 In 969 they conquered Egypt and established Cairo as the capital of their caliphate; Egypt became the political, cultural, and religious centre of their empire that developed a new, indigenous Arabic culture.The ruling class belonged to the Ismai'li branch of Shi'a Islam, as did the leaders of the dynasty.The existence of the caliphate marked the only time the descendants of Ali and Fatimah were united to any degree (except for the final period of the Rashidun Caliphate under Ali himself from 656 to 661) and the name "Fatimid" refers to Fatimah.