What was the purpose of the Distant Early Warning Line established in Canada's north?

The Distant Early Warning Line, commonly referred to as the DEW Line, was established during the Cold War as a crucial component of North American defense strategy. Its primary purpose was to detect Soviet bombers or missiles approaching North America, particularly from the Arctic region. The DEW Line consisted of a series of radar stations located in the northern parts of Canada and Alaska, allowing for early warning of any potential airborne threats. This system was critical for ensuring national security during a time of heightened tensions between the United States and the Soviet Union.

The other options, while they may seem plausible in different contexts, do not align with the historical and strategic objectives of the DEW Line. Monitoring whales and protecting endangered species address environmental concerns rather than defense mechanisms. Guiding air traffic relates to civilian aviation and safety, which is outside the military focus of the DEW Line's establishment and function. Thus, the option regarding the detection of Soviet bombers or missiles is the correct one, as it captures the essential rationale for the DEW Line's creation.