Due to the internal conflicts between Alexander's generals, Chandragupta saw an opportunity to expand the Mauryan Empire from its Ganges Plain heartland by defeating Nanda Dynasty one of the Mahajanpadas of that time towards the Indus Valley between 325 BCE to 303 BCE. At the same time, Seleucus I now ruler much of the Macedonian Empire was advancing from Babylon in order to establish his writ in the former Persian and Indus Valley provinces of Alexander. During this period, Chandragupta's mercenaries may have assassinated Satrap of Punjab Philip. They presumably also fought Eudemus, Porus and Taxiles of Punjab and Peithon of Sindh. In 316 BCE, both Eudemus and Peithon left Punjab and Sindh for Babylon, thus ending Macedonian rule. The Mauryan Empire now controlled Punjab and Sindh. As the Seleucid Empire expanded eastwards towards the Indus, it was becoming more difficult for Seleucus to assert control over the vast eastern domains. Seleucus invaded Punjab in 305 BC, confronting Chandragupta Maurya. It is said that Chandragupta fielded an army of 600,000 men and 9,000 war elephants. After two years of war, Chandragupta was successful in defeating Seluecus , so Seleucus reached an agreement with Chandragupta, in which he gave his daughter in marriage to Chandragupta and exchanged his eastern provinces for a considerable force of 500 war elephants, which would play a decisive role at The Battle of Ipsus (301 BCE). Strabo, in his Geographica, wrote: