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311 BCEReputable source · 2 sourcesWell documented

Seleucus Founds the Seleucid Empire from Babylon

One of Alexander's generals fights his way back into Babylon and builds the empire that governs Persia for the next century

On the timeline · around 311 BCE · Alexander, the Seleucids, and the Parthian EmpireXerxes, the Greco-Persian Wars, and the Later AchaemenidsAlexander, the Seleucids, and the Parthian EmpireSeleucus Founds the Seleucid Empire from Babylon350 BCE300 BCE250 BCE200 BCE150 BCE

Quick facts

Founder
Seleucus I Nicator
Capture of Babylon
May 311 BCE
Capitals founded c. 300 BCE
Antioch and Seleucia on the Tigris
Territory
Former Persian and Median lands, Mesopotamia, Levant

What happened

After Alexander's death in 323 BCE, his empire fractured among his generals, the Diadochi. Seleucus was made satrap of Babylon at the Partition of Triparadisus in 321 BCE, but the more powerful general Antigonus forced him to flee. With support from Ptolemy, Seleucus returned and captured Babylon in May 311 BCE during what is called the Babylonian War, then claimed to rule as viceroy for Alexander's infant son Alexander IV. From 312 BCE onward Seleucus expanded ruthlessly, eventually controlling the former Persian and Median territories along with Mesopotamia and much of the Levant, and founded twin capitals around 300 BCE at Antioch in Syria and Seleucia on the Tigris in Mesopotamia, deliberately shifting the empire's center of gravity toward the Mediterranean and away from the old Achaemenid heartland in Fars.

Why it matters

The Seleucid Empire governed Iran and Mesopotamia as a Greek-ruled successor state for over a century, introducing Greek cities and colonists across the former Achaemenid territory. Its founding of a capital far from Persia proper left the Iranian plateau itself relatively loosely governed, the exact opening that Parthian nomads from the northeast would later exploit.

How we know

The main narrative survives through later Greek and Roman historians, particularly Appian's account of Seleucus's career, cross-checked against the Babylonian Astronomical Diaries, contemporary cuneiform records that independently date Seleucus's capture of Babylon.

Sources

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Part of a timelineAncient Persia27 events · Three empires in a row, Achaemenid, Parthian, and Sassanid, ran the largest state the ancient world had seen and left cuneiform, coinage, and a fire religion behindView all →