This dissertation examines the evolution of the bilateral Canadian-American continental air defence operational-level command and control relationship from the 1940 Ogdensburg Agreement to the establishment of the North American Air Defence Command (NORAD) in 1957. It takes a functional approach, focusing on the efforts of Canadian air force officers in conjunction with their American counterparts to develop efficient command and control arrangements to ensure effective air defence of North America while at the same time safeguarding Canadian sovereignty. It explores the evolution of certain command and control principles such as cooperation, unity of command, operational command, and operational control, and argues that because Canada was able to avoid having its air defence forces come under American command, Canadian sovereignty was assured. It also demonstrates that the Canada-U.S. bilateral continental air defence command and control relationship had its origins in Canadian, American, and British joint command and control culture and practice. Canadian steadfastness, along with compromise and accommodation between the two North American nations, operational and doctrinal factors, and also cordial professional working relationships and personalities, all played important roles in the evolution of this command and control relationship from the "cooperation-unity of command" paradigm of the Second World War towards "operational control" in an air defence context throughout the early Cold War. This paradigm shift culminated in 1957 with the integration and centralization of combined air defences under an overall NORAD commander exercising operational control. The thesis also demonstrates that by taking an active role in Canada-U.S. command and control arrangements, Canada was able to avoid a negative "defence against help" situation with the United States and ensure that it secured a proverbial "piece of the action" in the bilateral North American continental air d.