Many states partially relinquish sovereignty in return for physical protection from a more powerful state. Mainstream theory on international hierarchies holds that such decisions are based on rational assessments of the relative qualities of the political order being offered. Such assessments, however, are bound to be contingent, and as such a reflection of the power to shape understandings of reality. Through a study of the remarkably persistent US-led security hierarchy in East Asia, this article puts forward the concept of the “epistemic community” as a general explanation of how such understandings are shaped and, hence, why states accept subordinate positions in international hierarchies. The article conceptualizes a transnational and multidisciplinary network of experts on international security—The Asia-Pacific Epistemic Community—and demonstrates how it operates to convince East Asian policymakers that the current US-led social order is the best choice for maintaining regional “stability.” The role of this community is illustrated using the recent US “pivot” to the Asia-Pacific—the biggest reinforcement of US security hierarchy in the region since the 1960s.