The revelation is contained in 22 lines of sophisticated hieroglyphics deciphered by Egyptologists from the British Museum and Egypt after their discovery in February in a richly decorated tomb at El Kab, near Thebes, in Upper Egypt.

Vivian Davies, Keeper of the museum’s Department of Ancient Egypt and Sudan, said: “In many ways this is the discovery of a lifetime, one that changes the textbooks. We’re absolutely staggered by it.”

The inscription details previously unknown important battles unprecedented “since the time of the god” — the beginning of time. Experts now believe that the humiliation of defeat was one that the Ancient Egyptians preferred to omit from their historical accounts.

Contemporary Egyptian descriptions had led historians to assume that the kingdom of Kush was a weak and barbaric neighbouring state for hundreds of years, although it boasted a complex society with vast resources of gold dominating the principal trade routes into the heart of Africa. It did eventually conquer Egypt, in the 8th century BC.

Mr Davies, who headed the joint British Museum and Egyptian archaeological team, said: “Now it is clear that Kush was a superpower which had the capacity to invade Egypt. It was a huge invasion, one that stirred up the entire region, a momentous event that is previously undocumented.

“They swept over the mountains, over the Nile, without limit. This is the first time we’ve got evidence. Far from Egypt being the supreme power of the Nile Valley, clearly Kush was at that time.

“Had they stayed to occupy Egypt, the Kushites might have eliminated it. That’s how close Egypt came to extinction. But the Egyptians were resilient enough to survive, and shortly afterwards inaugurated the great imperial age known as the New Kingdom. The Kushites weren’t interested in occupation. They went raiding for precious objects, a symbol of domination. They did a lot of damage.”

The inscription was found between two internal chambers in a rock-cut tomb that was covered in soot and dirt. It appeared gradually as the grime was removed.

Mr Davies said: “I thought it would be a religious text, but it turned out to be historical. Gradually, a real narrative emerged, a brand new text inscribed in red paint, reading from right to left.”

The tomb belonged to Sobeknakht, a Governor of El Kab, an important provincial capital during the latter part of the 17th Dynasty (about 1575-1550BC).

The inscription describes a ferocious invasion of Egypt by armies from Kush and its allies from the south, including the land of Punt, on the southern coast of the Red Sea. It says that vast territories were affected and describes Sobeknakht’s heroic role in organising a counter-attack.

The text takes the form of an address to the living by Sobeknakht: “Listen you, who are alive upon earth . . . Kush came . . . aroused along his length, he having stirred up the tribes of Wawat . . . the land of Punt and the Medjaw. . .” It describes the decisive role played by “the might of the great one, Nekhbet”, the vulture-goddess of El Kab, as “strong of heart against the Nubians, who were burnt through fire”, while the “chief of the nomads fell through the blast of her flame”.

The discovery explains why Egyptian treasures, including statues, stelae and an elegant alabaster vessel found in the royal tomb at Kerma, were buried in Kushite tombs: they were war trophies.

Mr Davies said: “That has never been properly explained before. Now it makes sense. It’s the key that unlocks the information. Now we know they were looted trophies, symbols of these kings’ power over the Egyptians. Each of the four main kings of Kush brought back looted treasures.”

The alabaster vessel is contemporary with the latter part of the 17th Dynasty. It bears a funerary text “for the spirit of the Governor, Hereditary Prince of Nekheb, Sobek- nakht”. Now it is clear that it was looted from Sobeknakht’s tomb, or an associated workshop, by the Kushite forces and taken back to Kerma, where it was buried in the precincts of the tomb of the Kushite king who had led or inspired the invasion.

The El Kab tomb was looted long ago, probably in antiquity. There is more to investigate at the enormous site and the Supreme Council of Antiquities in Egypt is now making such work a priority.

Rich pickings from ebony and ivory

Kush was a vast territory spanning modern-day northern Sudan. Ruled by kings who were buried with large quantities of luxury goods, including jewellery and inlaid furniture, it had complex political and religious institutions.

The economy was based on trading in ivory, ebony and incense, as well as slaves. Its skilled craftsmen left behind some of the finest ceramics produced in the ancient world.

The independent kingdom of Kush arose during the 8th century BC. The native kings laid claim to the Egyptian throne, declaring themselves the true heirs of Thutmose III and other great pharaonic ancestors. Under the leadership of King Piye (c747-716BC), they conquered Egypt, ruling as its 25th Dynasty.

The reign of King Taharqo (690-664BC) was a high point of the Kushite empire. He erected imposing temples, shrines and statues throughout the Nile Valley. His pyramid, the largest of the Kushite examples, soared to more than 48m (160ft).

Over 4,000 years interaction between the empires was inevitable. While they had different funerary practices at the time of the El Kab inscription — the Egyptians had tombs and pyramids while the Kushites preferred tumuli (grave mounds) — the Kushites went on to build pyramids and mummify their dead.

In return, the Egyptians were particularly influenced by Kushite jewellery design.

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