 Complete the following phrase:  Starting in the 15th century the Ottoman Empire began to expand at the expense of the Byzantine Empire and other countries friendly to Genoese merchants. The gradual loss of Imperial territory, coupled with the destruction of smaller Christian states such as Trebizond, Cyprus, and Amasra chipped away at Genoese mercantile interests in the Black Sea. The Ottomans constructed a massive fleet, and in doing so became the domit naval power in the Eastern Mediterranean. In 1453 