That it did not even get started was partly due to Ptolemy, who, impelled by the magnitude of his danger, took the desperate step of adding many natives to his army; and partly due to Demetrius, who, despite his numerical inferiority, his instructions, and the judgment of his staff officers, risked a pitched battle at Gaza, and was decisively defeated. That the project could never again be renewed on similarly advantageous terms was due to Seleucus, the son of Antiochus. For taking a thousand men with him this accomplished officer, old in service though still young in years, set out straightway after the battle of Gaza for Babylon, his own satrapy, whence he had fled to Egypt for fear of Antigonus four years earlier. Ten years afterwards, in 302 B.C., when Antigonus again proceeded to conquer Macedon and Thrace, after having beaten Ptolemy back into Egypt, his great aim was frustrated, not only because the king of Thrace, Lysimachus, outmanoeuvred him by getting an army across into Asia Minor, but also because Seleucus, now master of all the territory in the rear of Antigonus between the Euphrates and the frontiers of India, threw the decisive weight of his new army into the scale, and joined Lysimachus in crushing their common enemy at the great battle of Ipsus in 301 B.C. Thereby Seleucus advanced his western frontier from the Euphrates to the edge of the Mediterranean, shifted his capital from Babylon to newly founded Antioch, and brought his empire into immediate proximity with the districts whence alone Greek and Macedonian immigrants could come. The Seleucids dated the founding of their dynasty from the return of Seleucus to Babylon in 312 B.C. There is, however, much to be said for the view that their empire was first established after the battle of Ipsus. For the next twenty years (301-281 B.C.) Seleucus had the great good fortune to remain in secure possession of the vast territory which called him king; and while he failed to pass on to his descendants all the fruits of his crowning victory over Lysimachus at Corupedion in 282 B.C., he left to his son Antiochus I, surnamed Soter, or the Savior, and he in turn about twenty years later, to _his_ son Antiochus II, surnamed Theos, or the God, the fabric of their dominions, somewhat tattered at the edges, to be sure, but otherwise whole.