In the 680s, Justinian II (685–695 and 705–711) paid attention to the needs of the navy, strengthening it by the resettlement of over 18,500 Mardaites along the southern coasts of the Empire, where they were employed as marines and rowers. Nevertheless, the Arab naval threat intensified as they gradually took control of North Africa in the 680s and 690s. The last Byzantine stronghold, Carthage, fell in 698, although a Byzantine naval expedition managed to briefly retake it. The Arab governor Musa bin Nusair built a new city and naval base at Tunis, and 1,000 Coptic shipwrights were brought to construct a new fleet, which would challenge Byzantine control of the western Mediterranean. Thus, from the early 8th century on, Muslim raids unfolded unceasingly against Byzantine holdings in the Western Mediterranean, especially Sicily. In addition, the new fleet would allow the Muslims to complete their conquest of the Maghreb and to successfully invade and capture most of the Visigoth-controlled Iberian Peninsula.