The Third Intermediate Period of ancient Egypt began with the death of Pharaoh Ramesses XI in 1077 BC. Which ended the New Kingdom, and eventually followed by the Late Period. Various points offered as the beginning for the latter era. Though it is most often regarded as dating from the foundation of the Twenty-Sixth Dynasty by Psamtik I in 664 BC, following the departure of the Nubian Kushite rulers of the Twenty-fifth Dynasty after they were driven out by the Assyrians under King Ashurbanipal.
The use of the term “Third Intermediate Period”, based on the analogy of the well-known First and Second Intermediate Periods. It was popular by 1978, when British Egyptologist Kenneth Kitchen used the term for the title of his book on the period. While Kitchen argued that the period was ‘far from being chaotic’ and hoped that his work would lead to the abolishment of the term, with his own preference being the ‘Post-Imperial epoch’, his use of the term as a title seems only to have entrenched the use of the term.
The period ruled by non-native Egyptians. In addition to, viewed as one of decline and political instability including division of the state, coinciding with the Late Bronze Age collapse of civilizations in the ancient Near East and Eastern Mediterranean (including the Greek Dark Ages).
End of the Third Intermediate Period
Upper Egypt remained for a time under the rule of Taharqa and Tantamani. Whilst Lower Egypt ruled from 664 BC by the nascent 26th Dynasty. Client kings established by the Assyrians. In 663 BC, Tantamani launched a full-scale invasion of Lower Egypt, taking Memphis in April of this year, killing Necho I of Sais in the process as Necho had remained loyal to Ashurbanipal.
Tantamani barely had the time to receive the submission of some Delta kinglets and expel the remaining Assyrians that a large army led by Ashurbanipal and Necho’s son Psamtik I came back. Tantamani was defeated north of Memphis and Thebes was thoroughly sacked shortly after. The Kushite king withdrew to Nubia while the Assyrian influence in Upper Egypt quickly waned.
Permanently weakened by the sack, Thebes peacefully submitted itself to Psamtik’s fleet in 656 BC. To affirm his authority, Psamtik placed his daughter in position to be the future Divine Adoratrice of Amun. Thereby also submitting the priesthood of Amun and effectively uniting Egypt. Tantamani’s successor Atlanersa was in no position to attempt a reconquest of Egypt as Psamtik. Also secured the southern border at Elephantine and may even have sent a military campaign to Napata. Concurrently, Psamtik managed to free himself from the Assyrian vassalage while remaining on good terms with Ashurbanipal. Possibly owing to an ongoing rebellion in Babylon. By doing so, he brought increased stability to the country during his 54-year reign from the city of Sais beginning the Late Period of ancient Egypt