Darius I

On September 29, 522 BC, Darius I of Persia killed the usurper Gaumâta thus securing his hold as King of the Persian Empire. An excerpt from the article:

"The false king's reign did not last long. Herodotus tells us that Phaedymia, the daughter of Cambyses' uncle, Otanes, found out that the ruler is not Cambyses' brother. Her father, after learning the truth, quickly assembled a group of conspirators which included Hydarnes, Intaphrenes, Megabyzus, and Darius, who at the time was still the king's lancer. Gaumata was finally assassinated, leaving the Persian empire without a leader; the conspirators had to decide the future of the empire. Otanes opted out, wanting only special privileges for his family, oligarchy was suggested by Megabyzus, while Darius voted for a monarchy. Being unable to settle the matter at hand, all of them agreed on a contest, where the winner would take the throne. All of them would meet the next morning, each on his horse, and the first horse to neigh at the sunrise would be named the new king. Herodotus tells us that Darius cheated; supposedly it was his servant, Oebares, who made the horse neigh by letting the animal smell his hand that he had previously rubbed over the genitals of a mare. In any case, the horse's neigh accompanied by lightning and thunder from a storm convinced the others to accept Darius as the new king in 522 BCE.

Even though Gaumata was a false ruler, only a portion of satrapies recognised Darius as their king, after his coronation, in 522 BCE, such as Bactria and Arachosia. Others saw the false king's death as a chance for independence. Revolts broke out across many regions of the empire, including Persis, Media, Parthia, Assyria, Babylon, and Egypt, and only with aid of his army and personal entourage did Darius manage to quell these conflicts. These events are chronicled in great detail in his inscriptions, translated by Herbert Cushing, which also serve as a warning for future kings:

Says Darius the king: O thou who shalt be king in
the future, protect thyself strongly from Deceit;
whatever man shall be a deceiver, him who deserves
to be punished, punish, if thus thou shalt think " may
my country be secure." (30)

[...]
Says Darius the king: O thou who shalt be
king in the future, whatever man shall be a deceiver
or a wrong-doer (be) not a friend to these; punish
(them) with severe punishment. (33)."