The Arab city, the old or round city of Bagdad, was founded by the caliph Mansur of the Abbasid dynasty on the west side of the Tigris just north of the Isa canal in A.D.
Damascus was taken by the Carmathians, and the name of the Abbasid caliph substituted for that of Moizz in public worship. IJasan al-A~am advanced from Damascus through Palestine to Egypt, encountering little resistance on the way; and in the autumn of 971 Jauhar found himself besieged in his new city.
917," in Journal Royal Asiatic Society, 1895, 1897; Baghdad under the Abbasid Caliphate (1901).
Abu Moslim, the founder of the Abbasid dynasty, proclaimed himself his avenger, and on that occasion adopted the black garments, which remained the distinctive colour of the dynasty.
This adventurer now went into Media (Jabal), where a great number of maulas and Shiites, even members of the reigning dynasty and of the Abbasid family, such as the future caliph Mansur, rejoined him.