When his brother, king Cambyses, was conquering Egypt (in 522), someone calling himself Smerdis rebelled and became sole ruler of the ancient Persian empire after Cambyses' death. According to the Behistun inscription, his rule started on March 11, 522, which is corroborated by the dating of letters in Babylonia; on July 1, he formally became king. The new king was killed, however, by Darius, on September 29 in a stronghold in Media. Darius states in the Behistun inscription that the man he now succeeded was not the real Smerdis -who he claims was killed before Cambyses set out for Egypt- and that the rebel was a lookalike named Gaumâta.
Later, a Persian named Vahyazdâta proclaimed himself king, also claiming to be the real Smerdis. He seized the Persian palace and was able to subdue Arachosia. But one of Darius' generals, Artavardiyâ, defeated this king on May 24, 521, after which he was forced to flee to the east. Vahyazdâta was defeated again on July 14 and crucified.
The picture shows Darius with the defeated Gaumâta at Behistun.
This author above agrees with historians who have mistaken the length of the reign of Smerdis. Smerdis, a fraud and usurper succeded Cambyses. This author in his sketch on Cambyses son of Cyrus accurately puts the death of Cambyses shortly (one or a very few years) after the death of Cyrus. Cyrus died in battle 5 years after he took Babylon in 536 BC so his death was about 531 BC. If Cambyses died a year or so later in 530 to 529 BC then Smerdis reigned more than one year. His reign was terminated by Darius I before 521 BC. His reign therefore was more likely between eight and nine years. The one year ascribed to Smerdis is due to a faulty reading of the Behistin inscription. FPM