They showed much improvement in the siege-methods employed, for they used wooden towers, and tried to get into the city through the aqueduct. The Greek armies were beaten in front of the walls, but Manuel and his son, John, soon found a way for causing the withdrawal of Murad’s army, by inviting over from Asia another son of Mohammed, to whom his brother had intrusted the government of one of the Asiatic provinces. He was ceremoniously received in the city, and as soon as it was known in the Turkish camp that he was on his way to the west, Murad withdrew to Adrianople. This siege is signalized in the chronicles by a narrative of the miraculous appearance of the Virgin on the walls of the city, the very day a general assault had been ordered. The Ottomans, panic-stricken, it is said, hastened to retreat. Both Christians and Mohammedans accepted the authenticity of the apparition, which is not surprising, since, in the ranks of the Sultan’s army, there were large numbers of men who had been converted to Islam, but who could not throw aside the religious habits of mind of medieval Christians. Peace was made on conditions extremely favorable to the Greeks. There was still a tribute to be paid, but some territory that had been taken in the campaign was restored. When Manuel died in 1425 he left six sons, all of whom were in positions of command. One of them, John VIII, was his successor as Emperor, the others were ruling parts of the empire at Thessalonika and farther south. One of the first acts of the new administration was to endeavor to placate the Turks by restoring some of the towns on the Black Sea. But the efforts at pacification were of no avail. The Morea was invaded by one of the Sultan’s generals, Tourakhan-beg, whose progress was not effectively contested, except by the Albanian colonies. The inhabitants of these were, however, mercilessly slaughtered, and on the site of the razed towns the Turks erected pyramids of the heads of their victims. In the north, too, there was successful fighting on the part of the Ottomans, both with the Roumanians and the Bulgarians, and even with the Hungarians, whose King, Sigismund, was defeated near the walls of Kolunbitz.