Cambyses II (Persian Kambujiya), was the name borne by the father and the son of Cyrus the Great.
When Cyrus conquered Babylon in 539 BC he was employed in leading religious ceremonies (Chronicle of Nabonidus), and in the cylinder which contains Cyrus's proclamation to the Babylonians his name is joined to that of his father in the prayers to Marduk. On a tablet dated from the first year of Cyrus, Cambyses is called king of Babel. But his authority seems to have been quite ephemeral; it was only in 530 BC, when Cyrus set out on his last expedition into the East, that he associated Cambyses on the throne, and numerous Babylonian tablets of this time are dated from the accession and the first year of Cambyses, when Cyrus was "king of the countries" (i.e. of the world). After the death of his father in the spring of 528 BC, Cambyses became sole king. The tablets dated from his reign in Babylonia run to the end of his eighth year, i.e. March 521 BC. Herodotus (3. 66), who dates his reign from the death of Cyrus, gives him seven years five months, i.e. from 528 to the summer of 521. For these dates cf. Ed. Meyer, Forschungen zur alten Geschichte, ii. 470ff.
The traditions about Cambyses, preserved by the Greek authors, come from two different sources. The first, which forms the main part of the account of Herodotus (3. 2-4; 10-37), is of Egyptian origin. Here Cambyses is made the legitimate son of Cyrus and a daughter of Apries named Nitetis (Herod. 3.2, Dinon fr. II, Polyaen. viii. 29), whose death he avenges on the successor of the usurper Amasis. (In Herod. 3.1 and Ctesias a/i. Athen. Xiii. 560), this tradition is corrected by the Persians:
Cambyses wants to marry a daughter of Amasis, who sends him a daughter of Apries instead of his own daughter, and by her Cambyses is induced to begin the war. His great crime is the killing of the Apis, for which he is punished by madness, in which he commits many other crimes, kills his brother and his sister, and at last loses his empire and dies from a wound in the hip, at the same place where he had wounded the sacred animal. Intermingled are some stories derived from the Greek mercenaries, especially about their leader Phanes of Halicarnassus, who betrayed Egypt to the Persians. In the Persian tradition the crime of Cambyses is the murder of his brother; he is further accused of drunkenness, in which he commits many crimes, and thus accelerates his ruin. These traditions are found in different passages of Herodotus, and in a later form, but with some trustworthy detail about his household, in the fragments of Ctesias. With the exception of Babylonian dated tablets and some Egyptian inscriptions, we possess no contemporary evidence about the reign of Cambyses but the short account of Darius in the Behistun Inscription. It is impossible from these sources to form a correct picture of Cambyses' character; but it seems certain that he was a wild despot and that he was led by drunkenness to many atrocious deeds.
It was quite natural that, after Cyrus had conquered Asia, Cambyses should undertake the conquest of Egypt, the only remaining independent state of the Eastern world. Before he set out on his expedition he killed his brother Bardiya (Smerdis), whom Cyrus had appointed governor of the eastern provinces. The date is given by Darius, whereas the Greek authors narrate the murder after the conquest of Egypt. The war took place in 525, when. Amasis had just been succeeded by his son Psammetichus III. Cambyses had prepared for the march through the desert by an alliance with Arabian chieftains, who brought a large supply of water to the stations. King Amasis had hoped that Egypt would be able to withstand the threatened Persian attack by an alliance with the Greeks. But this hope failed; the Cypriot towns and the tyrant Polycrates of Samos, who possessed a large fleet, now preferred to join the Persians, and the commander of the Greek troops, Phanes of Halicarnassus, went over to them. In the decisive battle at Pelusium the Egyptians were beaten, 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, although we may very well believe that he did not conceal his contempt for the customs and the religion of the Egyptians. From Egypt Cambyses attempted the conquest of Kush, i.e. the kingdoms of Napata and Meroe, located in the modern Sudan. But his army was not able to cross the deserts; after heavy losses he was forced to return. In an inscription from Napata (in the Berlin museum) the Nubian king Nastesen relates that he had beaten the troops of Kembasuden, i.e. Cambyses, and taken all his ships (H. Schafer, Die Aethiopische Königsinschrift des Berliner Museums, 1901). Another expedition against the Siwa Oasis failed likewise, and the plan of attacking Carthage was frustrated by the refusal of the Phoenicians to operate against their kindred. Meanwhile in Persia a usurper, the Magian Gaumata, arose in the spring of 522, who pretended to be the murdered Bardiya (Smerdis), who was acknowledged throughout Asia. Cambyses attempted to march against him, but, seeing probably that success was impossible, died by his own hand (March 521). This is the account of Darius, which certainly must be preferred to the traditions of Herodotus and Ctesias, which ascribe his death to an accident. According to Herodotus (3.64) he died in the Syrian Ecbatana, i.e. Hamath; Josephus (Antiquites xi. 2. 2) names Damascus; Ctesias, Babylon, which is absolutely impossible.
See A. Lincke, "Kambyses in der Sage, Litteratur und Kunst des Mittelalters", in Aegyptiaca: Festschrift für Georg Ebers (Leipzig 1897), pp. 41-61; also History of Persia.
The Lost Army Of Cambyses
According to Herodotus, 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 sprung up burying them all. Although many Egyptologists regard the story as a myth, people have searched for the remains for many years. These have included Count Lazlo de Almásy (on whom the novel The English Patient was based) and modern geologist Tom Brown. Some believe recent petroleum excavations may have uncovered remains of the army.  (http://touregypt.net/featurestories/cambyses2.htm) A 2002 novel by Paul Sussman The Lost Army Of Cambyses (ISBN 0593048768) recounts the story of rival archaeological expeditions searching for the remains.