This thesis examines the theory and practice of humanitarian intervention in the early post-Cold War era. Taking as its basis US policy towards Somalia, Rwanda and Haiti between 1992 and 1994, it develops a theory of humanitarian intervention based on constructivist and scientific realist principles. Using identity as the organising concept, the thesis examines the meta-theoretical precepts of constructivism and scientific realism, which are developed into a methodology for analysing questions of foreign policy. Incorporating critical insights from sequential path analysis, morphogenetic social analysis - the notion of a dynamic mutual constitution of structure and agency - and constructivist social theory, the case studies provide a useful new means of conceptualising humanitarian intervention as a foreign policy practice through an identity-driven analysis. The findings of the research shed much light on this practice and its future prospects. They also suggest new directions for a scientific realist/constructivist research agenda.