Once the Assyrians had appointed Necho I as king and left Egypt, Tanwetamani marched down the Nile from Nubia and reoccupied all of Egypt including Memphis. Necho I, the Assyrians' representative, was killed in Tanwetamani's campaign. He became King of Egypt for 7 years. In reaction, the Assyrians returned to Egypt in force, defeated Tanwetamani's army in the Delta and advanced as far as south as Thebes, which they sacked. The Assyrian reconquest effectively ended Nubian control over Egypt although Tanwetamani's authority was still recognized in Upper Egypt until his 8th Year in 656 BC when Psamtik I's navy peacefully took control of Thebes and effectively unified all of Egypt.
Kushite King Tanwetamani
664-656 B.C., 25th Dynasty Egypt
Photo from the book The Nubian Pharaohs: Black Kings of the Nile, by Bonnet & Valbelle (2007)