Cambyses succeeded Cyrus II on the Persian throne in 525 BC, and one of his first acts was to march on Egypt, annihilating the Egyptian army at Pelusium. The king, Psametik III, was later taken prisoner and sent in chains to Susa, and unheard of humiliation for a King of Egypt.

Cambyses has generally had a critical reputation, largely as a result of Greek propaganda when the Persians' erstwhile allies became their enemies; he also incurred the enmity of the priests when he reduced the subsidies from the state to which certain of the temples had become accustomed. Certainly there is no clear evidence for his supposed sacrilegious slaughter of the sacred Apis Bull as tradition insists; rather he seems to have been concerned to respect Egyptian beliefs and customs, a posture which would have been in line with Persian policy overall. There is a stele which depicts him, in the full regalia of a king of Egypt, worshipping the Apis. He was also notorious, perhaps with greater justification, for the loss of an entire army and its treasure in a gigantic sandstorm when it was marching to Siwa.