Philip III Arrhidaios was a king of Macedonia who ruled from 323 to 317 BC. He was the son of King Philip II and his fourth wife, Philinna of Larissa.

He was born with a physical and mental disability, which made him unfit to rule. He was also a half-brother of Alexander the Great, who succeeded Philip II in 336 BC.

When Alexander died in Babylon in 323 BC, he left no clear heir to his vast empire. A power struggle ensued among his generals and relatives, who formed two factions: the Perdiccan faction, which supported Arrhidaios as king, and the Antipatrid faction, which supported Alexander’s infant son by Roxana, Alexander IV. The two factions agreed to a compromise: Arrhidaios and Alexander IV would be joint kings, with Perdiccas as their regent.

However, this arrangement did not last long. Perdiccas was assassinated in 321 BC by his own officers, who were unhappy with his ambitions and policies. A new regent, Antipater, was appointed by a council of generals in Triparadisus.

Antipater was the leader of the Antipatrid faction and the father of Cassander, who had a personal rivalry with Arrhidaios. Antipater treated Arrhidaios with contempt and disrespect, and tried to undermine his authority.

In 319 BC, Antipater died and appointed Polyperchon as his successor. Polyperchon was an old general of Alexander who had been loyal to Arrhidaios. He tried to restore Arrhidaios’ dignity and power by issuing an edict that granted freedom and autonomy to the Greek cities, and invited them to join him in a war against Cassander.

Cassander, who had seized Macedonia after Antipater’s death, opposed Polyperchon and allied himself with other generals, such as Ptolemy in Egypt and Antigonus in Asia.

The war between Polyperchon and Cassander lasted for several years, with shifting alliances and fortunes. In 317 BC, Polyperchon was defeated by Cassander at Megalopolis, and fled to Epirus with Arrhidaios and his wife Eurydice II, who was also a granddaughter of Philip II.

Cassander pursued them and besieged them in Pydna. He offered to spare Arrhidaios’ life if he surrendered, but Arrhidaios refused. Cassander then bribed some of Polyperchon’s soldiers to kill Arrhidaios and Eurydice in their tent.

Arrhidaios’ death marked the end of his short and tragic reign as king of Macedonia. He was a pawn in the hands of powerful men who used him for their own interests.

He had no real power or influence over his own destiny. He was buried with honors in Aegae, the ancient capital of Macedonia, where his father Philip II had also been buried.