This piece of history will be completely edited later
Though Mansour, the second Abbasid Caliph (born in 712 and died 775 AD) had killed Abu Muslem Khorasani, and many other Iranian patriots and sent an army to Khorasan to beat Almughanna (Hashem Bin Hakim), announced on 14 December 770 AD that Nowrooz and Mehregan would be celebrated in his court in Baghdad (which he had turned into a city) in the same manner as celebrated by the Sassanid kings.
From the very beginning the Abbasid Caliphs had used Iranians for administration and counseling, which reached its highest level during the rule of Haroon Al Rashid and his son Ma’mun, and in fact, the Iranians were running the vast Abbasid Empire.
Mansour, who had won over Ma’mun with the help of Abu Muslem Khorasani and drove them out (in the East Mediterranean) became Caliph in the year 745 AD. In spite of all the help that Mansour received from Abu Muslem he killed him in 775 AD and with this action provoked the anger of the Iranians. Almughanna, who was once an officer in the army of Abu Muslem, together with his followers, intensified the war with the Caliphet court but was defeated in the war with the dispatched army of the Caliph and committed suicide.
In the beginning of their rule, The Abbasid Caliphs faced uprising of Iranians, like Sindbad Nayshabouri, Behafarid, Astazesees and . . . and could not bring peace to Khorasan, Sistan and Rey, and since these rebels were pro-Iranian, the then Caliph chose to follow Iranian customs in order to reduce the rate of hostilities and gain the people’s consent. Before the Abbasid’s, Hashem Bin Abdul Malik, the Umavid ruler of Damascus, had also yielded to Iranian customs.
Translation by Rowshan Lohrasbpour (AmordadNews writer)