The SOSUS (Sound Surveillance System) is a global chain of high-tech American sonar severance lines and clusters of underwater listening posts located in places around the world in places such as the Atlantic Ocean near Greenland, Iceland and the United Kingdom at the GIUK gap and at various locations in the Pacific Ocean.
It was planned out in in 1949, with formal development starting in 1950. It was started to be layed in 1952 and started work in 1961. The related Advanced Deployable System also became operational in 1996.
This can be seen as a less deadly aspect of the arms race.