In 539 BCE, Cyrus the Great conquered Babylon and brought the Neo-Babylonian Empire under Persian rule. The victory gave Cyrus control of Mesopotamia and transformed the Achaemenid kingdom into the largest imperial power of its age.
The Kingdom of Nabonidus
Babylon was ruled by Nabonidus, the final king of the Neo-Babylonian dynasty. His religious policies and long absence from the capital may have created tensions with Babylon’s priesthood and political elite, although surviving accounts often reflect the propaganda of his opponents.
Cyrus presented himself as a legitimate and divinely favoured alternative. Persian propaganda claimed that Babylon’s chief god, Marduk, had rejected Nabonidus and selected Cyrus to restore order and protect the city’s religious traditions.
The Battle of Opis
The decisive Persian campaign began in the autumn of 539 BCE. Cyrus defeated the Babylonian army near Opis on the Tigris River. The Babylonian Chronicle associates the battle with heavy bloodshed, showing that the conquest of the kingdom was not entirely peaceful.
After the defeat at Opis, the strategically important city of Sippar surrendered without a battle. Nabonidus fled, leaving the road to Babylon open to the Persian forces.
The Entry into Babylon
On 12 October 539 BCE, troops commanded by Ugbaru, the governor of Gutium, entered Babylon without a major battle inside the city. Nabonidus was captured, and guards were reportedly placed around important temples to maintain order and protect religious ceremonies.
Cyrus entered Babylon several weeks later. The Babylonian Chronicle describes a peaceful reception, while the Cyrus Cylinder presents him as a liberator welcomed by the population. These sources were produced within the new political order and should be read as carefully constructed statements of royal legitimacy.
Cyrus as King of Babylon
Cyrus adopted traditional Mesopotamian royal titles, including King of Babylon and King of the Four Quarters. Rather than abolishing Babylonian institutions, he worked through existing administrators, priests and scribes.
The Cyrus Cylinder states that displaced divine images were returned to their sanctuaries and that communities were restored to their homelands. These policies followed established Mesopotamian traditions of presenting a new ruler as the restorer of temples and proper religious order.
A Turning Point in Imperial History
The capture of Babylon gave Cyrus access to the wealth, cities and administrative traditions of Mesopotamia. It also extended Persian authority into Syria and the eastern Mediterranean territories formerly controlled by the Babylonian kings.
Babylon remained one of the most important cities of the Achaemenid Empire. Its conquest demonstrated Cyrus’s ability to combine military victory with political accommodation, helping him govern a vast and culturally diverse realm.