The first change made by the Abbasids under Al-Mansur was to move the empire's capital from Damascus to a newly founded city. Established on the Tigris River in 762, Baghdad was closer to the Persian "mawali" support base of the Abbasids, and this move addressed their demand for less Arab dominance in the empire. A new position, that of the vizier, was also established to delegate central authority, and even greater authority was delegated to local emirs. Caliph al-Mansur centralised the judicial administration, and later, Harun al-Rashid established the institution of Chief Qadi to oversee it.