Writing of the city of Nysa, Arrian says that "it was built by Dionysos or Bacchus, when he conquered the Indians; but who this Bacchus was, or at what time or from whence he conquered the Indians is hard to determine, whether he was that Theban who from Thebes, or he who from Timolus, a mountain of Lydia, undertook that famous expedition into India is very uncertain." There is a Greek epic poem in hexameter verse, called the "Dionysiaka," or "Bassarika," which tells of the conquest of India by Bacchus, the greatest of all his achievements. The author is Nonnus of Panopolis in Egypt, who wrote about the beginning of the fifth century of our era. Bacchus is said to have received a command from Zeus to turn back the Indians, who had extended their conquests to the Mediterranean, and in the execution of this command he marched through Syria and Assyria. In Assyria he was entertained with magnificent hospitality. Nothing further is said of the route he took to reach India. The first battle which took place in India was on the banks of the Hydaspes, where the Indians were routed. Then followed as an incident in the war the destruction of the Indian fleet in a naval battle, which is instructive. It took the assistance of the goddess of war, Pallas Athene, to bring the campaign to a conclusion, which terminated with the death of the Indian leader Deriades. Here, then, is crystallized in verse the tradition to which Arrian refers, and remembering that we are indebted to two great epics of India, the "Ramayana" and the "Mahabharata," for such glimmering of the ancient history of the Aryan occupation of India as we possess, we may very well conceive that the germs of real historical fact lie half-concealed in this poem of Nonnus. However that may be, it is tolerably certain that Alexander found a people in Northern India who claimed a Greek origin when he arrived there, quite apart from the colonists of Baktria who had been transported there by Darius Hydaspes, and that he recognized their claim to distant relationship.
When Alexander, then, mustered his army in the sunny fields of Macedon he was preparing for an expedition over no uncertain ways between Greece and Baktria or Arachosia (Northern and Western Afghanistan). He knew what lay before him if he could once break through the Persian barrier; and the strength of that barrier he must have been well aware lay as much in the stern fighting qualities of the mercenary Greek legions in the pay of Persia as in the hosts of Persian and Indian troops which the Persian monarch could array against him. We have lists of the component forces on both sides. The Macedonian legions were homogeneous and patriotic. The Persian army was partly European, but chiefly Asiatic, with a mixed company of Asiatic troops such as has probably never taken the field since. The opposing forces, indeed, partook of the nature of the two armies which fought out the issue of the Russo-Japanese campaign, and the result was much the same. There was no tie of national sentiment to bind together the unwieldy cohorts of Persia. They fought for their pay, and they fought well; but when big battalions are divided in religious sentiment and unswayed by patriotism, they are no match for Macedonian cohesion, Mahomedan Jehad, or Japanese Bushido.