Date: 01/01/1983The Semi-Automatic Ground Environment (SAGE) was a system of large computers and associated networking equipment that coordinated data from many radar sites and processed it to produce a single unified image of the airspace over a wide area. SAGE directed and controlled the NORAD response to a Soviet air attack, operating in this role from the late 1950s into the 1980s. Its enormous computers and huge displays remain a part of cold war lore, and a common prop in movies such as Dr. Strangelove and Colossus. The processing power behind SAGE was supplied by the largest computer ever built, the AN/FSQ-7. Each SAGE Direction Center (DC) housed an FSQ-7 which occupied an entire floor, approximately 22,000 square feet not including supporting equipment. Information was fed to the DC’s from a network of radar stations as well as readiness information from various defence sites. The computers, based on the raw radar data, developed “tracks” for the reported targets, and automatically calculated which defences were within range. Operators used light guns to select targets onscreen for further information, select one of the available defences, and issue commands to attack. These commands would then be automatically sent to the defence site via teleprinter. Connecting the various sites was an enormous network of telephones, modems and teleprinters. Later additions to the system allowed SAGE’s tracking data to be sent directly to CIM-10 Bomarc missiles and some of the US Air Force’s interceptor aircraft in-flight, directly updating their autopilots to maintain an intercept course without operator intervention. Each DC also forwarded data to a Combat Center (CC) for “supervision of the several sectors within the division” (“each combat center had the capability to coordinate defense for the whole nation”).

SAGE became operational in the late 1950s and early 1960s at a combined cost of billions of dollars. It was noted that the deployment cost more than the Manhattan Project, which it was, in a way, defending against. Throughout its development there were continual questions about its real ability to deal with large attacks, and several tests by Strategic Air Command bombers suggested the system was “leaky”. Nevertheless, SAGE was the backbone of NORAD’s air defence system into the 1980s, by which time the tube-based FSQ-7’s were increasingly costly to maintain and completely outdated. Today the same command and control task is carried out by microcomputers, based on the same basic underlying data.

Earlier systems

Just prior to World War II, Royal Air Force tests with the new Chain Home (CH) radars had demonstrated that relaying information to the fighter aircraft directly from the radar sites was not feasible. The radars determined the map coordinates of the enemy, but could generally not see the fighters at the same time. Even if the information was accurate, it was difficult for the pilots to know where to turn to intercept their targets. The solution was to send all of the radar information to a central control station where operators collated the reports into single “tracks”, and then reported these tracks out to the airbases, or “sectors”. The sectors used additional systems to track their own aircraft, plotting both on a single large map. Operators viewing the map could then easily see what direction their fighters would have to fly to approach their targets, and relay that simply by telling them to fly along a certain heading. This Dowding system was the first ground controlled intercept system of large scale, covering the entirety of the UK. It proved enormously successful during the Battle of Britain, and is credited as being a key part in the RAF’s success.

However, the system was also slow, often providing information that was up to five minutes out of date. Against propeller driven bombers flying at perhaps 225 miles per hour (362 km/h) this was not a serious concern, but it was clear the system would be of little use against jet powered bombers flying at perhaps 600 miles per hour (970 km/h). The system was also extremely expensive in manpower terms, requiring hundreds of telephone operators, plotters, trackers and all of the radar operators on top of that. This was a serious drain on manpower reserves, making it difficult to expand the network. The idea of using a computer to handle the task of taking reports and developing tracks had been explored beginning late in the war. By 1944, analog computers had been installed at the CH stations to automatically convert radar readings into map locations, eliminating two people. Meanwhile, the Royal Navy began experimenting with the Comprehensive Display System (CDS), another analog computer that took X and Y locations from a map and automatically generated tracks from repeated inputs. Similar systems began development with the Royal Canadian Navy, DATAR, and the US Navy, the Naval Tactical Data System. A similar system was also specified for the Nike SAM project, specifically referring to a US version of CDS, coordinating the defense over a battle area so that multiple batteries did not fire on a single target. However, all of these systems were relatively small in geographic scale, generally tracking within a city-sized area.


Jay Forrester was instrumental in directing the development of the key concept of an interception system during his work at Servomechanisms Laboratory of MIT. The concept of the system, according to the Lincoln Laboratory site was to: develop a digital computer that could receive vast quantities of data from multiple radars and perform real-time processing to produce targeting information for intercepting aircraft and missiles

The AN/FSQ-7 was developed by the Lincoln Laboratory’s Digital Computer Laboratory and Division 6, working closely with IBM as the manufacturer. Each FSQ-7 actually consisted of two nearly identical computers operating in “duplex”[26] for redundancy. The design used an improved version of the Whirlwind I magnetic core memory and was an extension of the Whirlwind II computer program, renamed AN/FSQ-7 in 1953 to comply with Air Force nomenclature. It has been suggested the FSQ-7 was based on the IBM 701 but, while the 701 was investigated by MIT engineers, its design was ultimately rejected due to high error rates and generally being “inadequate to the task.” IBM’s contributions were essential to the success of the FSQ-7 but IBM benefited immensely from its association with the SAGE project, most evidently during development of the IBM 704. On October 28, 1953, the Air Force Council recommended 1955 funding for “ADC to convert to the Lincoln automated system”. The “experimental SAGE subsector, located in Lexington, Mass., was completed in 1955…with a prototype AN/FSQ-7…known as XD-1” (single computer system in Building F). In 1955, Air Force personnel began IBM training at the Kingston, New York, prototype facility, and the “4620th Air Defense Wing (experimental SAGE) was established at Lincoln Laboratory”

