Athura (𐎠𐎰𐎢𐎼𐎠 Aθurā), also called Assyria, was a geographical area within the Achaemenid Empire in Upper Mesopotamia from 539 to 330 BC as a military protectorate state. Although sometimes regarded as a satrapy, Achaemenid royal inscriptions list it as a dahyu (plural dahyāva), a concept generally interpreted as meaning either a group of people or both a country and its people, without any administrative implication.
It mostly incorporated the territories of Neo-Assyrian Empire corresponding to what is now northern Iraq in the upper Tigris, the middle and upper Euphrates, parts of modern-day northwestern Iran, modern-day northeastern Syria (Eber-Nari) and part of southeast Anatolia (now Turkey). However, Egypt and the Sinai Peninsula were separate Achaemenid territories. The Neo-Assyrian Empire collapsed after a period of violent civil wars, followed by an invasion by a coalition of some of its former subject peoples, the Iranian peoples (Medes, Persians and Scythians), Babylonians and Cimmerians in the late seventh century BC, culminating in the Battle of Nineveh, and Assyria had fallen completely by 609 BC.
Between 609 and 559 BC, former Assyrian territories were divided between the Median Empire to the east and the Neo-Babylonian Empire to the west. Both parts were subsumed into the Achaemenid Empire in 539 BC, and it has been argued that they constituted the satrapies of Media and Aθurā, respectively. In Herodotus' account, the Ninth Tributary District comprised "Babylonia and the rest of Assyria" and excluded Eber-Nari.
Despite a few rebellions, Aθurā functioned as an important part of the Achaemenid Empire and its inhabitants were given the right to govern themselves throughout Achaemenid rule and Old Aramaic was used diplomatically by the Achaemenids.
Known for their combat skills, Assyrian soldiers (along with the Lydians) constituted the main heavy infantry of the Achaemenid military. Due to the major destruction of Assyria during the fall of its empire, some early scholars described the area as an "uninhabited wasteland.