Darius I of Persia in Wikipedia
Darius I was the third king of kings of the Achaemenid
Empire. Darius held the empire at its peak, then including
Egypt, 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 Gaumata 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' life
was his expedition to punish Athens and Eretria and
subjugate Greece (an attempt which failed). Darius expanded
his empire by conquering Thrace and Macedon, and invading
the Saka, Iranian tribes who had invaded Medes and even
killed Cyrus the Great. 
Darius organized the empire, by dividing it into provinces
and placing governors to govern it. He organized a new
monetary system, along with making Aramaic the official
language of the empire. Darius also worked on construction
projects throughout the empire, focusing on Susa, 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...
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