In this year al-Amin dismissed his brother al-Qasim from the governorship of al-Jazirah and the frontier districts, appointing Khuzaymah b. Khazim in his place, and ordered his brother to stay with him in Baghdad.

That same year al-Amin commanded that sermons throughout every province include prayers for his son Musa, naming him heir apparent and conferring upon him the title al-Natiq bil-Haqq (the Speaker of Truth). After Musa the prayer was to be for his brother al-Maʾmun, and then for his brother al-Qasim.

Al-Amin had originally intended to honor the pledges made to his two brothers, but al-Faḍl b. al-Rabiʿ persisted until he changed his mind, urging him to depose al-Maʾmun and al-Qasim and belittling al-Maʾmun’s stature. What moved him was his fear that, were the caliphate to devolve upon al-Maʾmun, he would strip him of the chamberlainship (ḥijābah) (1). Al-Amin agreed and ordered that the public invocation be restricted to his son Musa and that the succession be assigned to him. This took place in Rabīʿ al-Awwal of the present year.

When word reached al-Maʾmun, he severed the postal route to al-Amin, ceased striking his name on the coinage and the official embroideries, and adopted an attitude of estrangement toward him. Rāfiʿ b. al-Layth wrote to al-Maʾmun requesting safe-conduct; al-Maʾmun granted it, whereupon he came to him with his followers, and al-Maʾmun received him with honor and distinction. Shortly thereafter Harthama arrived; al-Maʾmun and the leading men went out to meet him, and al-Maʾmun appointed him commander of the guard.

When al-Amin learned that the troops had rallied around his brother al-Maʾmun he was troubled and dismayed. He wrote to al-Maʾmun and dispatched three prominent commanders as envoys, asking him to yield precedence to his son and reminding him that he had already named him al-Natiq bil-Haqq. Al-Maʾmun showed refusal, so the commanders began coaxing and conciliating him, but he refused outright.

At that, ʿAbbās b. Mūsā b. ʿĪsā said to him, “My father resigned the office himself—what came of that?” Al-Maʾmun replied, “Your father was a man acting under coercion.” Al-Maʾmun went on promising and enticing ʿAbbās until the latter pledged allegiance to him as caliph. After returning to Baghdad, ʿAbbās continued to correspond with him, informing him of al-Amin’s doings and offering him advice.

When the envoys returned to al-Amin they related what his brother had said. Al-Faḍl b. al-Rabiʿ then pressed al-Amin all the more to depose al-Maʾmun; so al-Amin did so and ordered that prayers be said for his own son in every land. They appointed orators to speak against al-Maʾmun and enumerate his faults. They also sent to Mecca, retrieved the document that al-Rashīd had written and lodged in the Kaʿbah, and al-Amin tore it up. He then reaffirmed the oath of allegiance to his son al-Natiq bil-Haqq concerning the offices he had assigned him.

A series of letters and envoys passed between al-Amin and al-Maʾmun—too lengthy to recount here; Ibn Jarīr has recorded them in full in his History (2). Matters eventually reached the point where each man secured the territories and fortresses under his control, raised armies and troops, and sought the loyalty of the populace.

In this same year the Byzantines rose against their king Michael (3). They attempted to depose and kill him, so he abandoned the throne, embraced monasticism, and they installed Leo in his place.