Arcesilaus was the son of the fifth Cyrenaean King, Battus III and queen Pheretima.
In 525 BC, Arcesilaus made an alliance with King Cambyses II of Persia.
About 518 BC, Arcesilaus could no longer accept the Cyrenaean constitutional changes introduced by his late father and the Greek lawmaker, Demonax, and demanded the restoration of his ancestral rights.
In Samos, Arcesilaus recruited men for his army by promising to grant them land in Cyrene.
His supporters received their land, but out of fear of a backlash (and ignoring the oracle's advice), Arcesilaus left Cyrene and went to the Cyrenaean town of Barca, whose governor, Alazir, was his father-in-law.