Distant Early Warning Line

The Distant Early Warning Line, also known as the DEW Line or Early Warning Line, was a system of radar stations in the northern Arctic region of Canada, with additional stations along the north coast and Aleutian Islands of Alaska (see Project Stretchout and Project Bluegrass), in addition to the Faroe Islands, Greenland, and Iceland (DYE Stations). It was set up to detect incoming bombers of the Soviet Union during the Cold War, and provide early warning of any sea-and-land invasion.

Source: Wikipedia — Distant Early Warning Line (CC BY-SA 4.0)