What was true of darius's coup 522 bce?

The Persian Empire was founded by Cyrus the great and when he died, his son Cambyses succeeded him. Like his father, he also conquer new countries to his empire. When Cambyses went to Egypt, the people became hostile and a man who name himself Smerdis whom he claim that he is the son of Cyrus and brother of Cambyses led the empire but the people revolt against him for they know that this man lied to them.

Meanwhile, the cause of death of Cambyses is not clear. During the revolution, a conspiracy was believed to overthrown the false king through the leadership of Darius who is a distant relative of Cambyses and initiated the coup against Smerdis.

Moreover, it was also mention that Darius was the one who killed the false king and after several debate, Darius was accepted as the king of ancient Persia, whose reign lasted from 522 to 486 bce.

accelerated heartbeat, raise in blood pressure, slow in digestion, raise in blood sugar and perspiration. (myers' psychology for ap 2nd edition pg 87)