Nabopolassar was a Chaldean king of Babylonia and a central figure in the fall of the Neo-Assyrian Empire. The death of Assyrian king Ashurbanipal in 631 BC resulted in political instability. In 626 BC, a native dynasty arose under Nabopolassar. He made Babylon his capital and ruled over Babylonia for a period of about twenty years. He is credited with founding the Neo-Babylonian Empire. By 616 BC, Nabopolassar had united the entire area under his rule.
Nabopolassar formed an alliance with Cyaxares of the Medes to confront the Assyrians and their Egyptian allies. By 615 BC he had seized Nippur. He then led his forces to assist the Medes besieging the city of Ashur, but the Babylonian army did not reach the battlefield until after the city had fallen.