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.

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.

In the last two centuries or so of Parthian rule, Assyria flourished; the great cities of old, such as Assur, Nineveh and Nimrud were resettled and expanded, old villages rebuilt and new settlements constructed.

This latter-day Assyrian cultural golden age came to an end when Ardashir I of the Sasanian Empire overthrew the Parthians and, during his campaigns against them, extensively sacked Assyria and its cities.

[3] Archaeological surveys of northern Mesopotamia have consistently shown that there was a dramatic decrease in the size and number of inhabited sites in Assyria during the Neo-Babylonian period, suggesting a significant societal breakdown in the region.

[11] Individuals with Assyrian names are attested at multiple sites in Babylonia during the Neo-Babylonian Empire, including Babylon, Nippur, Uruk, Sippar, Dilbat and Borsippa.

[3] At some point after the fall of Nineveh in 612 BC some of the faces in the reliefs of its palaces were destroyed, but there is no evidence for longer Babylonian or Median occupation of the site.

Two Neo-Babylonian texts discovered at the city of Sippar in Babylonia attest to there being royally appointed governors at both Assur and Guzana, another Assyrian site in the north.

[14] The Persians first entered Assyrian territory in 547 BC, when the founder of the Achaemenid Empire, Cyrus the Great, crossed the Tigris river and marched south of Arbela while campaigning against the Medes.

[17][20] The organization of most of Assyria into the single administrative unit Athura effectively kept the region on the map as a distinct political entity throughout the time of Achaemenid rule.

[21] The Achaemenid kings interfered little with the internal affairs of their individual provinces as long as tribute and taxes were continuously provided, which allowed Assyrian culture and customs to survive under Persian rule.

An Aramaic letter sent by the governor of Egypt in the late 5th century BC attests to the presence of Achaemenid officials at the cities of Arbela, Lair, Arzuhin and Matalubaš, which suggests that there was a certain level of administrative organization in the region.

At Tell ed-Daim, located on the Little Zab northeast of Kirkuk, an Achaemenid administrative building of substantial size (26 by 22 meters; 85 by 72 feet), probably a palace of a local governor or official, has been excavated.

[21] A few years after the Egyptian governor's letter, Xenophon, a Greek military leader and historian, marched with the Ten Thousand through much of the northwestern Achaemenid Empire, including Assyria, in 401 BC.

In 520 BC, Assyrians of both Athura and Media joined forces in an unsuccessful revolt against Darius, alongside other peoples of the Achaemenid Empire (including the Medes, Elamites and Babylonians).

[10] Though Assyria was centrally located within this empire, and must have been a significant base of power,[10][24] the region is mentioned very rarely in textual sources from the period.

[29] A few exceptions to the sequences of non-native rulers also existed; the name of the earliest known king of Adiabene, Abdissares, is clearly of Aramaic origin and means "servant of Ishtar".

[31] Because of scarcity of documentation and the region often being politically unstable, the precise boundaries and political status of many locations is not entirely clear throughout the Parthian period; minor Armenian principalities in the highlands and mountains in far northern Mesopotamia established in the Seleucid period, such as Sophene, Zabdicene, Corduene, may have also preserved some independence or autonomy in Parthian times.

Helped by favorable climate conditions and political stability, this age of recovery culminated in an unprecedented return to prosperity and a remarkable revival under the last two centuries or so of Parthian rule.

Archaeological surveys of sites of the Parthian period in Assyria demonstrate an enormous density of settlements that is only comparable to what the region was like under the Neo-Assyrian Empire.

[26] The Seleucid and Parthian resettlement of Nineveh involved the construction of both residential houses and new sanctuaries and temples, with archaeological evidence having survived of both.

An inscription is preserved from this temple, dated to Parthian rule in 32/31 BC, by a Greek worshipper named Apollophanes, who dedicated it to the strategos[f] of Nineveh, Apollonios.

Archaeological evidence shows that the throne room of the former Southwest Palace, built by the Assyrian king Sennacherib, was converted into a religious sanctuary dedicated to Heracles.

[35] Called Ninos in Greek,[29] Nineveh was for most of the Parthian period under the control of Adiabene and though not a great political center, the city retained its local importance as a market-settlement along the Tigris river throughout this time.

[23] Nineveh was relatively Hellenized, with its population worshipping syncretistic Greco-Mesopotamian deities[36] and many being able to speak Greek,[37] but the predominant language in the city and in the surrounding countryside likely remained Aramaic.

[43] Evidence of squatter occupation of some sites has been uncovered, such as scant archaeological finds indicating repair-work and the construction of small houses and workshops at Nimrud, Dur-Sharrukin and Assur in the Neo-Babylonian and Achaemenid periods.

[52] Most of the archaeological finds from Seleucid and Parthian Nineveh are from the Kuyunjik mound,[53] with knowledge of much of the lower city itself only deriving from a small number of chance discoveries.

[59] Though outside Assyria proper, excavations of the Parthian-age sections of the nearby site Dura-Europos found a temple with a diverse arrangement of deities, a Christian church and a Jewish synagogue, all dating to the 3rd century AD.

[32][60] One of the temples built in the Parthian period included in its cult room a stele with a high relief depicting the demigod Heracles with a lion's skin over his left arm and resting his right hand on a club.