Assyria's recovery as a great power in the reign of Adad-nirari II (912-891 BC) heralded the beginning of an empire which was destined to sweep away the old *Hittite supremacy and to encompass the Nile valley.
Great Assyrian rulers such as *Tiglath-pileser III and *Sennacherib came into conflict with Egypt over the small states in Syria/Palestine. Finally, *Esarhaddon took the fight into Egypt and drove the Ethiopian ruler *Taharka (whose dynasty now ruled Egypt) back to the south; although he returned briefly to Egypt, a later Assyrian king, *Ashurbanipal, again forced him back to his southern kingdom.
Under *Ashurbanipal, the Assyrian empire was at its height, and he was able to establish his supremacy in Egypt, sacking Thebes in 664 BC and carrying booty back to Nineveh. Troubles at home forced him to return to Assyria and he left *Necho, a prince of the city of Sais, in charge of Egypt. One of *Necho's successors, *Psammetichus I, was able to consolidate the position of the Saite princes as kings of the Twenty-sixth Dynasty, by using foreign mercenaries to establish his supremacy over the other native princes.
The Assyrians never returned to Egypt, but the new and dangerous alliance of the Babylonians and the Medes persuaded the Egyptians to ally with Assyria in 616 BC. However, the Babylonians sacked Nineveh, capital of Assyria, in 612 BC, and became the new threat for Egypt.
In the ninth century BC, the Assyrian kings had succeeded in establishing the greatest empire the world had yet seen; it was based on a constitution as a nation rather than incoporating a collection of client city-states (as earlier empires had been) and it was supported by an advanced army which possessed sophisticated weapons and which relied on compulsory military service.
BIBL. Von Zeissl, H. Athiopen und Assyrer in Agypten. Gluckstadt: 1944; Pritchard, J.B. (Ed.) ANET. Princeton, 1969.
Biographical Dictionary of Ancient Egypt by Rosalie and Antony E. David
Ancient Egypt. A Reference Guide. EdwART. 2011.