Plutarch was of the view that he became disabled by means of an attempt on his life by Philip II's wife, Queen Olympias, who wanted to eliminate a possible rival to her son, Alexander, through the employment of pharmaka (drugs/spells); however, most modern authorities doubt the truth of this claim., both to protect his life and to prevent his use as a pawn in any prospective challenge for the throne.
After Alexander's death in Babylon in 323 BC, the Macedonian army in Asia proclaimed Arrhidaeus as king; however, he served merely as a figurehead and as the pawn of a series of powerful generals.
Even though Arrhidaeus and Alexander were about the same age, Arrhidaeus appears never to have been a danger as an alternative choice for Alexander's succession to Philip II; nevertheless, when the Persian satrap of Caria, Pixodarus, proposed his daughter in marriage to Philip, the king declined, offering his son Arrhidaeus as husband instead, and Alexander thought it prudent to block the dynastic union (which might have produced a possible future heir to Philip's domain before Alexander himself did), resulting in considerable irritation on the part of his father (337 BC).
Arrhidaeus' whereabouts during the reign of his brother Alexander are unclear from the extant sources; what is certain is that no civil or military command was given to him in those thirteen years (336–323 BC).
Formerly located at the Thessaloniki Archaeological Museum, since 1997) displayed in the underground museum of Vergina, inside the Great Tumulus.It was immediately decided that Philip Arrhidaeus would reign, but not rule: this was to be the prerogative of the new regent, Perdiccas. Head of Herakles right, wearing lion skin headdress / [BASILEWS FILIPPOU], Zeus Aëtophoros seated left; wheel and monogram in left field, monogram below throne.When news arrived in Macedonia that Arrhidaeus had been chosen as king, Cynane, a daughter of Philip II, developed a plan to travel to Asia and offer the new king her daughter Eurydice for wife. Eurydice's chance to increase her husband's power came when the first war of the Diadochi sealed the fate of Perdiccas, making a new settlement necessary.This move was an obvious affront to the regent, whom Cynane had completely bypassed, and to prevent the marriage, Perdiccas sent his brother, Alcetas, to kill Cynane. An agreement was made at Triparadisus in Syria in 320 BC.The reaction among the troops generated by this murder was such that the regent had to give up his opposition to the proposed match and accept the marriage. Eurydice moved deftly enough to achieve the removal of the first two designated regents, Peithon and Arrhidaeus (a namesake of her husband), but was powerless to block the aspirations of Antipater, whose position proved too powerful, and the latter was made the new regent; Philip Arrhidaeus and Eurydice were forced to follow Antipater back to Macedonia.