Darius I, known as Darius the Great, was the third "king of kings" (emperor) of the Achaemenid Empire. Darius held the empire at its peak, then
including Egypt, northern India, and parts of Greece. The decay and downfall of the empire commenced with his death and the coronation of his
son, Xerxes I.
Darius ascended the throne by assassinating the alleged usurper Bardiya with the assistance of six other Persian noble families; Darius was
crowned the following morning. The new emperor met with rebellions throughout his kingdom, and quelled them each time. A major event in
Darius's life was his expedition to punish Athens and Eretria for their aid in the Ionian Revolt and subjugate Greece. Darius expanded his
empire by conquering Thrace and Macedon, and invading the Saka, Iranian tribes who had invaded Medes and had previously killed Cyrus the Great.
Darius organized the empire, by dividing it into provinces and placing governors to govern it. He organized a new uniform monetary system,
along with making Aramaic the official language of the empire. Darius also worked on construction projects throughout the empire, focusing on
Susa, Pasargadae, Persepolis, Babylon, and Egypt. Darius created a codification of laws for Egypt. He also carved the cliff-face Behistun
Inscription, an autobiography of great modern linguistic significance.
See also: Behistun Inscription and Herodotus
Darius left a tri-lingual monumental relief on Mount Behistun which was written in Elamite, Old Persian and Babylonian between his coronation
and his death. The inscription first gives a brief autobiography of Darius with his ancestry and lineage. To expand on his ancestry, Darius
left a sequence of events that occurred after the death of Cyrus the Great. Darius mentions several times that he is the rightful emperor by
the grace of Ahura Mazda, the Zoroastrian God. In addition, further texts and monuments from Persepolis have been found, including a
fragmentary Old Iranian inscription from Gherla, Rumania (Harmatta), and a letter from Darius to Gadates, preserved in a Greek text of the
Roman period. 
Herodotus, a Greek historian and author of The Histories, provided an account of many Persian emperors and the Greco-Persian Wars. He wrote an
extensive amount of information on Darius which spans half of book 3, along with books 4, 5 and 6; it begins with removal of the alleged
usurper Gaumata and continues to the end of Darius's reign. 
The Book of Ezra (chapter 6, verse 1) describes the adoption and precise instructions to rebuild the Temple in Jerusalem. It was completed and
inaugurated of the sixth year of Darius (March 515 BCE), as also related in the Book of Ezra (chapter 6, verse 15), so the 70-year prophecy of
Jeremiah was fulfilled. Between Cyrus and Darius, an exchange of letters with King Ahasuerus and Artaxerxes is described (Chapter 4, Verse 7),
the grandson of Darius I, in whose reign Ezra and Nehemiah came to Jerusalem. The generous funding of the temple gave Darius and his successors
the support of the Jewish priesthood. There is mention of a Darius in the Book of Daniel, identified as Darius the Mede. He began ruling
when he was 62 years old (chapter 5, verse 31), appointed 120 satraps to govern over their provinces or districts (chapter 6, verse 1), was
made king over the realm of the Chaldeans (chapter 9, verse 1), and predated Cyrus (chapter 11, verse 1). Therefore, many scholars identify him
with Cyaxares II rather than Darius I of Persia.
Birth and youth -
Darius was born as the eldest son to Hystaspes and Rhodugune in 550 BCE. Hystaspes was a leading figure of authority in Persis which was the
homeland of the Persians. Darius' inscription states that his father was satrap of Bactria in 522 BCE. According to Herodotus, Hystaspes was
the satrap of Persis, although most historians state that this is an error. Also according to Herodotus (III.139), Darius, prior to seizing
power and "of no consequence at the time", had served as a spearman (doryphoros) in the Egyptian campaign (528–525 BCE) of Cambyses II, then
the Persian emperor.
Rise to power -
The rise of Darius to the throne contains two different sides to the story. Our sources (the Bisitun inscription and Herodotus) both give
similar stories (below). However, historians have inferred from these that Darius' rise to power may have been illegitimate. It seems likely
that 'Gaumata' was in fact Bardiya, and that under cover of revolts, Darius killed the heir to the throne and took it himself. The fact that
Darius' father and grandfather are still alive (Bisitun Inscription) implies that he was not the next in line to a hereditary throne.
Darius' version -
The account of Darius which is written at the Behistun Inscription states that Cambyses II killed his own brother Bardiya, but that this murder
was not known among the Iranian people. A would-be usurper named Gaumata came and lied to the people, stating he was Bardiya. The Iranians
had grown rebellious against Cambyses' rule, and on 11 March 522 BCE, a revolt against Cambyses broke out, in his absence.
On 1 July, the Iranian people chose to be under the leadership of Gaumata, as "Bardiya". No member of the Achamenid family would rise against
Gaumata for the safety of their own life. Darius, who had served Cambyses as his lance-bearer until the deposed ruler's death, prayed for aid,
and in September 522 BCE, he along with Otanes, Intraphrenes, Gobryas, Hydarnes, Megabyxus and Aspathines killed Gaumata in the fortress of
Sikayauvati. Darius was proclaimed emperor.
Greek historians -
According to the accounts of Greek historians, Cambyses II had left Patizeithes in charge of the kingdom when he headed for Egypt. He later
sent Prexaspes to murder Bardiya. After the killing, Patizeithes put his brother Gaumata, a Magian who resembled Bardiya, on the throne and
declared him the emperor. Otanes discovered that Gaumata was an impostor, and along with six other Iranian nobles including Darius, created a
plan to oust the pseudo-Bardiya. After killing the impostor along with his brother Patizeithes and other Magians, Darius was crowned emperor
the following morning....