The historic age of India came to change with the invasion of the Greeks,
In HERODOTUS and CTESIAS ( Book VII. C65-70 )
It is mentioned that many Indians probably from the Punjab followed Xerxes to Greece.
They wore cotton dresses and carried bows of cane with iron tipped arrows.
" The Eastern Ethiopians , who came from Biluchistan, and were probably of a Cushite race, were marshalled with the Indians, and their equipment in most points resembled that of the Indians, but they wore on their heads scalps of horses with the ears and mane attached; the ears were made to stand upright, and the mane served as a crest. For shields they made use of the skins of cranes. The cavalry were dressed in like manner; they rode in chariots drawn by horses and wild asses."
In the Greek writers , reference is given to two Persian invasions of India.
First invasion: led by Cyrus and Second invasion led by Scylax .
"But it is only since the invasion of India by Alexander in the year 327 B.C that India is brought into a direct contact with the classic world. The relations then established lasted for several centuries, and we owe to them the full description of India found in the contemporary calssic authors.. From the accounts of Quintus Curtius ( I.27 Quintus Curtius speaks of armour made of iron lamine connected in rows within each other) we learn something of the character and condition of India armies at that period, how gallant was their defence, but how little able they were to oppose the superior tacties of the Greeks."
pg11 Illustrated Handbook of Indian Arms