He was born to Tydeus and Deipyle and later became King of Argos, succeeding his maternal grandfather, Adrastus. In Homer's Iliad, Diomedes is regarded alongside Ajax as one of the best warriors of all the Achaeans (behind only Achilles in prowess). In Virgil's Aeneid he is one of the warriors who entered the Trojan Horse shortly before the sack of Troy.
Diomedes was, on his father’s side, an Aetolian, and on his mother's an Argive. This is so because his father Tydeus left Calydon and fled to Argos in order to avoid being persecuted by his uncle Agrius. He married King Adrastus's daughter Deipyle.
Tydeus participated in the expedition, known as the Seven Against Thebes. This expedition failed and all leaders, including Tydeus were killed. Tydeus was Athena’s favourite warrior at the time, and when he was dying she wanted to offer him a magic elixir (which she had obtained from her father) that would make him immortal. However, she withdrew the intended privilege in apparent disgust when Tydeus gobbled down the brains of the hated enemy who had wounded him.
According to some, Diomedes was 4 years old when his father was killed. At the funeral of their fathers, the sons of Seven Against Thebes (Aegialeus, Alcmaeon, Amphilocus, Diomedes, Euryalus, Promachus, Sthenelus, Thersander) met and vowed to vanquish Thebes one day. They called themselves "Epigoni" because they were born "after everything has happened".
Ten years later, the Epigoni appointed Alcmaeon as their commander in chief and gathered an army. They added to their forces from Argos contingents from Messenia, Arcadia, Corinth, and Megara. This army, however, was a small one compared to the forces of Thebes.
The Epigoni war is remembered as the most important expedition in Greek Mythology before the Trojan War. It was a favorite topic for epics, but, unfortunately, all of these epics are now lost. The main battle took place at Glisas where the warrior Aegialeus (son of King Adrastus of Argos) was slain by King Laodamas. Diomedes was 15 years old by then and was considered the mightiest of all. Vanquished by the Epigoni, the Thebans followed the counsel of Tiresias and fled away. Epigoni took the city and most Argive commanders returned rich to their countries after having sacked Thebes, but the city they handed over to Thersander.
Adrastus died of grief when he learned that his son Aegialeus had perished in the battle at Glisas. Aegialeus was married to Comaetho, daughter of Tydeus (sister of Diomedes). Diomedes, in turn, married Aegialeus's daughter Aegialia when he returned from battle. He was then appointed as the King of Argos and thus became one of the most powerful rulers of Hellas at such a young age.
According to some, Diomedes ruled Argos for more than five years and brought much wealth and stability to the city during his time. He was a skilled politician and was greatly respected by other rulers. He still kept an eye on Calydonian politics (his father's homeland), and when the sons of Agrius (led by Thersites) put Oeneus (Diomedes’ grandfather) in jail and their own father on the throne, Diomedes decided to restore the throne to Oeneus.
Diomedes attacked and ceded the Kingdom, slaying all the traitors except Thersites, Onchestus (who escaped to Peloponnesus) and Agrius (who killed himself) restoring his grandfather to the throne. Later, Oeneus passed the Kingdom to his son-in-law Andraemon and headed for Argos to meet Diomedes. He was assassinated on the way (in Arcadia) by Thersites and Onchestus. Unable to find the murderers, Diomedes founded a mythical city called "Oenoe" at the place where his grandfather was buried to honour his death. Later, Thersites fought against the Trojans in the Trojan War and noble Diomedes did not mistreat him (however, Thersites was hated by all Achaeans). In fact, when Thersites was brutally slain by Achilles (after having mocked him when the latter cried over Penthesilia's dead body) Diomedes was the only person who wanted to punish Achilles.
After some years, Diomedes became one of the Suitors of Helen and, as such, he was bound by The Oath of Tyndareus, which established that all the suitors would defend and protect the man who was chosen as Helen's husband against any wrong done against him in regard to his marriage. Accordingly, when the seducer Paris stole Menelaus' wife, all those who had sworn the oath were summoned by Agamemnon (Menelaus’ brother), so that they would join the coalition that was to sail from Aulis to Troy in order to demand the restoration of Helen and the Spartan property that was stolen.
- ^ Dict. Cret. ii. 15 ; comp. Paus. x. 31. § 1.
- ^ Tzetz. ad Lycoph. 993 ; Dict. Cret. iv. 3.
- ^ Dict. Cret. v. 4
- ^ Virg. Aen. ii. 163
- ^ Eustath. ad Hom. p. 822.
- ^ Plut. Quaest. Graec. 48.
- ^ Paus. ii. 28. § 9.
- ^ Serv. ad Aen. ii. 166, iii. 407, iv, 427, v. 81.
- ^ Dictys Cretensis 6. 2; Tzetzes on Lycophron 609; Servius on Aeneid 8. 9.
- ^ Tzetzes on Lycophron 602
- ^ Plut. Parall. Gr. et Rom. 23.
- ^ Serv. ad Aen viii. 9, xi. 246; Strab. vi. pp. 283, 284; Plin. H. N. iii. 20; Justin, xii. 2.
- ^ Paus. i. 11; Serv. ad Aen. viii. 9.
- ^ Plut. de Flum. 18; Paus. ii. 24. § 2
- ^ Schol. ad Pind. Nem. x. 12 ; Scylax, Peripl. p. 6; comp. Strab. v. p. 214, &c.