This study revisits one of the most extensive examples of the spread of ideas in the history of civilisation: 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 legitimise 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 ""colonisation"" 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. It challenges the view that strategic competition is a recurring phenomenon when civilisations encounter each other.