Seleucus I Nicator began life as a Macedonian noble and a junior officer in the army of Alexander the Great. He ended it as the founder of the Seleucid Empire, and came close to reunited Alexander’s empire under his rule. In the period immediately after Alexander’s death, Seleucus served as an officer in the army of Perdiccas, taking part in his murder during a botched invasion of Egypt.
Seleucus began his close association with his future empire in 321 BC, when he was appointed satrap of Babylon. Under Alexander Babylon had been the potential future capital of the empire – for most of his successors it was an eastern backwater. Seleucus retained more of Alexander’s eastern ambitions – he was the only one of the senior successors not to repudiate the Iranian wives Alexander had given then all.
Seleucus remained in command in Babylon until 315. In that year he was forced out of his satrapy by Antigonus Monophthalmus, who had emerged from the first round of fighting between the successors in a very strong position, controlling Asia Minor, Syria and now the east. Seleucus fled to Ptolemy, where he found refuge and support.
Ptolemy was always opposed to anyone who might become powerful enough to threaten his rule in Egypt. In 315 that figure was Antigonus. The same was true for Cassander and Lysimachus, and together they issued an ultimatum to Antigonus. He refused their terms, triggering the Third Diadoch War. He then left his son Demetrius to defend his position in southern Syria and Palestine.
Seleucus spent the next three years in Egypt, waiting for Ptolemy to act. Finally, in 312 Ptolemy was ready. He inflicted a heavy defeat on Demetrius (battle of Gaza), opening to road back to Babylon. Seleucus took his chance, returning to Babylon where he quickly regained power. The defeat at Gaza forced Antigonus to make peace with Cassander and Lysimachus, soon joined by Ptolemy. The peace of 311 did not include Seleucus.
One of the most obscure of Hellenic Wars followed (Babylonian War). Antigonus invaded Babylonia, but was defeated in a battle whose date and location is unclear. It was probably fought close to Babylon in 309/8, but we can not be sure. The future actions of both men suggests that they made peace in 308.
Fourth Diadoch War
From 308 Seleucus concentrated on the eastern borders of his empire, where he was involved in a war with Chandragupta, the Mauryan ruler. This lasted until some time in 305-3, when Seleucus surrendered the far east of his empire to Chandragupta in return for five hundred war elephants.
In 305 Seleucus finally adopted the royal title, following Antigonus, who had made the move after the conquest of Cyprus (306 BC).
The successes of Antigonus and Demetrius may have triggered this peace. Seleucus joined the great coalition against Antigonus, bringing his elephants to the battlefield at Ipsus (301 BC). In the aftermath of that victory, Seleucus was granted Syria. Ptolemy had been promised the south of Syria, but had not appeared at Ipsus, so Seleucus had been given the entire area. However, during 301 Ptolemy had seized southern Syria, as far as the River Eleutherus (now the northern border of the Lebanon). This southern area now became known as Coele-Syria, and would remain a source of tension between Egypt and the Seleucid Empire. For the moment any conflict was avoided by Seleucus, who did not oppose Ptolemy’s possession of the area in recognition of the debt he owned to him.
In the aftermath of Ipsus, the focus of Seleucus’s empire moved west to northern Syria. In 300 he founded a new western capital at Antioch by moving Antigoneia, recently founded by Antigonus, as well as Seleucia-in-Pieria, the port of Antioch. This area would become the heart of the Seleucid Empire.
For the next few years events were dominated by the adventures of Demetrius in Greece and Macedonia. In 288 Seleucus was expelled from Macedonia and embarked on an adventure that ended in Cilicia in 286. There he was eventually trapped, outnumbered and forced to surrender. Unusually Seleucus kept him alive, in a gilded cage on the Orontes. Three years later Demetrius died after three years of uninterrupted debauchery.
Late in live Seleucus was given an unexpected chance to reunite most of Alexander’s empire. Lysimachus had become king of Macedonia after 288, but quickly made himself unpopular, not least by executing his son and heir. His widow fled to Seleucus, who now found himself pressured to intervene in Macedonia. Late in 282 he invaded Asia Minor, where he was greeted with offers of assistance. The next year he defeated Lysimachus at the battle of Corupedium (281 BC). Lysimachus was killed during the battle.
In the aftermath Seleucus found himself ruler of Asia Minor, and in a strong position to take Macedonia. He waited until 280 to travel to Macedonia, but he never reached his destination. Soon after landing on the European shore of the Hellespont, Seleucus was murdered by Ptolemy Keraunos, who went on to seize power in Macedonia himself. Seleucus was succeeded by his son Antiochus I Soter, who retained most of Asia Minor.