His attempt, however, to restore Macedonian rule beyond the Indus, where the native Chandragupta had established himself, was not successful. Seleucus entered the Punjab, but felt himself obliged in 302 to conclude a peace with Chandragupta, by which he ceded large districts of Afghanistan in return for 500 elephants. The pressing need for Seleucus once more to take the field against Antigonus was at any rate in large measure the cause of his abandonment of India. In 301 he joined Lysimachus in Asia Minor, and at Ipsus Antigonus fell before their combined power. A new partition of the empire followed, by which Seleucus added to his kingdom Syria, and perhaps some regions of Asia Minor. The possession of Syria gave him an opening to the Mediterranean, and he immediately founded here the new city of Antioch upon the Orontes as his chief seat of government. His previous capital had been the city of Seleucia which he had founded upon the Tigris (almost coinciding in site with Bagdad), and this continued to be the capital for the eastern satrapies. About 293 he installed his son Antiochus there as viceroy, the vast extent of the empire seeming to require a double government. The capture of Demetrius in 285 added to Seleucus's prestige. The unpopularity of Lysimachus after the murder of Agathocles gave Seleucus an opportunity for removing his last rival. His intervention in the west was solicited by Ptolemy, Ceraunus, who, on the accession to the Egyptian throne of his brother Ptolemy II. (285), had at first taken refuge with Lysimachus and then with Seleucus. War between Seleucus and Lysimachus broke out, and on the field of Corupedion in Lydia Lysimachus fell (281). Seleucus now saw the whole empire of Alexander, Egypt alone excepted, in his hands, and moved to take possession of Macedonia and Thrace. He intended to leave Asia to Antiochus and content himself for the remainder of his days with the Macedonian kingdom in its old limits. He had, however, hardly crossed into the Chersonese when he was assassinated by Ptolemy Ceraunus near Lysimachia (281).
Antiochus I. Soter (324 or 323–262) was half a Persian, his mother Apame being one of those eastern princesses whom Alexander had given as wives to his generals in 324. On the assassination of his father (281), the task of holding together the empire was a formidable one, and a revolt in Syria'broke out almost immediately. With his father's murderer, Ptolemy, Antiochus was soon compelled to make peace, abandoning apparently Macedonia and Thrace. In Asia Minor he was unable to reduce Bithynia or the Persian dynasties which ruled in Cappadocia. In 278 the Gauls broke into Asia Minor, and a victory which Antiochus won over these hordes is said to have been the origin of his title of Soter (Gr. for “saviour”). At the end of 275 the question of Palestine, which had been open between the houses of Seleucus and Ptolemy since the partition of 301, led to hostilities (the “First Syrian War”). It had been continuously in Ptolemaic occupation, but the house of Seleucus maintained its claim. War did not materially change the outlines of the two kingdoms, though frontier cities like Damascus and the coast districts of Asia Minor might change hands. About 262 Antiochus tried to break the growing power of Pergamum by force of arms, but suffered defeat near Sardis and died soon afterwards (262). His eldest son Seleucus, who had ruled in the east as viceroy from 275 (?) till 268/7, was put to death in that year by his father on the charge of rebellion (Wace, J. H. S. xxv., 1905, p. 101 f.). He was succeeded (261) by his second son Antiochus II. Theos (286–246), whose mother was the Macedonian princess Stratonice, daughter of Demetrius Poliorcetes. War with Egypt still went on along the coasts of Asia Minor (the “Second Syrian War”). Antiochus also made some attempt to get a footing in Thrace. About 250 peace was concluded between Antiochus and Ptolemy II., Antiochus repudiating his wife Laodice and marrying Ptolemy's daughter Berenice, but by 246 Antiochus had left Berenice and her infant son in Antioch to live again with Laodice in Asia Minor. Laodice poisoned him and proclaimed her son Seleucus II. Callinicus (reigned 246–227) king, whilst her partisans at Antioch made away with Berenice and her son. Berenice's brother, Ptolemy III., who had just succeeded to the Egyptian throne, at once invaded the Seleucid realm and marched victoriously to the Tigris or beyond, receiving the submission of the eastern provinces, whilst his fleets swept the coasts of Asia Minor. In the interior of Asia Minor Seleucus maintained himself, and when Ptolemy returned to Egypt he recovered Northern Syria and the nearer provinces of Iran. In Asia Minor his younger brother Antiochus Hierax was put up against him by a party to which Laodice herself adhered. At Ancyra (about 235?) Seleucus sustained a crushing defeat and left the country beyond the Taurus to his brother and the other powers of the peninsula. Of these Pergamum now rose to greatness under Attalus I., and Antiochus Hierax perished as a fugitive in Thrace in 228/7. A year later Seleucus was killed by a fall from his horse. His elder son, Seleucus III. Soter (reigned 227-223), took up the task of reconquering Asia Minor from Attalus, but fell by a conspiracy in his own camp.
