Kassite Babylon eventually became subject to the Middle Assyrian Empire (1365–1053 BC) to the north, and Elam to the east, with both powers vying for control of the city. The Assyrian king Tukulti-Ninurta I took the throne of Babylon in 1235 BC.
Unfortunately, that son was evidently murdered before reaching his destination, and this alliance was never consummated. However, the Middle Assyrian Empire (1365–1050 BC) once more began to grow in power also, with the ascension of Ashur-uballit I in 1365 BC. Ashur-uballit I attacked and defeated Mattiwaza the Mitanni king despite attempts by the Hittite king Šuppiluliuma I, now fearful of growing Assyrian power, attempting to preserve his throne with military support. The lands of the Mitanni and Hurrians were duly appropriated by Assyria, enabling it to encroach on Hittite territory in eastern Asia Minor, and Adad-nirari I annexed Carchemish and northeast Syria from the control of the Hittites.
Ashur-uballit I (1365–1330 BC) went further, defeating Shuttarna III and bringing an end to the Mitanni empire, the Assyrian king then annexing its territories in Anatolia and the Levant, turning Assyria once more into a major empire. The ambitious Assyrian king went further still, attacking and conquering Babylonia, and imposing a puppet ruler loyal to himself upon its throne. Assyria then annexed hitherto Babylonian territory in central Mesopotamia.