Meantime the doomed city of Constantinople had been further weakened by internal strife. Hoping to get aid from the Pope, John Palæologus, the Emperor, had publicly conformed to the Roman Church, with many of his followers. But the bulk of the inhabitants of Constantinople utterly refused to throw over the ancient faith of the Greek Church, and preferred to disown their Emperor. As one of them ominously muttered: "Better the turban of the Turk in Constantinople than the Pope's tiara."

Disappointed of his hopes of any practical aid from Rome, John worked on in terrified silence while the brave King of Poland and Hungary tried in vain to drive back the triumphant Turks. He died only three years before the dreaded Amurath, and was succeeded by his brother Constantine, bearer of the honoured name of the founder of the city, but destined to be the last Christian ruler of the Eastern Empire.

Before very long, Constantine found himself face to face with the young Mohammed, the son of Amurath, who was already surnamed the Conqueror.

The all-absorbing desire of Mohammed was the possession of Constantinople, in order that it might be made the capital of his own Empire. Some pretence therefore must be found for a rupture with his meek vassal Constantine. At that time there dwelt within the city a certain Ottoman prince named Orkhan, much given to plots and ambitions, on whose account the Emperor was paid a considerable sum by Mohammed, on condition that he was kept from doing any harm. Very unwisely Constantine sent envoys to press for a larger payment, and even went so far as to try to blackmail the Sultan by hinting that Orkhan had the better right to the throne.

The reply of Mohammed was a prompt order to his engineers to construct a series of forts between Constantinople and the Black Sea, and thus to begin the siege by isolating the city from her port and food supplies. The actual excuse for warfare was provided in an attack made by some Greek soldiers on the Turks who were pulling down a beautiful old church in order to use its stones for their fort. The Greeks were promptly cut to pieces, and when Constantine dared to remonstrate, Mohammed at once declared war.

In vain did the despairing Emperor seek for help from the West. Even Genoa and Venice were blind to the approaching loss of all their Eastern trade, and Rome could do little to help. When the Emperor made a strong appeal to his own subjects to rally to the protection of their city, they listened in sullen silence to the words of one who had renounced the faith of his ancestors and conformed to the Church of Rome. There was never the smallest chance of holding out against the vigorous young Sultan and his picked troops.

In the spring of 1453 the actual siege began. Mohammed made use of that gunpowder which was to revolutionise all the ancient modes of warfare, and the old walls of Constantinople shuddered and fell before the shock.

The besieged had their guns too, but they did more harm than good, for the walls were too narrow to hold them and were so shaken by the concussion that these weapons had to be abandoned.

Yet for a time, owing largely to the courage and spirit of Constantine, the city not only held out, but succeeded in sending five vessels into the midst of the Turkish fleet, sinking and otherwise destroying all with which they came into contact. For allowing this to happen, the Turkish admiral, in spite of his plea of an injured eye as the cause of the mishap, was sentenced to receive a hundred strokes from a golden rod in the presence of the angry Sultan.

But this victory was quickly counterbalanced by Mohammed, who had some of his vessels brought overland across the neck that lies between the Bosphorus and the Golden Horn, thus shutting out the city from the sea on both sides. After a siege of forty days the end came on May 29, 1453. A special effort was urged by the Sultan in these words: "The city and the buildings are mine, but I resign to you the captives and the spoil, the treasures of gold and beauty; be rich and happy. Many are the provinces of my Empire; the intrepid soldier who first ascends the walls of Constantinople shall be rewarded with the government of the fairest and most wealthy; and my gratitude shall accumulate his honours and fortunes above the measure of his own hopes."