Since the mid-1950s, successive Canadian governments have responded to US ballistic missile defence initiatives with fear and uncertainty. Officials have endlessly debated the implications – at home and abroad – of participation. Drawing on previously classified government documents and interviews with senior officials, James Fergusson offers the first full account of Canada’s unsure response to US initiatives. He reveals that factors such as weak leadership and a tendency to place uncertain and ill-defined notions of international peace and security before national defence have resulted in indecision. In the end, policy-makers have failed to transform the ballistic missile defence issue into an opportunity to define Canada’s strategic interests at home and on the world stage.