The reply of Mohammed was a prompt order to his {272} 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 {273} 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." The answer came loud and strong from every part of the camp. "Allah is great! There is no God but Allah, and Mohammed is His Prophet."