As Sultan Mehmed II conquered Constantinople (today named Istanbul) in 1453, the state grew into a mighty empire, expanding deep into Europe, northern Africa and the Middle East. With most of the Balkans under Ottoman rule by the mid-16th century, Ottoman territory increased exponentially under Sultan Selim I, who assumed the Caliphate in 1517 as the Ottomans turned east and conquered western Arabia, Egypt, Mesopotamia and the Levant, among other territories. Within the next few decades, much of the North African coast (except Morocco) became part of the Ottoman realm.