At this stage, and before he could give effect to his threats, Bayezid was compelled by great events in Asia to raise the siege of Constantinople. Hitherto, in twelve years of incessant war, Bayezid had been uniformly successful. He had annexed the greater part of Asia Minor, Macedonia, Northern Bulgaria, and Thessaly. He had reduced to vassalage the Greek Empire itself and Serbia, Wallachia, Bosnia, and a great part of Greece. He had defeated the feudal chivalry of Europe in the great battle of Nicopolis. He had not met with a single reverse. The next two years, the last of his reign, were to result in disastrous and overwhelming defeat to him, in his capture and death, and in the temporary crumpling up of the Turkish Empire. He came into conflict for the first time with Timur, a general and a conqueror more resolute, crafty, able, and cruel than himself. Timur the Tartar, better known to us as Timurlane—Timur the lame, for he had met in early life with an accident which lamed him—was the greatest, the most ruthless, and the most devastating of warriors recorded in all history. Born in 1333, a descendant through his mother of the great Gengis Khan, he began life as a petty chief of a Tartar tribe in the neighbourhood of Samarkand. It was not till he had reached the age of thirty-five that he achieved eminence over other neighbouring Tartar States. He then conceived the ambition of universal conquest. “As there was only one God in heaven,” he said, “so there should be only one ruler on earth”—that one was to be himself. He went a long way towards gaining this object of his ambition, for he embarked on a career which, in rather less than thirty-five years, resulted in an empire extending from the Great Wall of China to the frontier of Asia Minor, and from the Sea of Aral to the River Ganges and the Persian Gulf. He had, by this time, conquered twenty-seven separate States and extinguished nine dynasties. He effected his purpose, not only by force of arms, but by a deliberate policy of terrorism. After victory he was of settled purpose ruthless in cruelties on the greatest scale. It was obvious that, sooner or later, he would come into conflict with what was, at that time, the only other growing military Power in the world—the Ottoman Empire. The two potentates had already become neighbours, and causes of dispute and antagonism were often arising between them. Each had sheltered refugee princes, whose territories had been absorbed by the other, and who were engaged in intrigues to stir up war between the two rivals, in the hope of regaining their possessions. Insolent messages passed between the two potentates.