The next step was to the threshold of Constantinople itself, but for this the Turkish chieftain Murad was content to wait awhile. The capital was bound to fall in time, and he was first of all eager to make sure of his ground in Asia Minor. During Murad's reign he extended his domain to the Balkans and up to the very walls of the imperial city; whilst the unhappy Emperor without an empire was thankful to escape for the present by acknowledging his supremacy, and even by taking up arms at his command against one of his own free towns. For the next hundred and fifty years the Ottomans were only hindered from the invasion of Christendom by the determined action of the Servians and Hungarians. And meantime the chance of freeing the Greek Empire altogether from Ottoman rule had come and gone. In 1402, when the Turkish Sultan Bajazet was pressing hard upon Constantinople, the great Tamerlane, chief {269} of the Tartar hordes, who had already conquered Persia, Turkestan, Russia, and India, came down like a thunderbolt upon the ambitious plans of Bajazet. The latter defied the conqueror, saying, "Thy armies are innumerable? Be they so! But what are the arrows of the flying Tartar against the scimitars and battle-axes of my firm and invincible Janissaries?" Alike in their religious faith and in their ambitions, these two men now became deadly rivals; but not even the "New Army" of the Ottoman could stand against the Tartar hordes. One city after another fell and was sacked; Bajazet himself was taken, and imprisoned, according to one story, in an iron cage. Another and more modern version says that the great Tamerlane treated his captive with the utmost courtesy and consideration; and on the occasion of the victorious feast after the battle, placed a crown upon his head and a sceptre in his hand, promising that he should return to the throne of his fathers with greater glory than before. But Bajazet died before his generous conqueror could carry out his promises, and Tamerlane, taking his place, demanded tribute of his sons and of Manuel of Constantinople at the same time. The two elder sons of Bajazet were now at variance over the poor remains of his empire. One of these bought the aid of Manuel by surrendering the coast of Thessaly and the seaports of the Black Sea, and the Emperor was able to keep these just so long as the war between the brothers continued to rage. Even after this had ended in the triumph over both of Mohammed, Bajazet's youngest son, Manuel could feel fairly safe, for of late years he had thrown in his {270} lot with Mohammed and was allowed to hold his possessions in peace. This period of civil war, was of course, the opportunity for the Greek ruler to have driven out the Ottomans from his former empire. But this opportunity was lost as so many others had been, and after Mohammed died in 1421, the empire was entirely surrendered to the Ottomans.