Early attempts by Parthian rulers to take Babylon were short-lived, but in 141 BC they established their kingship by celebrating the New Year festival. Chronicles and astronomical diaries continued to be written. An independent ruler of Maysan in the Sealand, Hyspaosines, captured the port on the Tigris, took control of Bahrain and Failaka to control Gulf trade, and briefly claimed kingship of Babylon. He wrote in Aramaic. The Parthians regained control and rebuilt the Greek theatre. The old buildings and city plan continued to be in use, although the Summer Palace had been reroofed with terracotta tiles. New kinds of text were written on clay in cuneiform, astronomical science developed; an archive shows that temples were still active, and much older literature was still prized. Greek knowledge of the Epic of Creation was still alive in Athens from the time of Alexander until the sixth century AD. The cult of Bēl had spread west to Palmyra, to the Aegean island of Kos, and north to Edessa. In AD 116 Trajan visited the Summer Palace on a pilgrimage to the place where Alexander had died.

Relations with Assyria dominated from the tenth to the late seventh century. Marduk’s reputation was tarnished as Babylon lost power. Tribes of Chaldeans and Arameans moved into the Sealand, where some settled, becoming literate and powerful. Iron gradually replaced bronze. Fine stone carving continued. Warlike Assyrian kings venerated Babylon, incorporated its gods into their pantheon, and treated the city separately from the rest of Babylonia; but Assyria and Babylon clashed east of the Tigris at Der. Chaldeans intermittently took the throne. Tiglath-pileser III, the first Assyrian king to become king of Babylon, took part in the New Year festival; Sargon II, the second, deposed a Chaldean and deported many disloyal groups, but invested in the city. When Sennacherib ruled Assyria, various rulers of Babylon and interference from Elam ended when he sacked Babylon, which remained kingless for seven years. His patricidal son Esarhaddon made some restitution. At his early death, Esarhaddon’s elder son took the throne, dominated by his younger son, Ashurbanipal, whose library at Nineveh included many Babylonian texts. Betrayed by his brother under Elamite influence, Ashurbanipal sacked Babylon. Royal records end, and three subsequent kings are poorly attested. Nabopolassar, a Babylonian general working in the Assyrian army, defected and took the throne of Babylon.

Nabopolassar fought with an Assyrian-style army and took the throne of Babylon. Thirteen years later, Nineveh fell despite Egyptian help. Babylon took over much of the Assyrian empire. Later he defeated the last Assyrian king at Harran. His success was seen as Marduk’s revenge. Captured wealth from Assyrian royal cities allowed major building work at Babylon, which was continued by Nabopolassar’s son Nebuchadnezzar II. Neither king left statues of themselves, and cylinder seals represent gods by their symbols. Major subsidence in the citadel required frequent rebuilding on the Southern Palace. The names of temples and gates were compiled on to a clay tablet as a literary work. Colour-glazed bricks adorned the Processional Way leading to the temple of the New Year festival outside the citadel walls. That festival is described. Some of his creations Nebuchadnezzar described as a Wonder, but he made no mention of the Hanging Garden. In a separate part of the citadel, Nebuchadnezzar built a Summer Palace. His conquests included Tyre and Ashkelon but not Egypt or Lydia. He sacked the Temple in Jerusalem and deported its royal family to Babylon. Other captives settled on land nearby. Business archives of long duration continue into the Achaemenid period.