This article analyses the competing security perspectives of hemispheric and South American defence cooperation initiatives. While the Organization of American States (OAS) emphasises domestic roles for armed forces in the region, concentrating on internal threats such as organised crime and terrorism, the South American Defence Council (CDS) emphasises the traditional conception of security, concentrating on the defence of sovereign states against external military threats. Despite its apparent consistency, the concept of deterrent cooperation has not taken hold. While the literature interprets this failure as a cooperation problem, I argue that it is due to a deeper regional trend, namely the tendency to neglect external defence in favour of internal security roles for armed forces. After building a conceptual framework for clarifying these divergent perspectives, I show how they define the activities of the two competing organisations. Next, I address the conflict between the CDS’s conception of security and the security policies of OAS member states. Finally, I discuss domestic and structural obstacles to the adoption of common Latin American defence policies.