Little is known of the campaign, in which Chandragupta fought with Seleucus over the Indus Valley and the region of Gandhara, a very wealthy kingdom that had submitted decades earlier to Alexander the Great. The Mauryans seem to have got the better of the fighting, though no record survives. The region fell to the Mauryans; and Chandragupta also took over the Kashmir and the Hindu Kush. At the same time, Chandragupta expanded into the Deccan. Chandragupta took over the Punjab also, and by 303 BC he had taken over Eastern Afghanistan and everything in between. However, whether or not these territories were acquired by subsequent treaty with Seleucus or by military conquest is also unknown.
Seleucus' focus was not in the east, but in the west, where his greatest enemy, Antigonus I Monophthalmus, was attempting to crush all of his rivals and take complete control of Alexander's legacy. To end the losing war against the Mauryan Empire and focus his attention in the west, Seleucus negotiated a peace and ceded Alexander's Indian territories to Chandragupta. Later Selecus would form an alliance with the marriage of his daughter to Chandragupta, in return as dowry, Seleucus received 500 War Elephants, which would prove decisive in the conflict ahead, culminating in the Battle of Ipsus.
The peace was negotiated by the Greek envoy, Megasthenes. He made several journeys into the Mauryan Empire, chronicling his journeys.
Chandragupta converted to Jainism and abdicated his throne as part of his faith around 298 BC. His empire includes most of India (the southern-most regions were left unconquered). He was succeeded by his son, Bindusara. Mysore was taken by Bindusara, the empire reaching its expansion zenith.
For the Seleucids, the war affected the Wars of the Diadochi in the west. With the elephant force acquired from the Maurya, Seleucus was able to defeat his rival, Antigonas, at the Battle of Ipsus. Adding Antigonas' territories to his own, Seleucus would found the Seleucid Empire; which endured as a great power in the Mediterranean and the Middle East till 64 BCE.
- R.G. Grant: Commanders pg. 49