Every documented way of life rooted in noble principles, goes through an era of prolific development and expansion, and settles into resilient stability as the wheel of time turns the world around. Buddhism is no exception to this seemingly universal cycle. From its popularization and glorious suffusion through the veins of Bharat to its expansion in the adjacent geographical regions, progression of Buddhist culture is a reflection of the impact of socio-political shifts on a civilization. During the mentioned period, while Buddhism was experiencing an inevitable decline in India due to foreign invasions, it was flourishing and becoming culturally rich in other countries of Asia. As a matter of fact, Buddhism has evolved into the primary religion of these neighbouring countries such as Tibet, Japan, Myanmar, Thailand, Vietnam, and Cambodia rather than in the birth place of Buddha himself. The very essence of Buddhism underwent spiritual, literary, artistic, and philosophical developments in due course of time. This chapter is aimed at exploring and documenting the ascension of Buddhism and its consequent demographic impact based on architectural and literary evidences from early medieval age in Asia.