13 events the sources record for this year, grouped by region.
What happened
West Asia (11)
The Magian priest Gaumata rebels from Mount Arakadri in Paishiyauvada, deceiving people by claiming "I am Smerdis, son of Cyrus" (Behistun Inscription §11 (Col. I 35-39))
Gaumata seizes Persia, Media and all other provinces and takes the throne; then Cambyses dies by his own hand (Behistun Inscription §11 (Col. I 40-44))
With a small force, Darius kills Gaumata and his chief followers at the fortress of Sikayauvatish in the Nisaya district of Media, and becomes king (Behistun Inscription §13 (Col. I 50-61))
Atrina (son of Upadarma) rebels in Susiana, saying "I am king of Susiana," and the Susianians join him (Behistun Inscription §16 (Col. I 73-77))
Nidintu-Bel rebels in Babylon, saying "I am Nebuchadnezzar, son of Nabonidus"; all Babylonia joins him and he seizes the kingship (Behistun Inscription §16 (Col. I 77-81))
Darius sends an army to Susiana; Atrina is brought in chains and executed (Behistun Inscription §17 (Col. I 81-83))
Darius marches on Babylon; Nidintu-Bel's army holds the Tigris and has ships, but Darius crosses the river and defeats it (Behistun Inscription §18 (Col. I 83-89))
Nidintu-Bel fights a second decisive battle at the city of Zazana on the Euphrates; the enemy plunges into the water and is swept away (Behistun Inscription §19 (Col. I 89-96))
Nidintu-Bel flees to Babylon with a few horsemen, but Darius takes Babylon and executes him there (Behistun Inscription §20 (Col. II 1-5))
Phraortes of Media rebels, saying "I am Khshathrita of the family of Cyaxares"; the Medes at court join him and he becomes king (Behistun Inscription §24 (Col. II 13-17))