The campaign faced difficulties already in its early stages, when the news arrived of the accession of a new caliph, Hisham ibn Abd al-Malik, and the appointment of a new governor of Iraq, Khalid al-Qasri. This brought the long-simmering tribal rivalries of the Arabs of Khurasan to the fore: the Yemeni (southern Arab) troops in Balkh initially refused to join the campaign, as they expected the imminent recall of al-Kilabi (who was of northern Arab stock) by the new regime.[7] Only after Nasr ibn Sayyar led a force of Mudaris (northern Arabs) against them and defeated them at Baruqan did the Yemenis join al-Kilabi's army. The campaign eventually went ahead as Khalid al-Qasri wrote to al-Kilabi, urging him to proceed with it until his replacement, Khalid's brother Asad, arrived in Khurasan.