Then yet another member of the Prophet’s Household rose in rebellion.

When the month of Ramadan of that same year arrived, al-Hasan ibn Zayd ibn Muhammad ibn Ismaʿil ibn al-Hasan ibn Zayd ibn al-Husayn ibn ʿAli ibn Abi Talib appeared in the region of Ṭabaristan. The reason was that, after Yaḥyā ibn ʿUmar had been killed, the caliph al-Mustaʿin granted Muḥammad ibn ʿAbd Allah ibn Ṭāhir a tract of land in that area. Muḥammad sent his secretary—a Christian named Jābir ibn Hārūn—to take possession of the estates. When he arrived, the local people were greatly displeased. They sent for al-Hasan ibn Zayd, who came to them, whereupon they offered him their allegiance. The Daylamites and a number of regional amirs rallied to him; he mounted with his supporters, entered Āmul in Ṭabaristan, seized it by force, and collected its revenue. His power grew markedly.

He then moved out to fight Sulaymān ibn ʿAbd Allah, the governor of those districts. Several battles ensued until Sulaymān suffered a crushing defeat, abandoning his family and wealth and retreating no closer than Jurjān. Al-Hasan ibn Zayd entered “Sāriyah” (1), took the money and stores it contained, and sent Sulaymān’s household to him by boat, honourably treated. Thus the entire governorship of Ṭabaristan fell under al-Hasan ibn Zayd’s control.

Next he marched on Rayy, captured it as well, expelled the Ṭāhirids, and extended his authority to the garrison of Hamadhān.

When news of these events reached al-Mustaʿin—whose realm was then being administered by Wāṣif the Turk—the caliph was deeply distressed and exerted himself in dispatching armies and reinforcements to fight this al-Hasan ibn Zayd (2).

On the Day of ʿArafah of the same year, Ahmad ibn ʿĪsā ibn Ḥusayn al-Ṣaghīr ibn ʿAlī ibn al-Ḥusayn ibn ʿAlī ibn Abi Talib, together with Idrīs ibn Mūsā ibn ʿAbd Allah ibn Mūsā ibn ʿAbd Allah ibn Ḥasan ibn Ḥasan ibn ʿAlī ibn Abi Talib, appeared in Rayy. Ahmad ibn ʿĪsā led the people in the ʿId prayer that year and called them to the riḍā (the divinely approved leader) from the family of Muhammad. Muḥammad ibn ʿAlī ibn Ṭāhir fought him, but Ahmad ibn ʿĪsā defeated him, and his influence became formidable (3).

In this year as well the people of Ḥimṣ rebelled against their governor al-Faḍl ibn Qārīn [brother of al-Māzyār ibn Qārīn] (4), killing him in Rajab. Al-Mustaʿin thereupon sent against them Mūsā ibn Bugha the Elder. They fought at al-Rastan; he routed them, killed many of the townspeople, burned a number of their quarters, and took the leading men captive (5).