Answer
Seleucus returned to Babylon in 312 BC after a successful campaign against Antigonus I Monophthalmus. He had been exiled from Babylon by Antigonus in 316 BC, but he regained control of the city after defeating Antigonus at the Battle of Ipsus in 301 BC. Seleucus's return to Babylon marked the beginning of the Seleucid Empire, which ruled over much of the Middle East for over two centuries.