EEDSP

The Semi-Automatic Ground Environment (SAGE) was a Cold War operator environment for the automated air defense (AD) of North America and by extension, the name of the network of computer systems providing the ground environment for the larger air defense system with buildings, radars, and defense aircraft. SAGE Direction Centers (DC) in large "cube" buildings provided radar netting for Air Defense Sectors using data from numerous remote Air Force Stations each manned by SAGE radar squadrons operating several radars for searching/detecting, height finding, and for automatic tracking of Bomarc missiles. Each SAGE DC provided data to a Combat Center for "supervision of the several sectors within the division"^[8] ("each combat center [had] the capability to coordinate defense for the whole nation").^[9]:51

Computerized command and control for United States air defense was conceived in July 1945 during the Signal Corps' Project 414A contracted to Bell Laboratories^[10]:207 after the CONUS WWII Army Radar Stations closed in 1944 (stations were networked by manual Aircraft Warning Corps' "information centers").^[11] Replacing the manual 1948 "five-station radar net" and the Lashup Radar Network (completed April 1950) was a Priority Permanent System with the initial (priority) radar stations completed in 1952^[3]:223 as a "manual air defense system"^[5] (e.g., NORAD/ADC used a Plexiglas plotting board at the Ent AFB command center.) The Permanent System added 3 phases of semimobile radars and "at the end of 1957, ADC operated 182 radar stations [and] 17 control centers … 32 [stations] had been added during the last half of the year as low-altitude, unmanned gap-filler radars. The total consisted of 47 gap-filler stations, 75 Permanent System radars, 39 semimobile radars, 19 Pinetree stations,…1 Lashup station [and a] single Texas Tower".^[3]:223

The December 1949 "Air Defense Systems Engineering Committee" led by Dr. George Valley had recommended computerized networking^[12] for "radar stations guarding the northern air approaches to the United States",^[13] including some stations in Canada. In 1949 the USAF had funded Project Charles to develop a demonstration system for automating Air Defense^{[citation needed]} and after a January 1950 meeting, Valley and Jay Forrester proposed using the Whirlwind I (built 1948-51) for air defense. The Cape Cod System at Cambridge, Massachusetts, was the "first major Lincoln Laboratory effort"^[14] and networked long-range and several short-range radars. On August 18, 1950, when the "1954 Interceptor" requirements were issued, the USAF "noted that manual techniques of aircraft warning and control would impose “intol­erable” delays."^[15]:484 Between February and August 1951, the USAF conducted Project Claude at the 1951 MIT Lincoln Laboratory and which concluded an improved air defense system was needed.^{[citation needed]}