Before the attack was made that seemed certain to prove fatal to the last stronghold, the capital of the Christian Empire, Bayezid was called away to meet the onslaught of the greatest of conquerors, Timur the Tartar. The great battle of Angora shattered the Turkish power, destroyed the Janissaries and left Bayezid himself a prisoner in the hands of Timur. Before a year was over, the proud Sultan died, and the power which he had made so great was utterly crushed beneath the feet of the Tartars. Brusa itself was left in ruins, and not only the son of Bayezid, who was safe in Adrianople, made submission, but even the Emperor paid tribute to Timur. Then the conquering horde swept back again to the Far East, and the Turks set to work to rebuild again the power that had been shattered. Domestic warfare succeeded the destruction at the hands of foreign foes, and Mohammed I., the youngest son of Bayezid, established his authority over his brothers as ruler of the Osmanlis by the aid of the Emperor Manuel Palæologus. His brother Musa laid siege to Constantinople, and the troops of Mohammed actually joined with those of Manuel in the successful defence of the city. Mohammed was the ally, almost the subject, of the Emperor, and when he died he sought to commend his children to Manuel's care. Mohammed died in 1421 at Adrianople. His son Murad II. had to fight for his throne against a pretender whom the Emperor had set free, and whom he overcame only by the help of the Genoese galleys which carried him from Asia to Europe. In 1422 he was ready to revenge himself on the Greeks. His army encamped before the walls of Constantinople, and his own tent was set up in the garden of the Church of the Blessed Virgin of the Fountain (Balukli). He brought his cannon to bear upon the walls that cross the valley of the Lycus, but without success. The walls of Theodosius were still too strong, and the fierce attack on the gate of S. Romanus was a failure now, as it would not be thirty years later. The city was stoutly defended. John Palæologus, the Emperor's son, commanded a garrison inspired by the fullest religious enthusiasm: and when a vision of the Blessed Virgin, the Panhagia, was seen on the walls, both by assailants and defenders, the siege was given up; and the Sultan did not attempt to renew it. Still, a tribute was paid by the Emperor, and it must have been clear to the Osmanlis that the capture was but for a short time deferred. But Murad had to undergo defeats at the hands of the Hungarians, which he amply avenged: and his two abdications showed that he was weary of power, if not incapable of wielding it. The end of his reign saw him repeatedly over-matched by the Albanian hero, Scanderbeg, whom he himself had trained among the Janissaries. In 1451 he died; and then the greatest triumph of the Osmanlis was at hand. The early history of Mohammed II. has been thus summed up, in the clear-cut eloquence of Dean Church.