The Roman Exarchate of Africa was not able to withstand the seventh-century Muslim conquest of the Maghreb. The Umayyad Caliphate under Abd al-Malik ibn Marwan in 686 sent a force led by Zuhayr ibn Qays, who won a battle over the Romans and Berbers led by King Kusaila of the Kingdom of Altava on the plain of Kairouan, but he could not follow that up. In 695, Hassan ibn al-Nu'man captured Carthage and advanced into the Atlas Mountains. An imperial fleet arrived and retook Carthage, but in 698, Hasan ibn al-Nu'man returned and defeated Emperor Tiberios III at the 698 Battle of Carthage. Roman imperial forces withdrew from all of Africa except Ceuta. Fearing that the Byzantine Empire might reconquer it, they decided to destroy Roman Carthage in a scorched earth policy and establish their headquarters somewhere else. Its walls were torn down, the water supply from its aqueducts cut off, the agricultural land was ravaged and its harbors made unusable.