People of southern Mesopotamia who led a revolt against the Assyrian Empire in the first millennium B.C.E. and

established the Neo-Babylonian Empire. The Chaldeans were one of many militaristic peoples in Mesopotamia living in the shadow of the Assyrians.

Upon the death of the Assyrian ruler Ashurbanipal (r. ca. 669–627 B.C.E.), the Chaldeans, under their leader Nabopolassar (r. 626–605 B.C.E.), attacked and conquered Assyrian territory including the city of Babylon. The Chaldeans received assistance from the Medes, a people living in what is now Iran, who were challenging Assyrian dominance over the region. In 609 B.C.E., Nabopolassar captured the Assyrian capital city of Nineveh, thus completing the destruction of the Assyrian Empire.

Nabopolassar's son, Nebuchadrezzar II (r. 604–562 B.C.E.), succeeded his father as king of the Neo-Babylonian Empire and became the most prominent of the Neo-Babylonian kings. He united the Chaldeans with the Medes by marrying the daughter of the Medean king, and spent his reign expanding Babylonian power. In 597 B.C.E., Nebuchadrezzar attacked the Kingdom of Judah and captured Jerusalem. After putting down a popular rebellion there in 586 B.C.E., he punished the inhabitants by taking their lands and homes and forcing them to move in small groups to other places in his kingdom. This event, known as the Babylonian captivity, lasted until ca. 538 B.C.E., when the Persian Empire defeated the Babylonians and allowed the Jews to return to their homeland.

Although an eager and successful warrior, Nebuchadrezzar spent much of his reign rebuilding Nineveh and Babylon and erecting temples, libraries, and new defensive walls. Under his reign, Babylon grew to cover more than 500 acres (200 hectares) with city walls wide enough for two chariots to run side by side alongside their tops. However, the building project with which Nebuchadrezzar is most often associated, the Hanging Gardens of Babylon, may not have existed. Supposedly built around 660 B.C.E., the gardens were said to have covered acres with terraced planting beds and included an artificial lake.

Nebuchadrezzar was succeeded by a series of weak kings who were unable to maintain control over the territory that he and Nabopolassar had conquered. In 538 B.C.E., King Cyrus II, the Great, of Persia (r. ca. 559–ca. 530 B.C.E.) combined forces with the Chaldeans’ former allies, the Medes, to topple the Neo-Babylonian Empire.