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Xerxes I was the grandson of Cyrus the Great, the founder of the Achaemenid Empire. Xerxes' father, Darius I, was Cyrus' son and successor. Xerxes ascended to the throne in 486 BC after Darius' death. He is best known for his failed invasion of Greece in 480 BC, which culminated in the Battle of Thermopylae and the Battle of Salamis.