Sources & Historiography
The evidence for the Achaemenid empire, and how far each kind of it can be trusted. Every source entry carries an explicit evaluation of its reliability and bias.
Herodotus, The Histories
The earliest surviving Greek history, and the fullest classical account of the Persians — their rise, their customs and religion, and the wars with Greece; indispensable, endlessly informative, and to be read with a critical eye as an outsider's report.
Herodotus is an outsider, writing in Greek, a generation or two after the events of Darius's reign and drawing on oral report; he interprets Persian gods through Greek names (calling the high god 'Zeus', confusing Mithra with a goddess of love at 1.131) and shapes his material to Greek narrative and moral patterns. Yet where his statements can be checked against the Persian evidence — the inscriptions, the Persepolis tablets, Babylonian records — he is frequently confirmed in substance, and his ethnography of Persian religion agrees strikingly with the picture from Iranian sources (open-air worship, the Magi, the horror of the Lie). He is neither a naïve fabulist nor a documentary witness: he is the single richest classical informant, to be used critically and cross-checked wherever possible.
The Behistun Inscription (DB)
Darius I's monumental cliff-relief and trilingual inscription recounting his seizure and defence of the throne against Gaumāta and a wave of rebels; the single most important primary source for the reign, and the key that deciphered cuneiform.
Behistun is at once indispensable and treacherous. Indispensable: it is the only long, contemporary, first-person Achaemenid narrative of political events, composed within two years of them and publicly displayed. Treacherous: it is pure royal apologia, written by the victor to justify a violent and contested accession. Its central claim — that the man Darius killed was an impostor magus and not the true Bardiya son of Cyrus — cannot be independently confirmed, and a strand of modern scholarship suspects the reverse: that Darius was the usurper and the 'Lie' framing his masterstroke. The battle-count and casualty figures are the king's own. It should be read as the most authoritative statement of how Darius wished the events to be understood, not as neutral chronicle. Copies in Aramaic (found at Elephantine) and Babylonian show the text was circulated across the empire as official history.