After the end of the Cold War realism was the most sceptical theory insofar as NATO’s endurance in the post-Cold War period was concerned. In fact, realist thinkers were in doubt as to what NATO’s purpose would be without a common enemy such as the Soviet Union (USSR) which had catalysed the attention of the transatlantic allies during the long decades of the Cold War. Furthermore, the realist explanation of NATO has consistently been under attack by other international relations (IR) paradigms such as liberal institutionalism and social constructivism which claim to have a better and sounder explanation for NATO’s endurance and transformation in the post-Cold War period. This paper posits the question whether realism’s failure to predict NATO’s future and the emergence of alternative explanations represents evidence that realism ‘as a whole’ got it wrong. The paper tackles this question by reviewing three main variants of the realist theory which have developed in the post-Cold War period and which all claim to explain NATO’s purpose in the 21st century. Precisely, these are the offensive, defensive and neoclassical realist explanations. It is argued that by moving beyond a threat-based and in favour of a power projection approach, realist theories have sought to explicate NATO’s transformation by focusing on the USA’s responses to the different incentives of the post-Cold War unipolar world but offered different policy prescriptions.