On May 3, 1956, General Partridge presented CINCNORAD’s Operational Concept for Control of Air Defense Weapons to the Armed Forces Policy Council, and a June 1956 symposium presentation identified advanced programming methods of SAGE code. For SAGE consulting Western Electric and Bell Telephone Laboratories formed the Air Defense Engineering Service (ADES), which was contracted in January 1954. IBM delivered the FSQ-7 computer’s prototype in June 1956, and Kingston’s XD-2 with dual computers guided a Cape Canaveral BOMARC to a successful aircraft intercept on August 7, 1958.:197 Initially contracted to RCA, the AN/FSQ-7 production units were started by IBM in 1958[citation needed] (32 DCs were planned:207 for networking NORAD regions.) IBM’s production contract developed 56 SAGE computers for $½ billion (~$18 million per computer pair in each FSQ-7)[—cf. the $2 billion WWII Manhattan Project.

General Operational Requirements (GOR) 79 and 97 were “the basic USAF documents guiding development and improvement of [the semi-automatic] ground environment. Prior to fielding the AN/FSQ-7 centrals, the USAF initially deployed “pre-SAGE semiautomatic intercept systems” (AN/GPA-37) to Air Defense Direction Centers, ADDCs (e.g., at “NORAD Control Centers”).  On April 22, 1958, NORAD approved Nike AADCPs to be collocated with the USAF manual ADDCs at Duncanville Air Force Station TX, Olathe Air Force Station KS, Belleville Air Force Station IL, and Osceola Air Force Station KS.


In 1957, SAGE System groundbreaking at McChord AFB was for DC-12 where the “electronic brain” began arriving in November 1958, and the “first SAGE regional battle post began operating in Syracuse, New York in early 1959”.[4]:263 BOMARC “crew training was activated January 1, 1958”, and AT&T “hardened many of its switching centers, putting them in deep underground bunkers”, The North American Defense Objectives Plan (NADOP 59-63) submitted to Canada in December 1958 scheduled 5 Direction Centers and 1 Combat Center to be complete in Fiscal Year 1959, 12 DCs and 3 CCs complete at the end of FY 60, 19 DC/4 CC FY 61, 25/6 FY 62, and 30/10 FY 63. On June 30 NORAD ordered that “Air Defense Sectors (SAGE) were to be designated as NORAD sectors”, (the military reorganization had begun when effective April 1, 1958, CONAD “designated four SAGE sectors — New York, Boston, Syracuse, and Washington — as CONAD Sectors”.)

SAGE Geographic Reorganization: The SAGE Geographic Reorganization Plan of July 25, 1958, by NORAD was “to provide a means for the orderly transition and phasing from the manual to the SAGE system.” The plan identified deactivation of the Eastern, Central, and Western Region/Defense Forces on July 1, 1960, and “current manual boundaries” were to be moved to the new “eight SAGE divisions” (1 in Canada, “the 35th”) as soon as possible. Manual divisions “not to get SAGE computers were to be phased out” along with their Manual Air Defense Control Centers at the headquarters base: “9th  Geiger Field… 32d, Syracuse AFS… 35th, Dobbins AFB… 58th, Wright-Patterson AFB… 85th, Andrews AFB”. The 26th SAGE Division (New York, Boston, Syracuse & Bangor SAGE sectors)–the 1st of the SAGE divisions—became operational at Hancock Field on 1 January 1959 after the redesignation started for AC&W Squadrons (e.g., the Highlands P-9 unit became the 646th Radar Squadron (SAGE) October 1.) Additional sectors included the Los Angeles Air Defense Sector (SAGE) designated in February 1959. A June 23 JCS memorandum approved the new “March 1959 Reorganization Plan” for HQ NORAD/CONAD/ADC.

Project Wild Goose teams of Air Material Command personnel installed c. 1960 the Ground Air Transmit Receive stations for the SAGE TDDL (in April 1961, Sault Ste Marie was the first operational sector with TDDL.) … By the middle of 1960, AMC had determined that about 800,000 man-hours (involving 130 changes) would be required to bring the F-106 fleet to the point where it would be a valuable adjunct to the air defense system. Part of the work (Project Broad Jump) was accomplished by Sacramento Air Materiel Area. The remainder (Project Wild Goose) was done at ADC bases by roving AMC field assistance teams supported by ADC maintenance personnel.  After a September 1959 experimental ATABE test between an “abbreviated” AN/FSQ-7 staged at Fort Banks and the Lexington XD-1, the 1961 “SAGE/Missile Master test program” conducted large-scale field testing of the ATABE “mathematical model” using radar tracks of actual SAC and ADC aircraft flying mock penetrations into defense sectors. Similarly conducted was the joint SAC-NORAD Sky Shield II exercise followed by Sky Shield III on 2 September 1962 On July 15, 1963, ESD’s CMC Management Office assumed “responsibilities in connection with BMEWS, Space Track, SAGE, and BUIC.” The Chidlaw Building’s computerized[specify] NORAD/ADC Combined Operations Center in 1963 became the highest echelon of the SAGE computer network when operations moved from Ent AFB’s 1954 manual Command Center to the partially underground “war room”. Also in 1963, radar stations were renumbered (e.g., Cambria AFS was redesignated from P-2 to Z-2 on July 31) and the vacuum-tube SAGE System was completed (and obsolete).

On “June 26, 1958,…the New York sector became operational” and on December 1, 1958, the Syracuse sector’s DC-03 was operational (“the SAGE system become operational until January 1959.”) Construction of CFB North Bay in Canada was started in 1959 for a bunker ~700 feet (210 m) underground (operational October 1, 1963), and by 1963 the system had 3 Combat Centers.