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).

He was in Babylon at the time of Alexander's death on 10 June 323 BC.
A succession crisis ensued.
 Arrhidaeus was the most obvious candidate, but he was mentally disabled and thus unfit to rule.
A conflict then arose between Perdiccas, leader of the cavalry, and Meleager, who commanded the phalanx: the first wanted to wait to see if Roxana, Alexander's pregnant wife, would deliver a male baby, while the second objected that Arrhidaeus was the closest living relative and so should be chosen king.
Meleager was killed, and a compromise was engineered: Arrhidaeus would become king, with the name of Philip, and he would be joined by Roxana's yet-unborn child as co-sovereign should that child prove a male.
This eventuality did indeed arise and resulted in Roxana's son, Alexander, becoming with his uncle Phillip III co-sovereign on the throne of Macedon.
It was immediately decided that Philip Arrhidaeus would reign, but not rule: this was to be the prerogative of the new regent, Perdiccas.

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.
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.
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.
From that moment on, Philip Arrhidaeus was to be under the sway of his bride, a proud and determined woman bent on substantiating her husband's power.

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.
An agreement was made at Triparadisus in Syria in 321 BC.
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.

The regent died of natural causes the following year, nominating as his successor not his son Cassander, but his friend and lieutenant, Polyperchon.
Cassander's refusal to accept his father's decision sparked the Second War of the Diadochi, in which Eurydice saw once again a chance to free Philip from the control of the regent.

An opportunity presented itself in 317 BC when Cassander expelled Polyperchon from Macedonia.
Eurydice immediately allied herself with Cassander and persuaded her husband to nominate him as the new regent.
Cassander reciprocated by leaving her in full control of the country when he left to campaign in Greece.

But individual circumstances and events at this time were subject to rapid change.
 That same year, Polyperchon and Olympias allied with her cousin, Aeacides, king of Epirus, and invaded Macedonia.
The Macedonian troops refused to fight Olympias, the mother of Alexander.
Philip and Eurydice had no choice but to escape, only to be captured at Amphipolis and thrown into prison.
It soon became clear that Philip was too dangero
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).
He was in Babylon at the time of Alexander's death on 10 June 323 BC. A succession crisis ensued.  Arrhidaeus was the most obvious candidate, but he was mentally disabled and thus unfit to rule. A conflict then arose between Perdiccas, leader of the cavalry, and Meleager, who commanded the phalanx: the first wanted to wait to see if Roxana, Alexander's pregnant wife, would deliver a male baby, while the second objected that Arrhidaeus was the closest living relative and so should be chosen king. Meleager was killed, and a compromise was engineered: Arrhidaeus would become king, with the name of Philip, and he would be joined by Roxana's yet-unborn child as co-sovereign should that child prove a male. This eventuality did indeed arise and resulted in Roxana's son, Alexander, becoming with his uncle Phillip III co-sovereign on the throne of Macedon. It was immediately decided that Philip Arrhidaeus would reign, but not rule: this was to be the prerogative of the new regent, Perdiccas.
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. 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. 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. From that moment on, Philip Arrhidaeus was to be under the sway of his bride, a proud and determined woman bent on substantiating her husband's power.
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. An agreement was made at Triparadisus in Syria in 321 BC. 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.
The regent died of natural causes the following year, nominating as his successor not his son Cassander, but his friend and lieutenant, Polyperchon. Cassander's refusal to accept his father's decision sparked the Second War of the Diadochi, in which Eurydice saw once again a chance to free Philip from the control of the regent.
An opportunity presented itself in 317 BC when Cassander expelled Polyperchon from Macedonia. Eurydice immediately allied herself with Cassander and persuaded her husband to nominate him as the new regent. Cassander reciprocated by leaving her in full control of the country when he left to campaign in Greece.
But individual circumstances and events at this time were subject to rapid change.  That same year, Polyperchon and Olympias allied with her cousin, Aeacides, king of Epirus, and invaded Macedonia. The Macedonian troops refused to fight Olympias, the mother of Alexander. Philip and Eurydice had no choice but to escape, only to be captured at Amphipolis and thrown into prison. It soon became clear that Philip was too dangero
Philip III of Macedon