the eastern half of the caliphate, al-Hajjaj ibn Yusuf, or the latter's kinsman Muhammad ibn Qasim. The Arab Muslim army had conquered the wider region of Fars, where the site of Shiraz is located, in several expeditions launched from their garrison town of Basra between 640 and 653, and specifically captured the immediate area around Shiraz early on, in 641. This area did not possess any cities, though there were a number of forts which were forced to pay tribute to the Arabs. The Sasanians held firm in Istakhr, their capital in Fars, until the Arabs captured it in a heavy battle in 653, during which the plain of Shiraz had been utilized as an Arab campground. Because of Istakhr's deep association with the Sasanian Empire and the Zoroastrian religion, the Arabs sought to establish in nearby Shiraz a rival cultural and administrative center. Thus, during its initial founding in 693, the city was planned to be much larger than Isfahan. However, the initial ambitions were not realized and Shiraz remained a "provincial backwater" in the shadow of Istakhr until at least the late 9th century, according to Limbert. This is partly attributed to the reticence of the largely Zoroastrian population of Fars to inhabit the Islamic Arab city. As the population gradually shifted to Islam from Zoroastrianism and Istakhr concurrently declined, Shiraz grew into the practical center of Fars. According to Muslim traditional sources, Shiraz was used as a hideout by three of the brothers of the Shia Muslim imam Ali al-Ridha following the latter's death in 817/18 and later by one of the brothers' sons, Ali ibn Hamza ibn Musa, until he was found and executed by the Abbasid authorities in circa 835. As Abbasid authority waned during this period, regional dynasties emerged with considerable autonomy. In the late 9th century, the Iranian Muslim Saffarid dynasty under Ya'qub ibn al-Layth made Shiraz the capital of their autonomous state, which encompassed most of modern-day Iran. In 894, Ya'qub's brother and successor, Amr, founded the city's first congregational mosque, today known as the Atigh Jame' Mosque. The Iranian Buyid dynasty under Imad al-Dawla Ali ibn Buya ousted the Saffarids in 933 and his nephew and successor, 'Adud al-Dawla Fana Khusraw, took over and ruled Fars between 949 and 983, and added Iraq, the seat of the Abbasid Caliphate, to his Shiraz-based domains in 977; the Abbasids thenceforth became a puppet