In 310 BC, after an unsuccessful siege of the city of Bayblon by his son Demetrius, Antigonus decided to march against Seleucus himself. He mobilized an army of more than 75,000 men and marched towards Babylon. Seleucus, who had just reconquered Babylon, was heavily outnumbered, but emboldened by his earlier victories he decided to make a stand.