Editing Ground-controlled interception (section)

{{Short description|System for intercepting hostile aircraft}}
'''Ground-controlled interception''' ('''GCI''') is an [[air defence]] tactic whereby one or more [[radar station]]s or other observational stations are linked to a command communications centre which guides [[interceptor aircraft]] to an airborne target. This tactic was pioneered during [[World War I]] by the [[London Air Defence Area]] organization, which became the [[Royal Air Force]]'s [[Dowding system]] in [[World War II]], the first national-scale system. The ''[[Luftwaffe]]'' introduced similar systems during the war, but most other combatants did not suffer the same threat of air attack and did not develop complex systems like these until the [[Cold War]] era.

Today the term GCI refers to the style of battle direction, but during WWII it also referred to the radars themselves. Specifically, the term was used to describe a new generation of radars that spun on their vertical axis in order to provide a complete 360 degree view of the sky around the station. Previous systems, notably [[Chain Home]] (CH), could only be directed along angles in front of the antennas, and were unable to direct traffic once it passed behind their shore-side locations. GCI radars began to replace CH starting in 1941/42, allowing a single station to control the entire battle from early detection to directing the fighters to intercept.

GCI systems grew in size and sophistication during the post-war era, in response to the overwhelming threat of nuclear attack. The US' [[Semi-Automatic Ground Environment|SAGE]] system was perhaps the most complex attempted, using building-filling computers linked to dozens of radars and other sensors to automate the entire task of identifying an enemy aircraft's track and directing [[interceptor aircraft]] or [[surface-to-air missile]]s against it. In some cases, SAGE sent commands directly to the aircraft's [[autopilot]], bringing the aircraft within attack range entirely under computer control. The RAF counterpart, [[ROTOR]] remained a mostly manual system.

Today, GCI is still important for most nations, although [[Airborne Early Warning and Control]], with or without support from GCI, generally offers much greater range due to the much more distant [[radar horizon]].

[[File:Chain home coverage.jpg|thumb|225px|upright|British [[Chain Home]] Radar Coverage 1939-1940]]