and its AI Mk. IV radar which became available in numbers at the same time. These two systems proved to be a potent combination, and interception rates doubled every month from January 1941 until the Luftwaffe campaign ended in May. The Germans were quite slow to follow in terms of PPI and did not order operational versions of their Jagdschloss radar until late in 1943, with deliveries being relatively slow after that. Many were still under construction when the war ended in 1945. Post WWII More recently, in both the Korean and Vietnam wars, the North Koreans and North Vietnamese had important GCI systems which helped them harass the opposing forces (although in both cases due to the superiority in the number of US planes the effect was eventually minimised ). GCI was important to the US and allied forces during these conflicts also, although not so much as for their opponents. The most advanced GCI system deployed to date was the US's Semi Automatic Ground Environment (SAGE) system. SAGE used massive computers to combine reports sent in via teleprinter from the Pinetree Line and other radar networks to produce a picture of all of the air traffic in a particular "sector"s area. The information was then displayed on terminals in the building, allowing operators to pick defensive assets (fighters and missiles) to be directed onto the target simply by selecting them on the terminal. Messages would then automatically be routed back out via teleprinter to the fighter airbases with interception instructions on them. The system was later upgraded to relay directional information directly to the autopilots of the interceptor aircraft like the F-106 Delta Dart. The pilot was tasked primarily with getting the aircraft into the air (and back), and then flying in a parking orbit until called for. When an interception mission started, the SAGE computers automatically flew the plane into range of the target, allowing the pilot to concentrate solely on operating the complex onboard radar. The RAF's post-war system was originally ROTOR, which was largely an expanded and rationalized version of their wartime system and remained entirely manual in operation. This was upset by the introduction of the AMES Type 80 radar, which was originally intended as a very long-range early warning system for ROTOR but demonstrated its ability to control interceptions as well. This led to the abandonment of the ROTOR network and its operation