Long ago, a great city was called Babylon. 
Long ago, a king named Nabonidus ruled Babylon. 
A leader named Cyrus came from the east. He led a large army. Cyrus wanted to rule the land.
One night, the city was having a big party. The army used the river to enter. They took the city quickly.
Cyrus became the new king. He let many people go home. He was a very strong leader.
Babylon changed forever after that. It was a very big event.
A long time ago, the Neo-Babylonian Empire was very large. 
To the east, a leader named Cyrus the Great was growing strong. He led the Persian Empire. In 539 BCE, Cyrus began to move against Babylon. Some stories say the Persian army won a big battle at Opis. Then, they entered the city of Babylon.
Many writers tell different stories about how the city fell. Some say it was taken without a fight. Others say the army surprised the city during a big festival. Some say the Persians used the river to get inside.
Cyrus became the new king. He was kind to many people. He let exiles return to their own homes. He even let them take their sacred items with them. This helped him become a respected leader in the new empire.
The fall of Babylon was a major turning point in history. It happened in 539 BCE when the Persian Empire conquered the Neo-Babylonian Empire. This event ended the last native ruling family of Mesopotamia. It also gave the Persians control over the Fertile Crescent region. 
Many different groups of people were unhappy with Nabonidus. The priests of the god Marduk hated him for changing religious traditions. He favored the moon-god Sin instead of the local gods. The military class also disliked his scholarly interests. He spent a lot of time studying old temple records. He often left the defense of the kingdom to others. This made the people feel unsafe and ignored.
To the east, the Persian Empire was growing very fast. A leader named Cyrus the Great led the Achaemenid dynasty. He first rose to power by revolting against the Medes. By 540 BCE, Cyrus began attacking Babylon's eastern lands. He invaded Syria and took many Babylonian territories. The Persians were becoming a massive force in the region. This growing power led to a direct conflict with Babylon.
In late 539 BCE, the Persian army won at the Battle of Opis. After this victory, they entered the city of Babylon. Historians have different stories about how this happened. Some ancient texts say the city was taken without a fight. Other writers say the Persians surprised the city during a festival. One idea is that they moved the Euphrates River to enter through the riverbed. These different accounts make the exact moment of the fall a mystery.
Cyrus the Great became the new ruler of the region. He acted as a liberator to many people. He allowed exiled groups, like the Jews, to return to their homes. He even let them carry their sacred items back with them. Cyrus claimed he was chosen by the god Marduk to restore order. This helped him gain support from the local people. His rule changed how many different nations lived together under one empire.
The fall of Babylon in 539 BCE was a massive shift in ancient history. It marked the moment the Persian Empire conquered the Neo-Babylonian Empire. This conquest ended the reign of the last native Mesopotamian dynasty. It also gave the Persians control over the Fertile Crescent, a region of great importance. 
Nabonidus was the final king of the Neo-Babylonian Empire. He took the throne in 556 BCE after overthrowing Labashi-Marduk. Nabonidus was a complex leader with many different interests. He was a scholar who spent time excavating old temple records to find their dates. However, his interests often pulled him away from his duties as a king. He spent long periods in the southern deserts among his Arab subjects. He also spent time in the city of Harran to rebuild temples there. While he was away, he left the daily rule to his son, Belshazzar. Belshazzar was a capable soldier but a poor diplomat. His political choices caused him to lose the support of the military and the political elite.
Internal problems made Babylon vulnerable to outside threats. The priesthood of the god Marduk was very unhappy with Nabonidus. He had suppressed the cult of Marduk and elevated the moon-god Sin instead. He also tried to centralize religion at the temple of Marduk in Babylon. This move alienated many local priests. The military class also grew to despise him because of his scholarly focus. They felt he was neglecting the defense of the kingdom. Additionally, Nabonidus and Belshazzar had Assyrian heritage. This background likely added to the resentment felt by the Babylonian people.
To the east, the Achaemenid Persian dynasty was rising rapidly. Cyrus the Great was the leader of this growing power. Around 550/549 BCE, Cyrus revolted against the Medes at Ecbatana. After his victory, he became the king of all Persia. By 540 BCE, Cyrus began an offensive campaign against Babylon. He first invaded Syria and took many of Babylon's eastern possessions. Many of Babylon's vassal states fell under Persian authority during this time. Nabonidus was eventually forced to return to Babylon in 543 BCE to deal with constant Persian raids.
The final invasion occurred in 539 BCE. The Persian army won a major victory at the Battle of Opis. After this, they moved toward the city of Babylon. Historians disagree on exactly how the city fell. The Babylonian Chronicles and the Cyrus Cylinder claim the city was taken "without battle." However, Greek historians like Herodotus and Xenophon suggest the city was besieged. Some scholars propose a specific strategy for the capture. They suggest General Ugbaru led a force through the Enlil Gate on the west side of the Euphrates. The Persians may have diverted the river to enter through the riverbed. This would have allowed them to surprise the city during a festival.
Cyrus the Great used clever political moves to stabilize his new empire. He did not just act as a conqueror; he acted as a liberator. He allowed many exiled people, including the Jews, to return to their homes. He even permitted them to carry their sacred vessels and gods back with them. Cyrus claimed he was the legitimate successor to the Babylonian kings. He portrayed himself as the chosen savior of the god Marduk. This helped him gain the support of the Marduk priesthood. He even took the official title of "King of Babylon" to show his connection to the land.
The fall of Babylon led to long-term changes in the region. Babylon eventually became a colony of the Achaemenid Empire. Later, the Macedonian king Alexander the Great conquered the city in 331 BCE. After his death, the region was absorbed into the Seleucid Empire. Even as new empires rose, urban life in Babylon continued for a long time. The city remained a center of culture and patriotism through the Parthian age. The transition from native rule to Persian rule was a foundation for a new type of multi-national state. This system of government would eventually influence many future empires.
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