On Rhodes the Hospitallers, by then also referred to as the Knights of Rhodes, were forced to become a more militarized force, fighting especially with the Barbary pirates. They withstood two invasions in the 15th century, one by the Sultan of Egypt in 1444 and another by the Ottoman Sultan Mehmed the Conqueror in 1480 who, after capturing Constantinople and defeating the Byzantine Empire in 1453, made the Knights a priority target.