Abu Ja'far Al-Mansur was born at the home of the 'Abbasid family after their emigration from the Hejaz in 95 AH (714 AD). "His father, Muhammad, was reputedly a great-grandson of Abbas ibn Abd al-Muttalib, the youngest uncle of Mohammad; his mother was a Berber woman.". He reigned from Dhu al-Hijjah 136 AH until Dhu al-Hijjah 158 AH (754 AD--775 AD). In 762 he founded as new imperial residence and palace city Madinat as-Salam, which became the core of the Imperial capital Baghdad. Al-Mansur was concerned with the solidity of his regime after the death of his brother, Abu'l `Abbas, who later become known as-Saffah (the bloodshedder). In 755 he arranged the assassination of Abu Muslim. Abu Muslim was a loyal freed man from the eastern Iranian province of Khorasan who had led the Abbasid forces to victory over the Umayyads during the Third Islamic Civil War in 749-750. At the time of al-Mansur he was the subordinate, but undisputed ruler of Iran and Transoxiana. The assassination seems to have been made to preclude a power struggle in the empire.