Assyria continued to prosper when Ashurbanipal, a younger son of Esarhaddon, became king (668–ca. 631 BC). During the second half of his reign, however, the kingdom began to suffer serious problems, not unlike those of the late ninth and early eighth centuries BC. By the time Ashurbanipal died, Assyrian might was declining. Assyria's fortunes continued to suffer under its next two kings, Aššur-etel-ilāni (ca. 630–627 BC) and Sîn-šarra-iškun (ca. 626–612 BC). In 612, the Babylonian king Nabopolassar and the Medes besieged the Assyrian capital Nineveh. Within three months, they captured and destroyed that city. In the northwest, Aššur-uballiṭ II (ca. 611–609 BC) declared himself king of Assyria in the city Ḫarrān. Even with support from Egypt, Aššur-uballiṭ was unable to maintain power. Military and political supremacy passed to Babylon in the south, under the control of Nabopolassar and his successors. Although Assyria ceased to exist as a political entity, much of its cultural and religious heritage endured.
Jamie Novotny
Jamie Novotny, 'Assyria from Ashurbanipal to Aššur-uballiṭ II (668–609 BC)', The Royal Inscriptions of the Neo-Assyrian Period, The RINAP Project, 2024 [http://oracc.museum.upenn.edu/rinap/Neo-AssyrianHistoryOverview/AssyriafromAshurbanipaltoAshur-uballitII668-609BC/]