Seleucus was appointed as the satrap of Babylon until he was forced to leave, fearing Antigonus increasing power in 315 BC and took refuge at Ptolemy's court, where he remained until he and Ptolemy defeated Antigonus's son Demetrius at Gaza in 312 BC, after which Ptolemy delivered to him 200 cavalry and 800 foot soldiers, and begun his advance towards his old satrapy of Babylon.