When the Muslim army conquered the town of Ein-Ul-Tamr they found a number of Arab Christian priests in a monastery. One of them was called Nusair another called Serine. They both embraced Islam, Nusair is the father of Mosa Ben Nusair, the supreme commander of the forces which later conquered Spain under the leadership of Tariq Ben Zeyad, the second in command for Mosa Ben Nusair. Serine, the other convert, is the father of the scholar Ibn Serine who became one of the more celebrated Muslim theologians. Muslim conquest of the Persian Empire Campaigns of Khalid ibn al-Walid. This battle took place in modern day Iraq between the early Muslim Arab forces and the Sassanians along with their Arab Christian auxiliary forces. Ein-ul-tamr is located west of Anbar and was a frontier post which had been established to aid the Sassanids. The Muslims under Khalid ibn al-Walid's command soundly defeated the Sassanian auxiliary force, which included large numbers of non-Muslim Arabs who brokeearlier covenants with the Muslims. According to non-Muslim sources, Khalid ibn al-Walid captured the Arab Christian commander, Aqqa ibn Qays ibn Bashir, with his own hands