This thesis examines the reconstruction of the North Atlantic Treaty Organisation (NATO) since the end of the Cold War. Conventional knowledge in International Relations argues that alliances should dissolve with the disappearance of the military threat which they were created to address. But NATO still exists and has engaged in new activities that depart from its original purpose - specifically, engaging in crisis management beyond its territorial boundary. How is it possible to explain this shift in NATO's purpose and its transformation from an anti-Communist alliance into one that is concerned with humanitarian crises? The thesis analyses this question by posing a view, based on constructivism, that 'international' organisations are developed as state leaders try to meet 'domestic' normative concerns.