By: Mir M.Hosseini
The fifth Abbasi Caliph Harunolrashid fell ill and died in Tus at the age of 46 and was buried in Mashhad. Harunolrashid's reign lasted for 23 years. With help from Iranian viziers, specially using teachings of Yahya Barmaki, he could give the Caliphate rule, the theme of an empire and turned Baghdad into a touristic place and a center for trade and knowledge.
The news of Harunolrashid's death soon reached Khorasan. In a secret meeting among nobles and elderly, Mamun his son from an Iranian mother was chosen as caliph. 3 weeks later, his brother Amin sent an army of 91,000 soldiers to counter Mamun's volunteer corps of 30,000 in Tehran. The Abbasi army leaded by Ali Bin Musa Bin Haman were defeated. The winning army proceeded to take Baghdad under siege. Soon Baghdad fell and Amin's head was sent to Mamun.