After Alexander's death in 323 BC, Chandragupta, turned his attention to Northwestern India (modern Pakistan), where he defeated the satrapies (described as "prefects" in classical Western sources) left in place by Alexander (according to Justin), and may have assassinated two of his governors, Nicanor and Philip.[3][31] The satrapies he fought may have included Eudemus, ruler in western Punjab until his departure in 317 BC; and Peithon, son of Agenor, ruler of the Greek colonies along the Indus until his departure for Babylon in 316 BC. The Roman historian Justin described how Sandrocottus (Greek version of Chandragupta's name) conquered the northwest:
"India, after the death of Alexander, had assassinated his prefects, as if shaking the burden of servitude. The author of this liberation was Sandracottos, but he had transformed liberation in servitude after victory, since, after taking the throne, he himself oppressed the very people he has liberated from foreign domination."
Junianus Justinus, Historiarum Philippicarum libri XLIV, XV.4.12-13
"He was of humble origin, but was pushing to acquiring the throne by the superior power of the mind. When after having offensed the king of Nanda by his insolence, he was condemned to death by the king, he was saved by the speed of his own feet"
Junianus Justinus, Historiarum Philippicarum libri XLIV, XV.4.15
"Later, as he was preparing war against the prefects of Alexander, a huge wild elephant went to him and took him on his back as if tame, and he became a remarkable fighter and war leader. Having thus acquired royal power, Sandracottos possessed India at the time Seleucos was preparing future glory."
Junianus Justinus, Historiarum Philippicarum libri XLIV, XV.4.19
Having consolidated power in the northwest, Chandragupta pushed east towards the Nanda Empire.