Isa ibn Musa

ʿĪsā ibn Mūsā ibn Muḥammad ibn ʿAlī ibn ʿAbdallāh ibn al-ʿAbbās (ca. 721–783/4) was a nephew of the first two Abbassid Caliphs, as-Saffah (r. 750–754) and al-Mansur (r. 754–775), and for a long time heir-apparent of the Caliphate, until he was superseded by al-Mansur's son al-Mahdi (r. 775–785).

Isa ibn Musa was born in AH 103 (721/2 CE). In summer 750, immediately after the end of the Abbasid Revolution, Isa was appointed by his uncle as-Saffah as governor of Kufa, the first seat of the Abbasid government. He would retain the post for fifteen years—according to Hugh N. Kennedy, the second longest tenure in the Abbasid period after that of Dawud ibn Yazid al-Muhallabi in the early 9th century.

In 754, as as-Saffah was nearing his death, and as his designated heir Abu Ja'far (al-Mansur) was on pilgrimage in Mecca at the time, the Caliph appointed Isa, then about 34 years old, as the second heir, in the event anything should happen to al-Mansur. This move was necessary to prevent Abu Muslim, the powerful and popular general who had begun the Abbasid Revolution in Khurasan, from rising to the position of king-maker. Isa had already proven his ability as governor, and his proximity to the capital, al-Anbar, was crucial for a swift succession. When as-Saffah finally died, Isa proclaimed al-Mansur Abu Ja'far as Caliph and sent riders to notify him of his accession. According to the sources recorded by al-Tabari, Isa placed guards before the treasuries and government offices in the capital, until the new caliph arrived there. He also sent as-Saffah's chamberlain, Abu Ghassan, to inform Abdallah ibn Ali in Syria of as-Saffah's death and receive the oath of allegiance (bay'ah) from him.

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