Minimum Essential Emergency Communications Network
A collection of 23 radio, wired, and switched network, the Minimum Essential Emergency Communications Network (MEECN) was established, in the 1970s, as a means of reliably communicating with U.S. military forces under conditions of nuclear war. While there are persistent rumors that the Internet and its predecessors were designed for the nuclear communications mission, this is not the case; packet switching was insufficiently mature at the time.
The system included fairly obvious components such as the Department of Defense message switching system, AUTODIN, as well as well-known radio communications such as the high-frequency single-sideband radio broadcast system of the Strategic Air Command. Other systems were secret at the time, but now have been declassified, such as the Emergency Rocket Communications System (ERCS), which consisted of UHF transmitters that replaced the warheads in three LGM-30 Minuteman intercontinental ballistic missiles. Another, CLARINET PILGRIM, was a clandestine transmission channel to submarines, overlaid onto LORAN navigational signals.