the complete subjugation of Byzantium as their ultimate objective. Their thinking was dominated by Islamic teaching, which placed the infidel Byzantines in the Dār al-Ḥarb, the "House of War", which, in the words of Islamic scholar Hugh N. Kennedy, "the Muslims should attack whenever possible; rather than peace interrupted by occasional conflict, the normal pattern was seen to be conflict interrupted by occasional, temporary truce (hudna). True peace (ṣulḥ) could only come when the enemy accepted Islam or tributary status." Both as governor of Syria and later as caliph, Muawiyah I (r. 661–680) was the driving force of the Muslim effort against Byzantium, especially by his creation of a fleet, which challenged the Byzantine navy and raided the Byzantine islands and coasts. To stop the Byzantine harassment from the sea during the Arab-Byzantine Wars, in 649 Muawiyah set up a navy, manned by Monophysitise Christian, Copt and Jacobite Syrian Christian sailors and Muslim troops. This resulted in the defeat of the Byzantine navy at the Battle of the Masts in 655, opening up the Mediterranean. The shocking defeat of the imperial fleet by the young Muslim navy at the Battle of the Masts in 655 was of critical importance: it opened up the Mediterranean, hitherto a "Roman lake", to Arab expansion, and began a centuries-long series of naval conflicts over the control of the Mediterranean waterways. 500 Byzantine ships were destroyed in the battle, and Emperor Constans II was almost killed. Under the instructions of the caliph Uthman ibn Affan, Muawiyah then prepared for the siege of Constantinople. Trade between the Muslim eastern and southern shores and the Christian northern shores almost ceased during this period, isolating Western Europe from developments in the Muslim world: "In antiquity, and again in the high Middle Ages, the voyage from Italy to Alexandria was commonplace; in early Islamic times the two countries were so remote that even the most basic information was unknown" (Kennedy). Muawiyah also initiated the first large-scale raids into Anatolia from 641 on. These expeditions, aiming both at plunder and at weakening and keeping the Byzantines at bay, as well as the corresponding retaliatory Byzantine raids, eventually became established as a fixture of Byzantine–Arab warfare for the next three centuries. The outbreak of the Muslim Civil War in 656 bought a precious breathing pause for Byzantium, which Emperor Constans II (r. 641–668) used to shore up his defences, extend and