“SAGE (Semi-Automatic Ground Environment) [was] the national air defense system implemented by the United States to warn of and intercept airborne attacks during the Cold War. The heart of this digital system—the AN/FSQ-7 computer—was developed, built and maintained by IBM. SAGE was the largest computer project in the world during the 1950s and took IBM squarely into the new world of computing.… SAGE spun off a large number of technological innovations that IBM incorporated into other computer products.

In June 1956, IBM delivered the prototype of the computer to be used in SAGE. The press release called it an “electronic brain.” It could automatically calculate the most effective use of missiles and aircraft to fend off attack, while providing the military commander with a view of an air battle. Although this seems routine in today’s world, it was an enormous leap forward in computing. When fully deployed in 1963, SAGE included 23 centers, each with its own AN/FSQ-7 system, which really consisted of two machines (one for backup), both operating in coordination. Ultimately, 54 systems were installed, all collaborating with each other. The SAGE system remained in service until January 1984, when it was replaced with a next-generation air defense network.

Its innovative technological contributions to IBM and the IT industry as a whole were significant. These included … real-time transmission of data over telephone lines; use of CRT terminals and light pens (a first) … It was the first geographically distributed, online, real-time application of digital computers in the world.”

IBM 100: Icons of Progress (via Brendan Simons)