During the early years of the Cold War, Canada and the United States began to develop a peacetime defence relationship. Initial co-operation was limited to the construction of minor installations and the creation of joint plans. But in 1950 both countries began to develop an air defence system to protect North America from the Soviet threat.

Securing the Continental Skies uses archival sources that have become available since the end of the Cold War to offer new insights into the development of the North American air defence system during the 1940s and 1950s. Matthew Trudgen analyzes the negotiations behind several recommendations from the Permanent Joint Board on Defence, three early-warning radar lines, and the North American Air Defence Command (NORAD). He argues that in Canada, air defence policy was shaped by different conceptions of the national interest among the Cabinet, the Department of External Affairs, the Royal Canadian Air Force, and the departments of Transport, Defence Production, and Northern Affairs and Natural Resources. In the United States, air defence policy reflected differing assessments of the importance of continental defence by the Truman and Eisenhower administrations. Ultimately North America's air defences were the outcome of a variety of factors, including Canadian political considerations and emerging nationalism, the state of Canada's electronics industry, the relationship between both countries' air forces, and American nuclear strategy.

Securing the Continental Skies challenges assumptions about Canadian foreign relations in the 1940s and 1950s and offers a new assessment of military co-operation between Canada and the United States.