Answer
Mu'awiya ibn Abi Sufyan was assigned as the governor of Damascus by Umar ibn al-Khattab, the second caliph of the Rashidun Caliphate. Mu'awiya was a member of the Umayyad clan, and his appointment was seen as a way to ensure that the Umayyad family would have a strong presence in the region. Damascus was a strategically important city, and its control was essential for the stability of the caliphate.