In May 311, Seleucus unexpectedly captured Babylon, the greatest city in the world and one of the most important parts in the empire of Antigonus Monophthalmus. In the autumn of 311, he sent his son Demetrius to expell Seleucus. His expedition did not reach its aims.
The story is told by Diodorus of Sicily (World history, 19.100.5-7). The translation was made by Russel Geer.
Demetrius' Babylonian campaign
[19.100.5] So Demetrius, having set out from Damascus in Syria, carried out his father's orders with zeal. Patrocles, who had been established as general of Babylonia by Seleucus, hearing that the enemy was on the frontiers of Mesopotamia, did not dare await their arrival since he had few men at hand; but he gave orders to the civilians to leave the city, bidding some of them cross the Euphrates and take refuge in the desert and some of them pass over the Tigris and go into Elam to Euteles and to the Red Sea;note[Euteles may have been Seleucus' commander in Elam; the Red Sea is the ancient name of the Persian Gulf.]
[19.100.6] and he himself with what soldiers he had using river courses and canals as defenses, kept moving about in the satrapy, watching the enemy and at the same time sending word into Media to Seleucus about what was taking place from time to time and urging him to send aid as soon as possible.
[19.100.7] When Demetrius on his arrival at Babylon found the city abandoned, he began to besiege the citadels. He took one of these and delivered it to his own soldiers fur plundering; the other he besieged for a few days and then, since the capture required time, left Archelaus, one of his friends, as general for the siege, giving him 5,000 infantry and 1,000 cavalry, while he himself, the time being close at hand at which he had been ordered to return, made the march down to the seanote[The Mediterranean Sea.] with the rest of the army.