These arrangements were confirmed and publicly proclaimed in 802, when Harun and the most powerful officials of the Abbasid government made the pilgrimage to Mecca. Al-Amin would succeed Harun in Baghdad, but al-Ma'mun would remain al-Amin's heir and would additionally rule over an enlarged Khurasan. This was an appointment of particular significance, as Khurasan had been the starting-point of the Abbasid Revolution which brought the Abbasids to power, and retained a privileged position among the Caliphate's provinces. Furthermore, the Abbasid dynasty relied heavily on Khurasanis as military leaders and administrators. Many of the original Khurasani Arab army ("Khurasaniyya") that came west with the Abbasids were given estates in Iraq and the new Abbasid capital, Baghdad, and became an elite group known as the "abnāʾ al-dawla" ("sons of the state/dynasty"). This large-scale presence of an Iranian element in the highest circles of the Abbasid state, with the Barmakid family as its most notable representatives, was certainly a factor in the appointment of al-Ma'mun, linked through his mother with the eastern Iranian provinces, as heir and governor of Khurasan. The stipulations of the agreement, which were recorded in detail by the historian al-Tabari, accorded al-Mamun's Khurasani viceroyalty extensive autonomy. However, modern historians consider that these accounts may have been distorted by later apologists of al-Ma'mun in the latter's favour. Harun's third heir, al-Mu'tamin, received responsibility over the frontier areas with the Byzantine Empire in Upper Mesopotamia and Syria.