By the end of Taharqa's reign, the 25th Dynasty state was in crisis, on the losing side of a war against the Neo-Assyrian Empire.[79] From c. 665–664 BC, Taharqa and Tantamani had lost control of Lower Egypt, which came under the power of Assyrian vassals[note 9] including Necho I and his son in Sais, the future great pharaoh Psamtik I. In 663 BC, Tantamani managed a short-lived reconquest of Memphis, killing Necho I in the process, but was beaten during the ensuing campaign by Ashurbanipal, which finished with the sack of Thebes that same year.[81] Weakened, the Kushites could not resist the subsequent rise of the Twenty-sixth Dynasty of Egypt under the impulse of Psamtik I, who proceeded south quickly during the remainder of Tantamani's reign, definitively expelling him from Upper Egypt c. 656 BC.[10] Thus, in contrast to his predecessors, Atlanersa's kingdom was restricted to the region of Kush, south of Elephantine, and its seat of power was Napata.[82][83] The Kushites would nonetheless continue to wield a significant influence in the Theban region of Upper Egypt where an aristocracy of Nubian descent had established itself in the 8th century BC, in particular amongst the high clergy of Amun.[84]