Mesopotamia was conquered by the Achaemenid Persians under Cyrus the Great in 539 BCE, and remained under Persian rule for two centuries. For two centuries of Achaemenid rule both Assyria and Babylonia flourished, Achaemenid Assyria in particular becoming a major source of manpower for the army and a breadbasket for the economy. Mesopotamian Aramaic remained the lingua franca of the Achaemenid Empire, much as it had done in Assyrian times. The Achaemenid Persians, unlike the Neo-Assyrians, minimally interfered in the internal affairs of their territories, focusing instead on the consistent flow of tribute and taxes.^[40]

Athura, known as Assyria in the Achaemenid Empire, was a region in Upper Mesopotamia from 539 to 330 BCE. It functioned as a military protectorate rather than a traditional satrapy. Achaemenid inscriptions describe Athura as a 'dahyu,' interpreted as a group of people or a country and its people, without administrative implications.^[41] Athura encompassed most of the former Neo-Assyrian Empire territories, now parts of northern Iraq, northwestern Iran, northeastern Syria, and southeast Anatolia, but excluded Egypt and the Sinai Peninsula.^[42] Assyrian soldiers were prominent in the Achaemenid military as heavy infantry.^[43] Despite initial devastations, Athura was a prosperous region, especially in agriculture, contradicting earlier beliefs of it being a wasteland.^[42]