Following the establishment of the Abbasid Caliphate, Caliph al-Mansur abolished the subsidies paid to the various Armenian princes (nakharar) and in addition imposed heavy tax duties on them. Coupled with instances of religious persecution against the majority Christian Armenian population, these measures prompted the outbreak of a major anti-Abbasid revolt in 774. The revolt was led by Artavazd Mamikonian, but gathered the direct or tacit support of most nakharar families, most notably the hitherto pro-Arab Bagratuni, while the Artsruni and Siwni families remained neutral. The rebellion spread through Armenia, including attacks against Arab tax-collectors, and the local Arab governor, al-Hasan ibn Qahtaba, was unable to contain it. The Caliph sent 30,000 Khurasanis under Amir ibn Isma'il