however, during the reign of the caliph al-mahdi (775-85) the afshin of oshrusana is mentioned among several iranian and turkic rulers of transoxania and the central asian steppes who submitted nominally to him. but it was not until harun al-rashid's reign in 794-95 that fadl ibn yahya of the barmakids led an expedition into transoxania and received the submission of the ruling akin, this kharākana had never previously humbled himself before any other potentate. further expeditions were nevertheless sent to oshrusana by ma'mūn when he was governor in marv and after he had become caliph. afshin kavus, son of the afshin karākana who had submitted to fadl ibn yahya, withdrew his allegiance from the arabs; but shortly after ma'mun arrived in baghdad from the east (817-18 or 819-20), a power struggle and dissensions broke out among the reigning family of oshrusana.