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.
From c. 665–664 BC, Taharqa and Tantamani had lost control of Lower Egypt, which came under the power of Assyrian vassals 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.
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.
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.
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.

Despite these developments, Atlanersa adopted the fivefold titulary in the style of Egyptian pharaohs; gave himself the epithets of "Son of Ra" and "King of Upper and Lower Egypt" in his inscriptions; and had the gods promise him lordship over Egypt in exchange for Temple B700.

While Atlanersa's Horus name, "Founder of the two lands", is identical with that of the much earlier king of the 13th Dynasty, Neferhotep I, Török proposes that it is rather based on the titles of Theban kings of the Third Intermediate Period.
For example, starting with the High-priest of Amun Herihor (fl.
 c. 1080 BC), a number of rulers of the 21st and 22nd Dynasties were called "son of Amun whom he placed on his throne to be founder of the Two Lands", a prominent example being Osorkon I (fl.
 c. 900 BC).
In the same vein, Atlanersa's nebty name of "Mery Maat" was also borne by the kings Siamun (fl.
 c. 970 BC), Osorkon II (fl.
c. 850 BC) and Shoshenq III (fl.
 c. 810 BC).

Serge Sauneron and Jean Yoyotte proposed that either Atlanersa or Senkamanisken faced an incursion of Egyptian troops under the command of  Psamtik I, who very probably also established a garrison on Elephantine to guard the border.
This hypothesis is contested by Török, who points to the lack of direct evidence.
In any case, a raid on Napata by the Egyptians did take place during the later reign of Psamtik II c. 593 BC.
During this raid, the colossal statue of Atlanersa in front of Temple B700 was toppled and its head cut off.
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. From c. 665–664 BC, Taharqa and Tantamani had lost control of Lower Egypt, which came under the power of Assyrian vassals 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. 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. 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. 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.
Despite these developments, Atlanersa adopted the fivefold titulary in the style of Egyptian pharaohs; gave himself the epithets of "Son of Ra" and "King of Upper and Lower Egypt" in his inscriptions; and had the gods promise him lordship over Egypt in exchange for Temple B700.
While Atlanersa's Horus name, "Founder of the two lands", is identical with that of the much earlier king of the 13th Dynasty, Neferhotep I, Török proposes that it is rather based on the titles of Theban kings of the Third Intermediate Period. For example, starting with the High-priest of Amun Herihor (fl. c. 1080 BC), a number of rulers of the 21st and 22nd Dynasties were called "son of Amun whom he placed on his throne to be founder of the Two Lands", a prominent example being Osorkon I (fl. c. 900 BC). In the same vein, Atlanersa's nebty name of "Mery Maat" was also borne by the kings Siamun (fl. c. 970 BC), Osorkon II (fl. c. 850 BC) and Shoshenq III (fl. c. 810 BC).
Serge Sauneron and Jean Yoyotte proposed that either Atlanersa or Senkamanisken faced an incursion of Egyptian troops under the command of  Psamtik I, who very probably also established a garrison on Elephantine to guard the border. This hypothesis is contested by Török, who points to the lack of direct evidence. In any case, a raid on Napata by the Egyptians did take place during the later reign of Psamtik II c. 593 BC. During this raid, the colossal statue of Atlanersa in front of Temple B700 was toppled and its head cut off.
Atlanersa