A Journey Through Iran’s Historic Wars from Antiquity to Today – Part Two: The Conquest of Babylon (539 BCE)

When Cyrus the Great vanquished the Lydian kingdom in the west, stretching his dominion to the shores of the Mediterranean, only one colossal power stood before him: the Neo-Babylonian Empire. Babylon was more than a military foe; it was the pulsating heart of Mesopotamian civilization, the nexus of global trade, and a symbol of authority that had reigned over the region for millennia. The conquest of Babylon was the ultimate trial for Cyrus and his fledgling Achaemenid Empire, a feat that would etch his name into the annals of history.

Picture the legendary Hanging Gardens, gleaming under the Mesopotamian sun, and the towering ziggurat of Etemenanki, famed in lore as the Tower of Babel. At its zenith, Babylon was a marvel of urban civilization. Yet, the tale of its conquest by Cyrus is no mere military account; it is a masterclass in strategy, revealing how a shrewd conqueror, wielding a blend of military might, psychological warfare, and diplomacy, captured the greatest city of the ancient world not through a bloody siege but by having its gates flung open in welcome.

Historical Context: Babylon on the Brink of Collapse

In 539 BCE, the Neo-Babylonian Empire was a giant afflicted with malaise. Under Nebuchadnezzar II (605–562 BCE), Babylon had soared to its peak, conquering Jerusalem and erecting wonders like the Hanging Gardens (if they truly existed). But under its final king, Nabonidus (556–539 BCE), the empire was beset by internal crises.

Babylon’s defences appeared impregnable: double-layered walls, some 20 meters thick, a moat fed by the Euphrates, and vast storehouses of provisions primed for a prolonged siege. Yet, within these steadfast walls, a society riven by division and a crisis of leadership faltered. Nabonidus, with his unorthodox religious policies favouring the moon god Sin over Marduk, Babylon’s national deity, turned the powerful priesthood of Marduk into bitter adversaries. His decade-long absence in the oasis of Tayma (modern-day Saudi Arabia), leaving his son Belshazzar in charge, stripped him of legitimacy among the people and elites. Babylonian inscriptions, such as the Babylonian Chronicle, recount Nabonidus’s neglect of sacred rituals like the Akitu festival, fueling public outrage.

Cyrus, with keen insight, targeted these fractures. His propaganda, proclaiming him as Marduk’s chosen saviour of Babylon, spread through the city, planting seeds of hope among the discontented. His message was clear: restore order, honour traditions, and end Nabonidus’s illegitimate rule. This psychological campaign established Cyrus as a pioneer of media strategy in the ancient world.

The Campaign and the Fall of Babylon

In the autumn of 539 BCE, Cyrus’s army marched toward Babylon. The first significant clash unfolded at Opis, on the banks of the Tigris. With superior tactics and by exploiting the Babylonians’ weakened morale, the Persians crushed Nabonidus’s forces. The Babylonian Chronicle speaks of a great slaughter that shattered Babylon’s military backbone. Contrary to the popular tale of a bloodless conquest, the road to Babylon was stained with the blood of soldiers and civilians alike.

Following the triumph at Opis, the city of Sippar surrendered without a fight. Nabonidus fled to the capital, now a ruler trapped in a town bereft of an army and mired in a crisis of legitimacy. On October 12, 539 BCE, Cyrus’s general, Ugbaru (or perhaps Gobryas, possibly a Babylonian defector), entered Babylon. According to the Babylonian Chronicle and Herodotus, the Persians diverted the Euphrates, lowering its waters to allow troops to infiltrate via the riverbed. The gates—likely opened by priests or dissidents—swung wide, and the city fell without significant resistance. Seventeen days later, Cyrus himself entered Babylon, proceeding to the temple of Marduk to proclaim himself a rightful king.

The Cyrus Cylinder: A Testament to Strategy

Following Mesopotamian custom, Cyrus commissioned a clay cylinder inscribed in Akkadian cuneiform, likely buried beneath Marduk’s temple to immortalize his legitimacy. Unearthed in 1879 by British archaeologists, this cylinder, now housed in the British Museum, is a cornerstone of history. Far from modern interpretations as a “charter of human rights,” it is a masterful royal proclamation tailored to win the hearts of Babylon’s people and elites. Dr. Shahrokh Razmjou’s translation captures its essence:

“Marduk… sought a just king across all lands… He grasped the hand of Anshan’s king, Cyrus, calling him by name… He entrusted the rule of the world to him… He [Cyrus] restored the gods to their sanctuaries and rebuilt their ruined temples.”

This narrative cast Cyrus not as a foreign invader but as a liberator of Babylonian traditions, chosen by Marduk, easing his acceptance among the populace. The cylinder’s impact echoed far beyond Babylon: in the Book of Ezra in the Old Testament, Cyrus is lauded as God’s anointed, granting exiled Jews permission to return to Jerusalem and rebuild their temple. Some scholars, such as Ibn Hisham, suggest that this glowing image of Cyrus may have inspired the Qur’anic figure of Dhul-Qarnayn, although this hypothesis remains speculative and debated.

Legacy and Achievements of the Conquest

Cyrus’s conquest of Babylon was more than a military victory; it was the capture of a civilization’s heart, the cradle of writing, law (such as Hammurabi’s Code), and urban systems. Babylon’s fall in 539 BCE transformed the Achaemenid Empire into a global superpower, spanning from Ionia’s coasts to the plains of the Tigris and Euphrates. Babylon’s treasure trove of knowledge—astronomy, mathematics, medicine, and engineering—enriched the Persian realm. Its sophisticated administrative systems, from archives to city governance, became a model for the Achaemenid satrapy system, enabling the rule of a vast, multicultural domain.

Cyrus’s policy of tolerance forged a new paradigm for empire-building. Unlike conquerors who razed cities or enslaved peoples, he respected local faiths and customs. This approach not only pacified Babylon but also inspired loyalty among its inhabitants. His decree freeing the Jewish exiles, as recorded in the Old Testament, exemplifies this philosophy. Later conquerors, from Alexander the Great to Roman emperors, drew inspiration from this model of multicultural governance.

When Cyrus passed through Babylon’s Ishtar Gate, he did more than conquer a city—he inherited a civilization. His empire, now stretching from the Mediterranean to the Euphrates, became a crucible of cultures, ideas, and innovations. The conquest of Babylon elevated the Persians from a regional power to a global empire, not through destruction but through synergy. Cyrus’s legacy teaches that actual conquest lies in opening hearts, not breaching walls. Enduring empires are built on trust and respect for cultures, not on ruins. Thus, when a regime loses its place in the hearts and minds of its people, when its bulwarks in their thoughts crumble, it fights only shadows in the streets or on the fields of battle.

Recommended Reading: For deeper insight into the Cyrus Cylinder, The Cyrus Cylinder and Ancient Persia (edited by Irving Finkel, British Museum) is a reliable source.