During the fall of Assyria in the Medo-Babylonian conquest of the Assyrian Empire 626–609 BC, northern Mesopotamia was extensively sacked and destroyed by Median and Babylonian forces. The Babylonian kings, who annexed large parts of Assyria cared little for economically or socially developing the region and as such there was a dramatic decline in population density. Many of the greatest cities of the Neo-Assyrian period, such as Nineveh, were deserted and others, such as Assur, decreased dramatically in size and population. The region only began the process of recovery under the rule of the Achaemenid Empire. After his conquest of Babylon in 539, the Achaemenid king Cyrus the Great returned the cult statue of the Assyrian national deity Ashur to Assur. The Achaemenid practice of not interfering with local cultures, and the organization of the Assyrian lands into a single province, Athura, allowed Assyrian culture to endure.
