF Sopley, Hampshire, 1945. Ground Control of Interception: AMES Final Type 7 GCI Fixed radar installation at RAF Sopley, Hampshire. The Type 7 was a metric radar operating in the 1.5 metre wave band, the usual operating frequency being 209 MHz. The aerial system in the foreground is mounted over the Radar Well, which houses the transmitter and receiver, and is connected to the Operations Building (known as the "Happidrome") in the right distance.
context_page_description: The Dowding system was the world's first wide-area ground-controlled interception network, controlling the airspace across the United Kingdom from northern Scotland to the southern coast of England. It used a widespread dedicated land-line telephone network to rapidly collect information from Chain Home radar stations and the Royal Observer Corps in order to build a single image of the entire UK airspace and then direct defensive interceptor aircraft and anti-aircraft artillery against enemy targets. The system was built by the Royal Air Force just before the start of World War II, and proved decisive in the Battle of Britain.
  The Dowding system was developed after tests demonstrated problems relaying information to the fighters before it was out of date. Air Chief Marshal Hugh Dowding, commander of RAF Fighter Command, solved the problem through the use of hierarchical reporting chains. Information was sent to Fighter Command Headquarters central filter room at Bentley Priory and used to prepare a map of the battle. Details of the map were then relayed to the Group and Sector headquarters, where operators re-created the map at a scale covering their area of operations.
context_section_description: Dowding resisted suggestions to devolve the filter room to the group level to reduce demand on FCHQ. The matter was raised several times, the last time on 27 September, when the Air Council's request was once again dismissed by Dowding. He was then summoned to the Air Staff on 1 October and was forced to implement this change, although he delayed this until all fighters were equipped with new IFF Mark II systems.
  On 24 November 1940, Dowding was removed from command. This was due partly to his lack of action on ending the feud between Leigh-Malory and Park, partly due to his refusal to devolve command, and partly due to the lack of success against the increasing tempo of night bombing, which by this time had become The Blitz.
  The groups soon had their own filter rooms. The introduction of ground-controlled interception radars (GCI) in the winter of 1940–41 allowed further devolution of command because sector controllers could directly detect and control the aircraft in their area. Working with IFF, now widely used, the GCI display eliminated the need for separate detection and plotting, as well as the communications links and manpower needed to operate the reporting system. The Dowding system remained in use for the rest of the war for daytime missions, both for (rare) defensive situations, as well providing support for aircraft supporting offensive daytime raids during 1943 and later.
  After the war, the fighter control system was largely demobilized. The explosion of the Soviet atomic bomb in 1949 and the presence of Tupolev Tu-4 "Bull" aircraft that could deliver it to the UK led to the rapid construction of the ROTOR system. ROTOR re-used many existing GCI and CH systems with more sophisticated control rooms in fortified underground bunkers. ROTOR was itself replaced by AMES Type 80 Master Control rooms and then the Linesman/Mediator system in the 1960s.
caption: GCI radars allowed a station to provide detection, identification (IFF) and fighter direction, eliminating the need for the complex reporting chains of the Dowding system.
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