The third book opens with the invasion of Egypt by Cambyses in 525 on account of an insult offered him by Amasis. A Greek mercenary named Phanes gave the Persians information of the one means of attacking through the desert. After a fierce battle at Pelusium Egypt was beaten; for years afterwards skulls of both armies lay around, the Persian heads being easily broken by a pebble, the Egyptian scarcely breakable by stones. In victory Cambyses outraged Psammenitus, the defeated King; a fruitless expedition against Ethiopia and the Ammonians followed. The Egyptians were stirred by the arrival of their calf-god Apis; Cambyses mockingly wounded him and was punished with madness, slaying his own kindred and committing deeds of impiety. At that time Egypt was leagued with the powerful island of Samos, ruled by Polycrates, a tyrant of marvellous good fortune. Suspecting some coming disaster to balance it, Amasis urged him to sacrifice his dearest possession to avert the evil eye. Polycrates threw his ring into the sea; it was retrieved by a fisherman. On hearing this, Amasis severed his alliance. In the absence of Cambyses two Magi brothers stirred up revolt in Susa, one pretending to be Smerdis, the murdered brother of Cambyses. That monarch wounded himself in the thigh as he mounted his horse. The wound festered and caused speedy death. Meanwhile the false Smerdis held the sovereignty. He was suspected by Otanes, a noble whose daughter Phaedymé was married to him. At great personal risk she discovered that the King was without ears, a manifest proof that he was a Magian. Otane thens joined with six other conspirators to put the usurper down. Darius, son of Hystaspes, warned them that their numbers were too large for secrecy, advising immediate action. The two pretenders had meanwhile persuaded Prexaspes, a confidant of Cambyses, to assure the Persians that Smerdis really ruled. Prexaspes told the truth and then threw himself to death from the city walls. This news forced the conspirators' hands; rushing into the palace, they were luckily able to slay the usurpers. The next question was, who should reign? Herodotus turned these Persians into Greeks, making them discuss the comparative merits of monarchy, oligarchy and democracy. They decided that their horses should choose the next king; he whose steed should first neigh should rule. Darius had a cunning groom named Oebares; that evening he took the horse and his mare into the market-place; next morning on reaching the same spot the horse did not fail to seat his master on the throne in 521. A review of the Persian Empire follows, with a description of India and Arabia.