Battle of Ipsus
Chandragupta and Seleucus concluded a peace treaty and a marriage alliance in 303 BCE. Chandragupta received vast territories and in a return gave Seleucus 500 war elephants, a military asset which would play a decisive role at the Battle of Ipsus in 301 BCE. In addition to this treaty, Seleucus dispatched an ambassador, Megasthenes, to Chandragupta, and later Deimakos to his son Bindusara, at the Mauryan court at Pataliputra (modern Patna in Bihar). Later, Ptolemy II Philadelphus, the ruler of Ptolemaic Egypt and contemporary of Ashoka, is also recorded by Pliny the Elder as having sent an ambassador named Dionysius to the Mauryan court.