After the death of Assurbanipal in 627 BC, the Neo-Assyrian empire entered a period of instability caused by fighting between Sin-shar-ishkun and his brother Assur-etil-ilani. In 626 BC, Nabopolassar, the Babylonian ruler revolted against the Assyrians. After a few years of war, the Babylonians expelled the Assyrian forces from their territory. However, Nabopolassar could not bring the fight to the heartland of the Assyrian empire. The situation changed drastically in 616 BC, when the Medes attacked the Assyrian empire.
The fall of Tarbiṣu occurred when the Median army, led by Cyaxares, attacked and conquered the city. In the aftermath, the Medes went further and decisively defeated the Assyrians at the battle of Assur.
^Who's Who in the Ancient Near East "It appears that Cyaxares did unite the Medes and achieved some impressive military victories. In 614 he attacked Nineveh and captured Ashur and Tarbisu"
^The Ancient Near East: History, Society and Economy "already by 614 BC, the Medes of Cyaxares (Umakishtar in the Babylonian chronicle) had invaded the Assyrian cities, conquering Tarbisu and then Ashur, which was brutally sacked"
