Editing Al-Ma'mun (section)

==Appointment as successor and Governor of Khurasan==
Although Abdallah was the oldest of his sons, in 794 Harun named the second-born Muhammad, born in April 787 to Zubayda, as the first in line of succession. This was the result of family pressure on the Caliph, reflecting Muhammad's higher birth, as both parents descended from the Abbasid dynasty; indeed, he remained the only Abbasid caliph to claim such descent. Muhammad received the oath of allegiance (''[[bay'ah]]'') with the name of [[al-Amin]] ("The Trustworthy"), first in [[Khurasan]] by his guardian, the [[Barmakid]] [[al-Fadl ibn Yahya]], and then in [[Baghdad]].{{sfn|Rekaya|1991|p=331}} Abdallah was recognized as second heir only after entering puberty, in 799, under the name al-Ma'mun ("The Trusted One"), with another Barmakid, [[Ja'far ibn Yahya]], as his guardian. At the same time, a third heir, [[al-Qasim ibn Harun al-Rashid|al-Qasim]], named al-Mu'tamin, was appointed, under the guardianship of [[Abd al-Malik ibn Salih]].{{sfn|Rekaya|1991|p=331}}

These arrangements were confirmed and publicly proclaimed in 802, when Harun and the most powerful officials of the Abbasid government made the [[hajj|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]].{{sfn|Rekaya|1991|p=331}} 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 [[Mesopotamia|Iraq]] and the new Abbasid capital, Baghdad, and became an elite group known as the ''[[abna al-dawla|abnāʾ al-dawla]]'' ("sons of the state/dynasty").{{sfn|El-Hibri|2010|p=274}}{{sfn|Kennedy|2004|pp=133–135}} This large-scale presence of an [[Iranian peoples|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.{{sfn|El-Hibri|2010|p=282}} 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.{{sfn|El-Hibri|2010|pp=282–283}} Harun's third heir, al-Mu'tamin, received responsibility over the [[al-'Awasim|frontier areas]] with the [[Byzantine Empire under the Nikephorian dynasty|Byzantine Empire]] in [[al-Jazira (caliphal province)|Upper Mesopotamia]] and [[Bilad al-Sham|Syria]].{{sfn|Rekaya|1991|p=331}}{{sfn|Kennedy|2004|p=142}}

Very quickly, the latent rivalry between the two brothers had important repercussions: almost immediately after the court returned to Baghdad in January 803, the Abbasid elites were shaken by the abrupt fall of the Barmakid family from power. On the one hand, this event may reflect the fact that the Barmakids had become indeed too powerful for the Caliph's liking, but its timing suggests that it was tied to the succession issue as well: with al-Amin siding with the ''abnāʾ'' and al-Ma'mun with the Barmakids, and the two camps becoming more estranged every day, if al-Amin was to have a chance to succeed, the power of the Barmakids had to be broken.{{sfn|Rekaya|1991|p=331}}{{sfn|Kennedy|2004|pp=142–143}}{{sfn|El-Hibri|2010|p=283}}

[[Al-Fadl ibn Sahl]], a [[Kufa]]n of Iranian origin whose father had converted to Islam and entered Barmakid service, replaced Ja'far ibn Yahya as al-Ma'mun's tutor. In 806 he also became al-Ma'mun's secretary (''[[katib]]''), an appointment that marked him out as the chief candidate for the [[Vizier (Abbasid Caliphate)|vizier]]ate should al-Ma'mun succeed to the throne.{{sfn|Rekaya|1991|p=331}} In 804, al-Ma'mun married his cousin, Umm Isa, a daughter of the Caliph [[al-Hadi]] ({{reign|785|786}}). The couple had two sons, Muhammad al-Asghar and Abdallah.{{sfn|Rekaya|1991|p=331}}

The years after the fall of the Barmakids saw an increasing centralization of the administration and the concomitant rise of the influence of the ''abnāʾ'', many of whom were now dispatched to take up positions as provincial governors and bring these provinces under closer control from Baghdad.{{sfn|El-Hibri|2010|p=283}} This led to unrest in the provinces, especially Khurasan, where local elites had a long-standing rivalry with the ''aabnāʾ'' and their tendency to control the province (and its revenues) from Iraq.{{sfn|Kennedy|2004|p=144}} The harsh taxation imposed by a prominent member of the ''abnāʾ'', [[Ali ibn Isa ibn Mahan]], even led to a revolt under [[Rafi ibn al-Layth]], which eventually forced Harun himself, accompanied by al-Ma'mun and the powerful chamberlain (''[[hajib]]'') and chief minister [[al-Fadl ibn al-Rabi]], to travel to the province in 808. Al-Ma'mun was sent ahead with part of the army to [[Merv]], while Harun stayed at [[Tus, Iran|Tus]], where he died on 24 March 809.{{sfn|Rekaya|1991|p=331}}{{sfn|El-Hibri|2010|p=283}}{{sfn|Kennedy|2004|pp=144–145}}