Turkish expansion

Final Turkish assault

When Murad II became sultan, in 1421, the days of Constantinople and of Hellenism were numbered. In 1422 Murad revoked all the privileges accorded to the Byzantines by his father and laid siege to Constantinople. His armies invaded Greece and blockaded Thessalonica. The city was then a possession of Manuel II's son Andronicus, who in 1423 handed it over to the Venetians. For seven years Thessalonica was a Venetian colony, until, in March 1430, the Sultan assaulted and captured it. Meanwhile, Manuel II had died in 1425, leaving his son John VIII as emperor. John, who had already traveled to Venice and Hungary in search of help, was prepared to reopen negotiations for the union of the churches as a means of stirring the conscience of Western Christendom. His father had been skeptical about the benefits of such a policy, knowing that it would antagonize most of his own people and arouse the suspicion of the Turks. The proposal was made, however, at the Council of Florence in 1439, attended by the emperor John VIII, his patriarch, and many Orthodox bishops and dignitaries. After protracted and difficult discussions, they agreed to submit to the authority of Rome. The union of Florence was badly received by the citizens of Constantinople and by most of the Orthodox world. But it had its notable adherents, such as the bishops Bessarion of Nicaea and Isidore of Kiev, both of whom retired to Italy as cardinals of the Roman Church. Bessarion's learning and library helped to encourage further Western interest in Greek scholarship. The union of Florence also helped to stimulate a crusade against the Turks. Once again it was led by the king of Hungary, Wladyslaw III of Poland, supported by George Brankovic of Serbia and by János Hunyadi of Transylvania. But there were disagreements among its leaders, and the Christian army was annihilated at Varna in 1444.

The Byzantine collapse and the Ottoman triumph followed swiftly thereafter. In 1448 Constantine XI (or XII), the last emperor, left Mistra for Constantinople when his brother John VIII died without issue. His two other brothers, Thomas and Demetrius, continued to govern the Morea, the last surviving Byzantine province. In 1449 Mehmed II (sultan 1444 - 46 and 1451 - 81) began to prepare for the final assault on Constantinople. No further substantial help came from the West, and the formal celebration of the union of the churches in Hagia Sophia in 1452 was greeted with a storm of protest. Even in their extremity, the Byzantines would not buy their freedom at the expense of their Orthodox faith. They found the prospect of being ruled by the Turks less odious than that of being indebted to the Latins. When the crisis came, however, the Venetians in Constantinople, and a Genoese contingent commanded by Giovanni Giustiniani, wholeheartedly cooperated in the defense of the city. Mehmed II laid siege to the walls in April 1453. His ships were obstructed by a chain that the Byzantines had thrown across the mouth of the Golden Horn. The ships were therefore dragged overland to the harbour from the seaward side, bypassing the defenses. The Sultan's heavy artillery continually bombarded the land walls until, on May 29, some of his soldiers forced their way in. Giustiniani was mortally wounded. The emperor Constantine was last seen fighting on foot at one of the gates.

The Sultan allowed his victorious troops three days and nights of plunder before he took possession of his new capital. The Ottoman Empire had now superseded the Byzantine Empire; and some Greeks, like the contemporary historian Critobulus of Imbros, recognized the logic of the change by bestowing on the Sultan all the attributes of the emperor. The material structure of the empire, which had long been crumbling, was now under the management of the sultan-basileus. But the Orthodox faith was less susceptible to change. The Sultan acknowledged the fact that the church had proved to be the most enduring element in the Byzantine world, and he gave the Patriarch of Constantinople an unprecedented measure of temporal authority by making him answerable for all Christians living under Ottoman rule.

The last scattered pockets of Byzantine resistance were eliminated within a decade after 1453. Athens fell to the Turks in 1456 - 58, and in 1460 the two despots of Morea surrendered. Thomas fled to Italy, Demetrius to the Sultan's court. In 1461 Trebizond, capital of the last remnant of Greek empire, which had maintained its precarious independence by paying court to Turks and Mongols alike, finally succumbed; the transformation of the Byzantine world into the Ottoman world was at last complete.