 Pagan's 250-year rule over the Irrawaddy valley and its periphery laid the foundation for the ascent of Burmese language and culture, the spread of Burman ethnicity in Upper Burma, and the growth of Theravada Buddhism in Burma and in mainland Southeast Asia.The kingdom grew out of a small 9th-century settlement at Pagan (Bagan) by the Mranma (Burmans), who had recently entered the Irrawaddy valley from the Kingdom of Nanzhao.Over the next two hundred years, the small principality gradually grew to absorb its surrounding regions until the 1050s and 1060s when King Anawrahta founded the Pagan Empire, for the first time unifying under one polity the Irrawaddy valley and its periphery.