Between 1346 and 1349 the Black Death killed almost half of the inhabitants of Constantinople. The city was further depopulated by the general economic and territorial decline of the empire. By 1450, the empire was exhausted and had shrunk to a few square kilometers outside the city of Constantinople itself, the Princes' Islands in the Sea of Marmara and the Peloponnese with its cultural center at Mystras. The Empire of Trebizond, an independent successor state that formed in the aftermath of the Fourth Crusade, was also present at the time on the coast of the Black Sea. By 1453, it consisted of a series of walled villages separated by vast fields encircled by the fifth-century Theodosian Walls.
When Mehmed II succeeded his father in 1451, he was just nineteen years old. Many European courts assumed that the young Ottoman ruler would not seriously challenge Christian hegemony in the Balkans and the Aegean. In fact, Europe celebrated Mehmed coming to the throne and hoped his inexperience would lead the Ottomans astray. This calculation was boosted by Mehmed's friendly overtures to the European envoys at his new court.