Canada and SOSUS
The Sound Surveillance System (SOSUS) was a network of passive sonar stations established by the United States Navy (USN) in the early 1950s to “listen” for Soviet submarines. SOSUS was a core element of antisubmarine warfare (ASW) during the Cold War. It developed out of intense postwar oceanographic research into how sound is propagated under water. Given Canada’s shared responsibility for the defence of North America, the Royal Canadian Navy (RCN) was actively engaged in this research and mission and helped operate SOSUS. The mission was highly classified throughout the Cold War and only declassified in 1991. SOSUS became part of the Integrated Undersea Surveillance System (IUSS), a broader network of fixed and towed sensors that remains operational.