Cambyses II was the son of Cyrus the Great and King of Persia from 530 BCE to 522 BCE.
It was quite natural that, after Cyrus had conquered the Middle East, Cambyses should undertake the conquest of Egypt, the only remaining independent state in that part of the world. Before he set out on his expedition, he killed his brother Bardiya (Smerdis), whom Cyrus had appointed governor of the eastern provinces.
In the decisive battle at Pelusium the Egyptian army was defeated, and shortly afterwards Memphis was taken. The captive king Psammetichus was executed, having attempted a rebellion. The Egyptian inscriptions show that Cambyses officially adopted the titles and the costume of the Pharaohs.
His forces invaded the Kingdom of Kush without any breakthrough successes. Another expedition against the Siwa Oasis failed likewise. Cambyses II's plan of attacking Carthage was frustrated by the refusal of the Phoenicians to operate against their kindred.
According to Herodotus 3.26, Cambyses sent an army to threaten the Oracle of Amun at the Siwa Oasis. The army of 50,000 men was halfway across the desert when a massive sandstorm sprang up, burying them all.
Meanwhile in Persia a man was trying to steal the throne, he shared the same name as Cambyses' brother, Smerdis, although it was later claimed by Darius, after he had killed him and claimed the throne for himself, that this was not in fact the genuine Smerdis but an impostor, a Magian named Gaumata, Smerdis having been murdered some three years previously. According to his successor Darius, Cambyses felt that victory was impossible and committed suicide. According to Herodotus, he died of an injury while mounting his horse on the way back to Persia.