This research is concerned with Pakistan's participation in the US-led 'war on terror' in the aftermath of the terrorist attacks of September 11th, 2001. The study seeks to explain how Pakistan's state practice in the aftermath of 9/11 was normalised and made possible. In explaining the state practice, the study draws on a constructivist conceptual framework; which is further enhanced by incorporating key theoretical insights from critical realism. In the first instance, the study proposes that Pakistan's participation in the 'war on terror', seen as a set of actions and practices, was an outcome of a specific domestic political discourse. This discourse enabled and legitimised the state's alliance with the US and its abandonment of the Taliban regime. Secondly, the study is concerned with explaining why the particular discourse emerged in the shape and form that it did. In this context, the argument is that a depth 'critical realist' ontological inquiry can reveal underlying and enduring global and domestic social structural contexts, and traces of agential influence as connected to the discourse. Consequently, this study conceptualises Pakistan's actions in the context of the 'war on terror' as emerging from a multi-causal complex in which discourse, structure and agency are complicit. The study represents a departure from realist readings that emphasise a mono-causal relationship between the US and Pakistan. Instead, this research uses a synthesis of critical realism and constructivism to add a fresh perspective in terms of how we may conceptualise Pakistan's political practice in this instance.