According to the Orientalist Karl Vilhelm Zetterstéen, al-Mu'tadid "had inherited his father's gifts as a ruler and was distinguished alike for his economy and his military ability", becoming "one of the greatest of the Abbasids in spite of his strictness and cruelty".
His brothers Muhammad and Ibrahim had been killed by the Abbasids during an abortive rebellion, and Idris himself escaped after the defeat of another Alid uprising at the Battle of Fakhkh in 786 and took refuge in the western Maghreb (nowadays Morocco).
After the Fatimids conquered the district from the Abbasids, Jerusalem eventually became the capital, and the principal towns were Ashkelon, Ramla, Gaza, Arsuf, Caesarea, Jaffa, Jericho, Nablus, Bayt Jibrin, and Amman.
He contacted Abbasids and claimed he is ready to battle Babak Khurramdin in return for his rule over Armenia and Azarbaijan.
By the time of Ya'qub's death, he had conquered the Kabul Valley, Sindh, Tocharistan, Makran (Balochistan), Kerman, Fars, Khorasan, and nearly reached Baghdad but then suffered a defeat by the Abbasids.