Antiochus III. the Great (242-187), Callinicus's younger son, a youth of about eighteen, now succeeded to a disorganized kingdom (223). Not only was Asia. Minor detached, but the further eastern provinces had broken away, Bactria under the Greek Diodotus (q.v.), and Parthia under the nomad chieftain Arsaces. Soon after Antiochus's accession, Media and Persis revolted under their governors, the brothers Molon and Alexander. The young king was in the hands of the bad minister Hermeias, and was induced to make an attack on Palestine instead of going in person to face the rebels. The attack on Palestine was a fiasco, and the generals sent against Molon and Alexander met with disaster. Only in Asia Minor, where the Seleucid cause was represented by the king's cousin, the able Achaeus, was its prestige restored and the Pergamene power driven back to its earlier limits. In 221 Antiochus at last went east, and the rebellion of Molon and Alexander collapsed. The submission of Lesser Media, which had asserted its independence under Artabazanes, followed. Antiochus rid himself of Hermeias by assassination and returned to Syria (220). Meanwhile Achaeus himself had revolted and assumed the title of king in Asia Minor. Since, however, his power was not well enough grounded to allow of his attacking Syria, Antiochus considered that he might leave Achaeus for the present and renew his attempt on Palestine. The campaigns of 219 and 218 carried the Seleucid arms almost to the confines of Egypt, but in 217 Ptolemy IV. confronted Antiochus at Raphia and inflicted a defeat upon him which nullified all Antiochus's successes and compelled him to withdraw north of the Lebanon. In 216 Antiochus went north to deal with Achaeus, and had by 214 driven him from the field into Sardis. Antiochus contrived to get possession of the person of Achaeus (see Polybius), but the citadel held out till 213 under Achaeus's widow and then surrendered. Having thus recovered the central part of Asia Minor—for the dynasties in Pergamum, Bithynia and Cappadocia the Seleucid government was obliged to tolerate—Antiochus turned to recover the outlying provinces of the north and east. Xerxes of Armenia was brought to acknowledge his supremacy in 212. In 209 Antiochus invaded Parthia, occupied the capital Hecatompylus and pushed forward into Hyrcania. The Parthian king was apparently granted peace on his submission. In 209 Antiochus was in Bactria, where the original rebel had been supplanted by another Greek Euthydemus (see further Bactria and articles on the separate rulers). The issue was again favourable to Antiochus. After sustaining a famous siege in his capital Bactra (Balkh), Euthydemus obtained an honourable peace by which the hand of one of Antiochus's daughters was promised to his son Demetrius. Antiochus next, following in the steps of Alexander, crossed into the Kabul valley, received the homage of the Indian king Sophagasenus and returned west by way of Seistan and Kerman (206/5). From Seleucia on the Tigris he led a short expedition down the Persian Gulf against the Gerrhaeans of the Arabian coast (205/4). Antiochus seemed to have restored the Seleucid empire in the east, and the achievement brought him the title of “the Great King.” In 205/4 the infant Ptolemy V. Epiphanes succeeded to the Egyptian throne, and Antiochus concluded a secret pact with Philip of