The Buyid confederation existed within the Islamic empire from 945 to 1055. They were originally part of the Daylamite peoples of Gilan and Daylam in northern Iran. In pre_Islamic times they had served as mercenaries for the Sasanian kings of Iran, but were independent from their rule. They were considered a formidable military force, especially their ability as foot soldiers. Succession of power was hereditary, fathers dividing their land among their sons. During the time of Harun al-Rashid, the Alid people sought refuge among them.
The start of the Buyid confederation was led by Ali b. Buya and his two younger brothers, al_Hasan and Ahmad. After having secured a partnership with an important Persian landowner named Zayd b. Ali al-Nawbandajani, Ali was able to recruit an army to defeat a Turkish general from Baghdad named Yaqut in 934. After that they established power within the crumbling Abbasid empire in the form of a confederation rather than a new empire. They were known for the revival of Persian culture. Buyid leaders were known as Shâhanshâh (شاهنشاه), literally king of kings.
The Buyids had Shiite leanings, and it was during their period of rule that the Sunni-Shiite divide in Islam became fully established and Shiism developed its distinct sectarian character.
Buyid officials intermittently patronized the Shiites in Baghdad and encouraged their developing into an armed political group that fought it out with Sunni groups.
The Buyids took the region of Mosul from the Hamdanids in 979, but in 990 the Uqayli Arab tribe established itself there, after a short-lived attempt by the Hamdanids to restore their rule.
With the capture of the Abbasid capital, Baghdad, in 945, the Buyids assumed control of the Abassid Empire.
Buyid control peaked during the reign (94983) of Adud ad-Dawlah, who increased the dynasty's territorial domain, adding Oman, Tabaristan, and Jorjan.
Discord among later Buyid leaders led to the eventual decline of their power by 1060; they were replaced by other dynasties, who divided Buyid territory.