Chandragupta Maurya defeated Seleucus Nicator (Seleucus I) around 305-303 BCE. After this defeat, Seleucus ceded territories of Afghanistan, Baluchistan, and eastern Persia to Chandragupta, and received 500 war elephants in return. Alexander died years before Chandragupta's rise, and Porus was defeated by Alexander, not Chandragupta.