 The Buyids, who were Zaidi and had a significant influence not only in the provinces of Persia but also in the capital of the caliphate in Baghdad, and even upon the caliph himself, provided a unique opportunity for the spread and diffusion of Shia thought.This spread of Shiism to the inner circles of the government enabled the Shia to withstand those who opposed them by relying upon the power of the caliphate.Twelvers came to Iran from Arab regions in the course of four stages.