John VI was succeeded to the throne by his brother, Constantine XI.
When Murad II died in 1451, his successor, Mohammed II the Conqueror (Mehmet II), was not distracted by other European ambitions from the great goal of Constantinople.
At once he set about his preparations for the grand attack on Constantinople.
As a last despairing effort to procure aid Constantine XI proclaimed the union of the eastern and western churches. The only effect though was the alienation of his own subjects. The Slavs were broken. Succession troubles paralyzed Hungary, the west was exhausted. From no quarter was aid forthcoming. Only the Venetians, Genoese and Catalans would help, for fear of Turkish dominance of the Mediterranean. And it was to these few allies that Constantine XI was compelled to entrust not merely maritime defence but the actual garrisoning of the city itself.
In 1452 Mohammed II completed his preparations unhindered. He laid much trust in the ability of modern artillery and employed a Hungarian gunfounder, called Urban, to cast him a siege artillery of seventy guns. Another major part of Mohammed II’s preparations was to contruct a fortress at the narrowest point of the Bosporus, called Rumeli Hisari, with which he could blockade the sea-straight.
In April 1453 the siege began. A Genoese squadron carrying supplies forced its way into the harbour, and two direct attacks were repulsed (May 6 and 12). But the small force could have little hope of maintaining resistance for very long.
No hint of help came.
By advice of his astrologers, Mohammed II waited for the fortunate day (May 29, 1453), when the grand assault was delivered on all sides simultaneously, by sea and by land.
The large cannons had already been used to batter down the magnicient walls in two places during the siege.
The small garrison, led by emperor Constantine XI personally, offered desperate resistance, but was alas overwhelmed.
Buried among the heaps of slain, the body of the last of the Roman emperors was never recovered. There was no general massacre, but the city was thoroughly sacked, its literary treasures dispersed or destroyed, and 60’000 of the population were sold into slavery.
Alas, the Eastern Roman Empire, too, had ceased to be.