Alexandra the invasion
In a letter to his mother, Alexander described his encounters with these trans-Indus tribes thus:
"I am involved in the land of a leonine and brave people, where every foot of the ground is like a well of steel, confronting my soldier. You have brought only one son into the world, but everyone in this land can be called an Alexander”.
His journey followed ...
Crossed the Jhelum : advantage of attack on the forces of Porus via the wooded island
The attack on the Gangartic Kingdom of Magadha beyond the Sutlej. Alexandras troops refused to cross the Sutlej and after His death no further accounts were made untill his successor Selecus crossed the Indus and defeated Sandracottus
(Chandra Gupta) and the whole of the Magadha empire.
" The result of that expedition was that he sent as his ambassador to that monarch Megasthenes, from whom we drive some Knowledge of Indian Arms at that time. He describes the army as consisting of 400,000 men, including 20,000 cavalry and 2,000 chariots. The chief city was defended by 574 towers and a ditch 30 cubits deep and entered by 60 gates."
( ref pg 11 Illustrated Handbook of Indian Arms paragraph 3)
The Greek kingdom of Bactria was the link between India and the classic world.
Successors of this kingdom were the Indo-Scythian Kings, who ruled much of the Upper India states for a considerable time.
There influence was long felt and may be traced as far as Orissa.
"On the defeat of the Scythians by Vikramaditya several Hindoo dynasties shared Hindostan between them, but our knowledge of the military events of this period is extremely imperfect, and continues so until the time of the conquest of India by the Mahomedans."