The Persians, however, were not yet done with. By 321 B.C., two years after his defeat at Issus, Darius had collected an army greater than ever before, and Alexander, coming eastward out of Egypt, met this vast host, said to have been a million strong, at Gaugemela, or Arbela, and in this third and last conflict his victory was decisive. Darius fled eastward, with Alexander constantly in pursuit of him. Alexander took the great cities of Babylon and Susa on his way. The fugitive Darius was assassinated in Parthia, and Alexander's lordship over the ancient empire was complete. Yet that was not enough for him. He pushed forward into India, across high mountain ranges and wide rivers. What he accomplished there, in the way of conquest, was marvellous, yet it had no big effect on the great story, because his conquests beyond the mountains were not lasting. His wonderful troops, though they must have looked on him as almost supernatural in his ability to lead them on to victory, began to long for their homes, probably to wonder if they would ever see them again after coming so far. He reached the shores of the Indian Ocean, and thence set his face to return homeward. In Babylonia he stayed awhile, arranging for the government of the immense empire of which he was the undisputed master, and there he died, of a fever which is said to have been brought on, or greatly increased, by intemperate drinking--a death unworthy of his extraordinary achievements and of a pupil of such a master as Aristotle. {159} And death at thirty-two! The exploits of Alexander and his army are unequalled in the whole course of the story of the world. Yet we must ever remember how much of that immense achievement was due to the genius of his father Philip, who created all the fighting force which the son led so triumphantly. The fame of the son is so glorious that the father's work is rather hidden by it. What Philip might have done, if he had lived, with the great machine of war which he devised we cannot tell, but it is sure that Alexander could not have achieved his conquests as he did but for the machinery which his father had made ready for him. [Sidenote: Death of Alexander]