This study revisits one of the most extensive examples of the spread of ideas in the history of civilization: the diffusion of Indian religious and political ideas to Southeast Asia before the advent of Islam and European colonialism. Hindu and Buddhist concepts and symbols of kingship and statecraft helped to legitimize Southeast Asian rulers, and transform the political institutions and authority of Southeast Asia. But the process of this diffusion was not accompanied by imperialism, political hegemony, or “colonization” as conventionally understood. This book investigates different explanations of the spread of Indian ideas offered by scholars, including why and how it occurred and what were its key political and institutional outcomes. My purpose is not to offer an exhaustive account of Indian cultural impact on Southeast Asia, but to draw specific insights from this diffusion to challenge the view that strategic competition is a recurring phenomenon when civilizations encounter each other. It is also to advance the case for considering alternative models of diffusion of ideas and culture in world politics. In essence, I highlight a powerful historical precedent for inter-civilizational convergence that upholds the agency of the local actors and debunks the notion that the diffusion of ideas can only occur through the mechanisms of power politics.