The Greek historian Herodotus, writing in the 5th century BCE, refers briefly to an Ethiopian war of Psamtik, an expedition that contemporary records prove to have been of great importance. Perhaps suspecting a Kushite threat to Egypt, Psamtik sent a large force against it. The army consisted of native Egyptians led by Amasis, who later became pharaoh, and mercenaries (Greeks, Phoenicians, and Jews) led by another general. A contemporary stela from Thebes dates the venture to the third year of Psamtik's reign and refers to a great defeat that was inflicted on a Kushite force. The expedition advanced at least as far south as the Third Cataract of the Nile River; Greek participants in the expedition left graffiti on the colossi at Abu Simbel, the temple of Ramses II, claiming to have advanced beyond Kerkis (perhaps modern Korkos) near the Fifth Cataract of the Nile, which stood well within the Kushite kingdom.

Psamtik initiated destruction of the memorials of the 25th (Kushite) dynasty in Egypt (see ancient Egypt: The 24th and 25th dynasties (Egypt, ancient)) by hacking out their names and the emblems of royalty from their statues and reliefs. Toward Palestine he apparently remained neutral. He paid a peaceful visit to Phoenicia in 591, after the Kushite campaign.