Battle of Ipsus
In 305 BC, Seleucus I led an army to the Indus, where he encountered Chandragupta. The confrontation ended with a peace treaty, and "an intermarriage agreement" (Epigamia, Greek: Ἐπιγαμία), meaning either a dynastic marriage or an agreement for intermarriage between Indians and Greeks. Accordingly, Seleucus ceded to Chandragupta his northwestern territories, possibly as far as Arachosia and received 500 war elephants (which played a key role in the victory of Seleucus at the Battle of Ipsus):