He was besieged in Fustat, where Marwan was defeated and besieged there. Marwan's rivals for the caliphate, led by Abu al-Abbas al-Saffah, the first caliph of the Abbasid state. The Persians in the far east, Khurasan, followed him with the help of Abu Muslim al-Khurasani, who had been sent to them as a caller when he was only nineteen years old. He possessed a spirit and wisdom that only great men have, and he won the hearts of the people, making them all devoted. He fought Marwan's armies in Khurasan and defeated them, then advanced to Iraq and conquered it, and delivered the sermon there for Abu al-Abbas. As for Marwan, after the victory of his opponent, he marched to Mosul. Its people oppressed him, so he fled from the army and returned to Syria. He found it rebellious against him. He had no refuge but Egypt, as it was still, until that time, loyal to him. As for Abu al-Abbas, when he consolidated his power in Kufa, he appointed governors over the lands that came under his rule. He chose his governors from among the people of Sham and appointed them as rulers. He chose them for their seniority in the Abbasid state, which was established on the ruins of the Umayyad state. Then Abu al-Abbas, the caliph, decided to kill all the remnants of the Umayyad state and its callers, even if they had pledged allegiance to him. So he ordered their arrest. Eighty people, including women, men, and children, were ordered to be slaughtered together without mercy. He was thus nicknamed Al-Saffah that year. Only a young man named Abd al-Rahman, a grandson of Caliph Hisham, escaped this massacre. He fled to al-Andalus (Spain) and founded another Umayyad state there. As for Marwan, he was in Egypt, intending to keep it for himself. So he sent Abd Allah ibn Ali, his brother, to Abu al-Abbas. Abd al-Malik ibn Yazid and settled on Mount Yashkur, where Ibn Tulun had a great army. It was part of Fustat in its early days, then it became ruins. Abu Awn ordered his companions to build there, so they built and set up their camp there, calling it al-Askar. Its construction continued with the construction of Fustat. After that, the governor's house and a mosque were built, known as the Mosque of al-Askar, then known as the Mosque of the Coast. It became a city with great markets and houses, and the house of the rulers of Egypt, where they resided from the time of Abu Awn until Ahmad ibn Tulun built the districts and resided there. Then Sal ibn Ali began pursuing Marwan, and overtook him in the village of Busir in the Fayyum and killed him. He was transported in the year 132 AH, at the age of seventy. Others said in the year 132 AH. His head was sent to Abu al-Abbas al-Saffah. Marwan's caliphate lasted for five years and one month, and he was the last caliph of the Umayyad state in Sham.