The rise of the Buyids at a particular point in Iran's history gave the structure of this government a great deal of potential for social change. The rule of the Buyids was shaped during the time that the ʿAbbāsid Caliphate had changed from being a dominant structure in the Islamic world to being a limited power in Baghdad and in the surrounding towns. Only a few local dynasties in Iran, including the Sāmānids, still valued the caliph's mandate and based their structure's legitimacy on the caliph's approval. Amir al-ʾOmarā of Baghdad, who was of Turkish descent, played a crucial role in the caliph's death and life as the most remarkable figure in the Islamic world. At the same time, the rise of local dynasties, including the Ziyārids, was shaped outside the caliphate's framework. Even their founders thought of dominating Baghdad, which posed a great challenge to the ʿAbbāsid Caliphate. This was because the ʿAbbāsid caliph had the Fatimid Caliphate as its main rival, which, unlike many local dynasties, was not content with the established division of power with the ʿAbbāsid caliph. The Fatimids defined a new legitimacy that endangered the resources of the ʿAbbāsid power. The Buyids, whose power was derived from the military might of the Deylamites, succeeded in establishing a government in Iran using historical conditions, but their social changes influenced the course of post-Buyid dynasties, namely the Saljuqs.