al-Amin’s army, and Ḥusayn declared the caliph deposed and secured the oath of allegiance for ʿAbd Allah al-Maʾmūn. That took place on Sunday, the eleventh of Rajab of that very year.
When Tuesday came, al-Amin was moved from his own palace to the palace of Abū Jaʿfar in the heart of Baghdad; he was strictly confined, fettered, and treated harshly. Al-ʿAbbās ibn ʿĪsā ibn Mūsā then ordered al-Amin’s mother, Zubaydah, to move there. She refused, so he struck her with a whip (1) and forced her to comply; she therefore relocated with her children.
At daybreak on Wednesday the people demanded their stipends from Ḥusayn ibn ʿAlī, and a dispute arose. The inhabitants of Baghdad split into two camps: one for al-Amin, the other against him. Fierce fighting followed; the caliph’s party prevailed, captured Ḥusayn ibn ʿAlī ibn ʿĪsā ibn Māhān, shackled him, and brought him before the caliph. His fetters were removed and he was seated upon the caliph’s own couch. Al-Amin then ordered that any commoner without a weapon be supplied with arms from the arsenals, whereupon the populace plundered the storehouses containing those weapons. Al-Amin next summoned Ḥusayn ibn ʿAlī ibn ʿĪsā, reproached him for his actions, and Ḥusayn replied that the caliph’s former clemency had emboldened him. The caliph pardoned him once more, bestowed a robe of honor upon him, made him vizier, handed him the signet ring, placed the affairs outside the caliphal private quarters under his charge, entrusted him with the war ministry, and dispatched him to Hulwān.
When he reached the bridge he fled with his entourage and servants. Al-Amin sent men after him; cavalry pursued, overtook, and engaged him. He fought back, but they killed him in mid-Rajab, brought his head to al-Amin, and the people renewed their pledge of allegiance to the caliph on Friday.
After Ḥusayn ibn ʿAlī ibn ʿĪsā was killed, the chamberlain al-Faḍl ibn al-Rabīʿ fled, while Ṭāhir ibn al-Ḥusayn seized most of the provinces on behalf of al-Maʾmūn, installing deputies over them. The majority of the regions deposed al-Amin and gave their allegiance to al-Maʾmūn. Ṭāhir advanced to al-Madāʾin, captured it together with Wāsiṭ and its districts, and, on al-Maʾmūn’s authority, appointed governors over the Ḥijāz, Yemen, Upper Mesopotamia, Mosul, and other areas; only a few lands still remained with al-Amin.
In Shaʿbān of that year al-Amin unfurled four hundred banners, each under its own commander, and sent them to fight Harthama ibn Aʿyan. They met in Ramadan, where Harthama routed them, captured their leader ʿAlī ibn Muḥammad ibn ʿĪsā ibn Nahīk, and sent him to al-Maʾmūn. Some of Ṭāhir’s soldiers deserted to al-Amin; he lavished great sums upon them, honored them, and stained their beards with ghāliyah (2), so they became known as “the Army of the Ghāliyah.” Al-Amin then mustered them, sending a large force with them against Ṭāhir, but Ṭāhir routed them, scattered their ranks, and seized their possessions. He then drew near to Baghdad and besieged it, dispatching emissaries and spies to sow sedition among the troops until they split into factions. A clash (3) then broke out within the army, and the turmoil (4)