Amyntas III (r.393-369 BC) of Macedon was the father of Philip II, and had a long but unstable reign, dominated by wars with the Illyrians and the Olynthians.
Amyntas came to the throne after a period of some confusion. In 399 King Archelaus I was killed while out hunting. He was succeeded by his young son Orestes, who ruled alongside his guardian Aeropus for four years. After the death of Orestes (possibly killed by Aeropus), his guardian ruled alone as Aeropus II. According to Diodorus, Aeropus died of an illness after a reign of six years, and was succeeded by his son Pausanias. Eusebius, writing several centuries later, gives two king lists, which only serve to complicate things, contradict each other, and in one case misses out Amyntas III altogether (going from Pausanias straight to Ptolemy Alorites, who briefly ruled in the period after Amyntas's death. The second list gives Amyntas two periods in power, of six and eighteen years (the same 24 as Diodorus), but with a two year gap for Argaeus, son of Pausanias.
Diodorus gives two versions of the start of his reign. In both cases he came to the throne after assassinating Pausanias, but was soon driven out by an Illyrian invasion. In despair he gave some of his territory to Olynthus, on his eastern borders, perhaps in the hope that they could defend it until he regained the throne. In the first version Amyntas went into exile in Thessaly, and was soon restored by the Thessalians. In the second the usurper Argaeus ruled for two years, before Amyntas was able to regain the throne.
The confusion isn't helped by the presence of an earlier Amyntas, the ruler of upper Macedonia during the reign of Perdiccas II. In 429 BC this Amyntas, with Thracian support, attempted to seize the throne of Macedon. Perdiccas was able to negotiate a peace agreement, and Amyntas remained limited to Upper Macedon. Some early sources merge the two men, making our man Amyntas II, but they are generally now split into two, with the earlier claimant as Amyntas II and ours as Amyntas III.
After regaining his throne, Amyntas III asked Olynthus to return the border areas he had handed over at the start of his reign. The Olynthians refused, and instead began an invasion of Macedon, posing as the liberators of the Macedonian cities. They may even have taken Pella, the capital and largest city in the kingdom. By now the Olynthians were alarming most of their neighbours, and in 382 BC envoys from Acanthus and Apollonia went to Sparta to ask for help. This was the period of the King's Peace, which had ended the Corinthian War and left Sparta as the main power in Greece, with the authority to defend the autonomy of other Greek cities. The Spartans decided to aid Amyntas, Acanthus and Apollonia. They agreed to send 2,000 men under Eudamidas immediately, while the main army followed on the overland route, under Eudamidas's brother Phoebidas. It was while marching north on the way to Macedon that Phoebidas took a chance to seize control of Thebes. Three years later a group of Theban exiles expelled the Spartans, triggering the Theban-Spartan or Boeotian War. This ended with the disastrous Spartan defeat at Leuctra (371 BC), and the decision to intervene in the north can thus be seen as playing a significant part in the decline of Sparta.
In the short term the decision triggered a short but rather costly war (Olynthian-Spartan War, 383-379 BC). Eudamidas was welcomed into Potidaea, but otherwise didn’t achieve much. The Spartans decided to send a second army, 10,000 men commanded by Teleutias, the half brother of Agesliaus II. He asked Amyntas to hire mercenaries, and to form allies with his neighbouring rulers. Eudamidas had a brief but eventful time in the north. Late in 382 he was almost defeated in battle outside Olynthus, but was saved by King Derdas, one of his Thracian allies. Early in 381 he defeated an Olynthian cavalry raid at Apollonia, but later in 381 he was defeated and killed in a second battle outside Olynthus. The Spartans responded by sending their junior king, Agesipolis I, with thirty advisors, but he soon fell ill and died. Finally they sent Polybiades, who besieged Olynthus and forced the Olynthians to surrender on terms. They had to become Spartan allies, have the same friends and enemies as the Spartans, and dissolve the Chalcidian League. Presumably Amyntas also got his land back.
During the 370s Amyntas attempted to secure his position by forming alliances with Jason of Pherae, then establishing himself as the ruler of Thessaly, and with the Athenians. He secured his alliance with Athens by supporting their claim to Amphipolis, which became something of an obsession for the Athenians, and by adopting the Athenian general Iphicrates as his son. Iphicrates would later help Amyntas's son Perdiccas III secure his claim to the throne.
Towards the end of his life Amyntas's position may have been threatened by Ptolemy of Alorus, said to have been the son-in-law and lover of his wife Eurydice. She planned to assassinate Amyntas, but was foiled by her daughter.
Although Macedon was on the edge of the Greek world., a series of significant figures still ended up working there. Nicomachus, the father of Aristotle, served as the court physician for Amyntas, and Aristotle ended up serving as the tutor for his grandson Alexander the Great.
Amyntas died in 370-369 BC, leaving three certain legitimate sons, each of whom ended up ruling Macedon - Alexander II (369-366 BC), Perdiccas III (365-59) and Philip II, the father of Alexander the Great.