He held various posts in the late eighth and early ninth centuries, and played a supporting role in the events of the Fourth Fitna.
Al-Abbas was a grandson of Isa ibn Musa, the nephew of the first two Abbasid caliphs as-Saffah and al-Mansur and initial heir-apparent to the latter.
[4] In March 812 he participated in the failed coup of al-Husayn ibn Ali ibn Isa, in which he was responsible for personally apprehending both al-Amin and his mother Zubaydah bint Ja'far,[5] and he was subsequently selected to lead the first pilgrimages undertaken in al-Ma'mun's name, in 812, 813 and 814.
[6] In June 814 al-Abbas was appointed as governor of Egypt by al-Ma'mun, and he deputized his son Abdallah to take control of that province in his name.
[7] Al-Abbas then responded by setting out for Egypt in an effort to intervene, but in February 815 he suddenly died at Bilbays, allegedly due to poisoning.