Seleucid Empire

The Seleucid Empire (/sɪˈljuːsɪd/ sih-LEW-sid) was a Greek state in West Asia during the Hellenistic period. It was founded in 312 BC by the Macedonian general Seleucus I Nicator, following the division of the Macedonian Empire founded by Alexander the Great, and ruled by the Seleucid dynasty until its annexation by the Roman Republic under Pompey in 63 BC.

After receiving the Mesopotamian regions of Babylonia and Assyria in 321 BC, Seleucus I began expanding his dominions to include the Near Eastern territories that encompass modern-day Iraq, Iran, Afghanistan, Syria, and Lebanon, all of which had been under Macedonian control after the fall of the former Achaemenid Empire. At the Seleucid Empire's height, it had consisted of territory that covered Anatolia, Persia, the Levant, Mesopotamia, and what are now modern Kuwait, Afghanistan, and parts of Turkmenistan.

The Seleucid Empire was a major center of Hellenistic culture. Greek customs and language were privileged; the wide variety of local traditions had been generally tolerated, while an urban Greek elite had formed the dominant political class and was reinforced by steady immigration from Greece. The empire's western territories were repeatedly contested with Ptolemaic Egypt—a rival Hellenistic state. To the east, conflict with the Indian ruler Chandragupta of the Maurya Empire in 305 BC led to the cession of vast territory west of the Indus and a political alliance.

In the early second century BC, Antiochus III the Great attempted to project Seleucid power and authority into Hellenistic Greece, but his attempts were thwarted by the Roman Republic and its Greek allies. The Seleucids were forced to pay costly war reparations and had to relinquish territorial claims west of the Taurus Mountains in southern Anatolia, marking the gradual decline of their empire. Mithridates I of Parthia conquered much of the remaining eastern lands of the Seleucid Empire in the mid-second century BC, including Assyria and what had been Babylonia, while the independent Greco-Bactrian Kingdom continued to flourish in the northeast. The Seleucid kings were thereafter reduced to a rump state in Syria after a civil war, until their conquest by Tigranes the Great of Armenia in 83 BC, and ultimate overthrow by the Roman general Pompey in 63 BC.

Contemporary sources, such as a loyalist decree honoring Antiochus I from Ilium, in Greek language define the Seleucid state both as an empire (ἀρχή, archḗ) and as a kingdom (βασιλεία, basileía). Similarly, Seleucid rulers were described as kings in Babylonia.

The rulers did not describe themselves as being of any particular territory or people, but starting from the 2nd century BC, ancient writers referred to them as the Syrian kings, the kings of Syria or of the Syrians, the kings descended from Seleucus Nicator, the kings of Asia, and other designations.

Alexander, who quickly conquered the Persian Empire under its last Achaemenid dynast, Darius III, died young in 323 BC, leaving an expansive empire of partly Hellenised culture without an adult heir. The empire was put under the authority of a regent, Perdiccas, and the vast territories were divided among Alexander's generals, who thereby became satraps at the Partition of Babylon, all in that same year.

Alexander's generals, known as diadochi, jostled for supremacy over parts of his empire following his death. Ptolemy I Soter, a former general and then current satrap of Egypt, was the first to challenge the new system, which eventually led to the demise of Perdiccas. Ptolemy's revolt created a new subdivision of the empire with the Partition of Triparadisus in 320 BC. Seleucus, who had been "Commander-in-Chief of the Companion cavalry" (hetairoi) and appointed first or court chiliarch (which made him the senior officer in the Royal Army after the regent and commander-in-chief Perdiccas since 323 BC, though he helped to assassinate him later) received Babylonia and, from that point, continued to expand his dominions ruthlessly. Seleucus established himself in Babylon in 312 BC, the year later used as the foundation date of the Seleucid Empire.