 In 679, a thirty-year peace treaty was concluded, obliging the Umayyads to pay an annual tribute of 3,000 gold coins, 50 horses and 50 slaves, and withdraw their troops from the forward bases they had occupied on the Byzantine coast.The outbreak of the Muslim civil war allowed the Byzantine emperor Constantine IV () to extort territorial concessions and enormous tribute from the Umayyads.In 685, the emperor led his army to Mopsuestia in Cilicia, and prepared to cross the border into Syria, where the Mardaites, an indigenous Christian group, were already causing considerable trouble.