Iranian tribes settled between Zagros and Hindu Kush around 500 BCE. Zoroaster's teachings emphasized universal principles and truth. Medes established empire under Astyages, later conquered Persia. Cyrus II unified Persian tribes and conquered Medes in 550 BCE
Human habitation in Persia dates back 100,000 years to Paleolithic Age. Susa, founded in 4395 BCE, is among world's oldest cities. Aryan tribes migrated to region before 3rd millennium BCE. Zoroaster established Zoroastrianism between 1500-1000 BCE
Xerxes I ruled Persia from 486 to 465 BCE as Shahanshah. He was the first-born son of Darius the Great, married to Cyrus' daughter Atossa. His mother's Persian name was Khshayarsa in the east, Xerxes in the west
Darius became emperor by assassinating Gaumata in 522 BCE. He organized empire into 20 provinces with governors. Created Aramaic as official language and introduced new monetary system
Born in 550 BCE to Hystaspes and Rhodogune, Darius claimed Achaemenid lineage. Became king at age 28 after Cambyses' death, defeating rival Gaumata. His rule was documented in Behistun Inscription in three languages
Darius named Xerxes as his successor despite being his half-brother's birth. Xerxes was 35 years old when he became king. He suppressed Egyptian and Babylonian revolts after his father's death