The 1940 Ogdensburg Agreement entrenched a formal defence relationship between Canada and the United States. But was Canadian sovereignty upheld? Drawing on untapped archival material, Sovereignty and Command in Canada–US Continental Air Defence, 1940–57 documents the close and sometimes fractious relationship between the two countries. Richard Goette challenges prevailing perceptions that Canada’s defence relationship with the United States eroded Canadian sovereignty. He argues instead that a functional military transition from an air defence system based on cooperation to one based on integrated and centralized command and control under NORAD allowed Canada to retain command of its forces and thus protect Canadian sovereignty. Goette combines historical narrative with conceptual analysis of sovereignty, command and control systems, military professionalism, and civil-military relations. In the process, he provides essential insights into the Royal Canadian Air Force’s paradigm shift away from its Royal Air Force roots toward closer ties with the United States Air Force and the role of the nation’s armed forces in safeguarding its sovereignty.