Since around 500 B.C. Asia's expanding land and maritime trade had led to socio-economic interaction and cultural stimulation and diffusion of mainly Hindu beliefs into the regional cosmology of Southeast Asia. Iron Age trade expansion caused regional geostrategic remodelling. Southeast Asia was now situated in the central area of convergence of the Indian and the East Asian maritime trade routes, the basis for economic and cultural growth. The concept of the "Indianised kingdoms", a term coined by George Coedès, describes Southeast Asian principalities that since the early common era as a result of prolonged interaction had incorporated central aspects of Indian institutions, religion, statecraft, administration, culture, epigraphy, writing and architecture.