Babylonian War

The rise of Seleucus in Babylon threatened the eastern extent of Antigonus I territory in Asia. Antigonus, along with his son Demetrius I of Macedon, unsuccessfully led a campaign to annex Babylon. The victory of Seleucus ensured his claim of Babylon and legitimacy. He ruled not only Babylonia, but the entire enormous eastern part of Alexander's empire, as described by Appian: Always lying in wait for the neighboring nations, strong in arms and persuasive in council, he [Seleucus] acquired Mesopotamia, Armenia, 'Seleucid' Cappadocia, Persis, Parthia, Bactria, Arabia, Tapouria, Sogdia, Arachosia, Hyrcania, and other adjacent peoples that had been subdued by Alexander, as far as the river Indus, so that the boundaries of his empire were the most extensive in Asia after that of Alexander. The whole region from Phrygia to the Indus was subject to Seleucus.