Xerxes I (ruled 486-465 BCE), also known as Xerxes the Great, was a king of the Persian Achaemenid Empire. His official title was Shahanshah which, though usually translated as `emperor’, actually means `king of kings’. He is identified as the Ahasuerus of Persia in the biblical Book of Esther (although his son, Artaxerxes I, is also a possibility as is Artaxerxes II) and is referenced at length in the works of Herodotus, Diodorus Siculus, Quintus Curtius Rufus, and, to a lesser extent, in Plutarch. Herodotus is the primary source for the story of his expedition to Greece. The name `Xerxes’ is the Greek version of the Persian `Khshayarsa’ (or Khashyar Shah), and so he is known in the west as `Xerxes’ but in the east as `Khshayarsa'.
His mother was Atossa, the daughter of Cyrus the Great (who founded the Achaemenid Empire). He was, therefore, accepted as a great king before having to prove himself so in any way. Xerxes is celebrated for his many building projects throughout his empire but is best known, in both ancient and modern sources, for the massive expedition he mounted against Greece in 480 BCE which, according to Herodotus, assembled the largest and most well equipped fighting force ever put into the field up to that point. He was the son of Darius the Great (550-486 BCE) who, in an effort to punish Athens for their support of the Ionian colonies' revolt against Persian rule, had invaded Greece in 492 BCE. The Persians were defeated by the Greek forces at the Battle of Marathon in 490 BCE, and Darius died in 486 BCE before he could mount another offensive. It therefore fell to his son to carry out his father’s wishes and, in amassing an army of such size and strength, Xerxes felt confident of his success in achieving what the great Darius had been unable to realize.