This alternate history looks at the possibility that ancient Egypt wasn’t conquered.
From an earlier period in time, after the Middle Kingdom, the Hyksos conquered the northern parts of Egypt, but the Sixteenth and Seventeenth Dynasties based in Thebes continued to exist. In the last Seventeenth Dynasty, Seqenenra Taa and Kamose fought against the Hyksos and Ahmose I, who started the Eighteenth Dynasty and the New Kingdom, drove the Hyksos out of Egypt.
The Late Period of ancient Egypt started around 653 B.C.E.. In 525 B.C.E..
The Egyptians were in the midst of a civil war, with self-styled monarchs who ruled from Herakleopolis, Tanis, Hermaopolis, Thebes, Memphis, and Sais. This civil war allowed a Nubian invasion from the south. The 24th and 25th Dynasties were under Nubian rule.
Assyrian invasions caused Egypt to unite. The Assyrians conquered Egypt under Easrhaddon in 671 and 670 B.C.E.. The Assyrians were driven out, but reconquered Egypt under Ashurbanipal in 666 B.C.E.. Again, the Assyrians were driven out. Psamtik II allied with the Greeks to oust the Assyrians.
The 26th Dynasty was called the Saite Period because the capital was Sais.
Psamtik II and later Pharaohs re-established old traditions, including building great monumnets to Pharaoh and the divine. They successfully fought off foreign invasions by the Babylonians.
Pharaoh Ahmose II based his rule on a renewed sense of Egyptian nationalism. He expected the Persians to attempt an invasion, so he hired Greek mercenaries to prepare, but died before the war.
His son, Pharaoh Psamtik III, confidently moved the army to Pelsium, a well supplied and defended fortress.
In 525 B.C.E. Persian King Cambyses II invaded Egyt, winning the Battle of Pelusium, beginning the Achaemenid Period of Egypt, the 27th Dynasty, and creating the largest empire in the world at that time.
Cambyses II of Persia was aided by 40 triremes from Polycrates of Samos. Phanos, a Greek mercenary general who served under Psmatik III’s father, betrayed Psmatik and provided Cambyses II with vital military information. Arabs provided Cambyses’s army with water for the crossing of the Sinai Desert in 525 B.C.E..
After a frustrating campaign, Cambyses II switched to psychological warfare. He had depictions of cats put on Persian shields and drove sacred animals before his army. The Egyptians refused to fight against symbols of their own religion and were routed.
After the battle of Pelusium in the Nile Delta, the Egyptians retreated to Memphis. The Persians captured Helopolis and then besieged Memphis. The city and Psamtik III were captured. The Pharaoh was held in captivity at Susa.
Cambyses attempt to conquer Carthage failed when his Phoenician sailors refused to attack the colony. Cambyses sent an army to conquer Egyptian holdouts at the Oasis of Amon, but it was lost in a sand storm. Cambyses led an army into Nubia, but after some initial success he withdrew because of a lack of supplies.
Cambyses set up garrisons at Daphnae, Memphis, and Elephantine. In 522 B.C.E. a revolt led by his brother Bardiya broke out in the Persian homeland. Cambyses died on the return home. Darius I took command of Persia.
The Egyptian province (First Egyptian Satrapy) was troublesome and the Egyptians successfully revolted in 486 B.C.E.. Egypt was reconquered in 485 B.C.E.. A second revolt started in 459 B.C.E. and continued until 454 B.C.E.. A third revolt occurred in 405 B.C.E. and the Egyptians fought off several Persian conquest attempts, remaining independent until 343 B.C.E.. A final revolt was crushed in 337-336 B.C.E.. Alexander the Great overthrew Darius III, the last Achaemenid emperor and this started the Hellenic period of ancient Egypt.
We will assume that the third revolt resulted in Egypt being restored to its former power.