He was one of the last prominent members of the Banu Sulaym tribe to convert to Islam, and fought against Muhammad at the Battle of Hunayn in 630. After becoming a Muslim, he took part in the conquest of Syria in the 630s and fought at Yarmouk. Later, he commanded the Arab navy during the campaigns against the Byzantines in the eastern Mediterranean, including the decisive Muslim victory at the Battle of the Masts in 654. His army was also responsible for the destruction of the colossus of Rhodes. From the First Muslim Civil War until his disappearance from the historical record in the 660s, Abu al-A'war served Mu'awiya in a number of capacities, including as a commander and negotiator at the Battle of Siffin, an operative of Amr ibn al-As in Egypt, a tax administrator in Palestine and the governor of Jordan; he had held the latter post since the reign of Uthman.