Abu'l-Abbas Ahmad ibn Ishaq (; 947/8 – 29 November 1031), better known by his regnal name al-Qadir (), was the Abbasid caliph in Baghdad from 991 to 1031. He was the grandson of al-Muqtadir, and was chosen in place of the deposed caliph, at-Ta'i, his cousin. His reign was marked by the strengthening of the Abbasid caliphate's role as the champion of Sunni Islam against Shia Islam, notably through the Baghdad Manifesto of 1011, and through the codification, for the first time, of Sunni doctrines and practices in the , thereby presaging the "Sunni Revival" later in the century. Early life Abu'l-Abbas Ahmad, the future al-Qadir, was born on 28 September 947 in Baghdad. His father Ishaq was a son of Caliph al-Muqtadir (), and his mother Dimna was a slave concubine. Shortly before his birth, in December 945, Baghdad and the rest of Iraq had been taken over by the Buyids. Although the Buyids were pro-Shi'a, they had retained the Abbasid caliphate for reasons of legitimacy. The Buyids ruled Iraq ostensibly as caliphal commander-in-chiefs (), but in practice they had reduced the Abbasid caliphs to puppet rulers, confined to their palaces. As an Abbasid prince, Ahmad received a good education; he is recorded as having collected Shafi'i works on jurisprudence () by Ahmad ibn Muhammad al-Harawi. When his father Ishaq died in March 988, Ahmad quarreled with his half-sister, Amina, over the inheritance. She reported him to their cousin, Caliph al-Ta'i (), as seeking to replace him as caliph. To escape capture, Ahmad went into hiding for a while, before seeking refuge with the governor of the swamps of Bathihah near Basra, Muhadhdhib al-Dawla, for about three years. From there, Ahmad plotted against al-Ta'i, harping on his own loyalty to the Buyids, whereas al-Ta'i had been installed by a Turkic general, Sabuktakin. Caliphate In 991, the Buyid ruler Baha al-Dawla deposed al-Ta'i, because the latter had been showing signs of independence. In his stead, Baha al-Dawla appointed al-Qadir to the caliphate on 22 November 991 (12 Ramadan 381 AH). The deposed al-Ta'i was kept in captivity until his death twelve years later. Despite their previous differences, al-Qadir treated his predecessor well: al-Ta'i was not blinded, as had been the case for previous deposed caliphs, and he was accorded the treatment due to a reigning caliph. Early years At first, the new caliph seemed obedient, approving the nominations of officials