In 647, a Rashidun-Arab army led by Abdallah ibn al-Sa’ad invaded the Byzantine Exarchate of Africa. Tripolitania was conquered, followed by Sufetula, 150 miles (240 km) south of Carthage, and the governor and self-proclaimed Emperor of Africa Gregory was killed. Abdallah's booty-laden force returned to Egypt in 648 after Gregory's successor, Gennadius, promised them an annual tribute of some 300,000 nomismata.