The Arab fleet had continually harassed the Byzantine navy for five years, starting in 672. In 677 they launched raids along the coast of Anatolia, into the Sea of Marmara, and besieged Constantinople itself, while at the same time an army raided Anatolia. Coincidentally the Slavs were attacking Thessalonica by land, so that the Byzantine army was distracted on two fronts. Byzantine emperor Constantine IV sent his fleet to meet the Arabs near Syllaeum, and the Arab fleet was destroyed by Greek fire, a new Byzantine weapon that had been used for the first time only a few years before. As the Arabs retreated they were caught in a storm that sank nearly all of their ships. Meanwhile, the Byzantine army pursued the Arabs back to Syria and defeated them there. This ended the immediate Arab threat to eastern Europe, and peace lasted for almost 30 years.