Baha' Al-Daula

Baha' al-Daula (died December 22, 1012) was the Buyid amir of Iraq (988–1012), along with Fars and Kerman (998–1012). He was the third son of 'Adud al-Daula.

Upon the death of his brother Sharaf al-Daula in 988, Baha' al-Daula succeeded him, whereupon he took the additional title of "Diya' al-Milla". Another brother, Samsam al-Daula, prevented Baha' al-Daula from gaining all of Sharaf al-Daula's possessions by taking control of Fars, Kerman and Khuzestan. Both Baha' al-Daula and his brother, however, were threatened by their granduncle Fakhr al-Daula, who was the ruler of Jibal. Fakr al-Daula invaded Khuzestan in an attempt to split the two brothers' territories. This act prompted the brothers to draw up an alliance. Samsam al-Daula recognized Baha' al-Daula as the ruler of Iraq and Khuzestan, while he himself kept Arrajan, Fars and Kerman. Both promised to consider each other as equals, and took the title of "king".

In 991 Baha' al-Daula attempted to gain supremacy over Samsam al-Daula's realm. He took the title of Shâhanshâh and invaded the latter's territory. His forces were defeated, however, and Samsam al-Daula regained Khuzestan, and even gained control of the Buyid territories in Oman. He then recognized Fakhr al-Daula as senior amir, submitting to his authority.

Fakhr al-Daula's death in 997, coupled with Samsam al-Daula's increasing troubles within his realm, provided Baha' al-Daula with the opportunity to assert his authority in Persia. He gained the support of the Kurdish ruler Badr ibn Hasanwaih and prepared for the expedition. The invasion began in December of 998; scarcely had it commenced when Samsam al-Daula was killed by one of the sons of 'Izz al-Daula who had risen in revolt. Baha' al-Daula took Shiraz and defeated 'Izz al-Daula's sons. For the rest of his life Baha' al-Daula remained in Fars. He also managed to gain indirect control over northern Iran, where Fakr al-Daula's two sons Majd al-Daula and Shams al-Daula recognized him as senior amir by 1009 or 1010.

Baha' al-Daula's reign coincided with the beginning of the decline of the Buyids. A Kurdish chief, Badr, laid the foundations for the Marwanid amirate in Diyarbakr, while the initially subservient 'Uqailids of Mosul expanded into Iraq at the Buyid's expense. By the time Baha' al-Daula died, Baghdad and Wasit were the only two major Iraqi cities directly under his control. In the north, where Fakhr al-Daula's sons ruled, the Buyid frontier also fell back. The Ziyarids of Gorgan and Tabaristan permanently wrested themselves from Buyid control. The Ghaznavids kept putting pressure on the Khurasan border, while the Kakuyids began to set up a state in Isfahan.

For various reasons, Baha' al-Daula did not actively defend the borders. Having gained undisputed control of the Buyid state, he seemed content to allow external enemies to seize territories in the west and north. He died in Arrajan in December of 1012. Shortly before his death, he named his son Sultan al-Daula as his successor.