The Abbasid leadership had to work hard in the last half of the 8th century (750–800) under several competent caliphs and their viziers to overcome the political challenges created by the far-flung nature of the empire and the limited communication across it and usher in the administrative changes needed to keep order.^[34] It was also during this early period of the dynasty, in particular during the governance of al-Mansur, Harun al-Rashid, and al-Ma'mun, that the reputation and power of the dynasty was created.^[2]