This article attempts to fill a gap in International Relations (IR) literature on East Asian security. ‘East Asia’ appears to be mostly an indeterminate conceptual construct, allowing scholars to look selectively at those aspects and areas that could justify their security thesis, albeit security dynamics in the region are all too difficult to comprehend and predict. This problem has been frequently pointed out in IR literature, but its methodological implications and suggestions have neither been appropriately illuminated nor been systematically offered, and the main solution commonly found in the literature was the tautological one of ‘better defining’ the region. As an alternative, this article suggests that one needs to tighten geographical focus and differentiate the subjects of analysis. When it comes to the study of East Asian security, one needs to aim to develop specific and differentiated generalizations as opposed to generalizations of a broad character. To showcase the fact that research outcomes can be more determinate when the target of analysis is more focused and specified, this article takes Northeast Asian security as an example and challenges the so-called ‘peaceful East Asia’ thesis, one of the mainstream perspectives on East Asian security. This article ultimately argues that while apprehending East Asian security dynamics through delimiting the scope of analysis and circumscribing the subjects of investigation is often deemed to be a modest enterprise―in particular, in terms of generalizability―the merits are substantial: research outcomes will be able not only to give us a truer mapping of the real world, but also bring us closer to building knowledge which satisfies the scientific criterion of ‘falsifiability.’