), an Athenian commander during the Peloponnesian war, came out early in the campaign of B. C. 412, the first after the Syracusan disaster, with a supply of 16 ships for the defence of Ionia. Chios and Miletus were already in revolt, and the Chians presently proceeded to attempt its extension to Lesbos. Diomedon, who had captured on his first arrival four Chian ships, was soon after joined by Leon with ten from Athens, and the two commnanders with a squadron of 25 ships now sailed for Lesbos. They recovered Mytilene at once, defeating the Chian detachment in the harbour; and by this blow were enabled to drive out the enemy and secure the whole island, a service of the highest importance. They also regained Clazomenae, and from Lesbos and the neighboring coast carried on a successful warfare against Chios. (Thuc. 8.19
In this service it seems likely they were permanently engaged until the occasion, in the following winter, when we find them, on the recommendation of Peisander, who with his oligarchical friends was then working for the recall of Alcibiades, placed in the chief command of the fleet at Samos, superseding Phrynichus and Scironides.
After acting against Rhodes, now in revolt, they remained, apparently, during the period of inaction at the commencement of the season of B. C. 411, subordinate to Peisander, then at Samos. Hitherto he had trusted them : their appointment had been perhaps the result of their successful operations in Lesbos and Chios, and of a neutrality in party-matters : perhaps they had joined in his plan for the sake of the recall of Alcibiades, and now that this project was given up, they drew back, and saw moreover, as practical men, that the overthrow of democracy would be the signal foruniversal revolt to Sparta : Thucydides says that they were influenced by the honours they received from the democracy. For whatever reason, they now, on Peisander's departure, entered into communication with Thrasybulus and Thrasyllus, and, acting under their direction, crushed the oligarchical conspiracy among the Samians, and on hearing that the government of the Four Hundred was established in Athens, raised the standard of independent democracy in the army, and recalled Alcibiades. (8.54, 55, 73.)
Henceforth for some time they are not named, though they pretty certainly were among the commanders of the centre in the battle of Cynossema, and during the whole period of the command of Alcibiades were probably in active service. When after the battle of Notium, B. C. 407, he was disgraced, they were among the ten generals appointed in his room. Diomedon in this command was employed at a distance from the main fleet; and when Callicratidas chased Conon into Mytilene, on the information, perhaps, of the galley which made its escape to the Hellespont, he sailed for Lesbos, and lost 10 out of 12 ships in attempting to join his besieged colleague.
In the subsequent glorious victory of Arginusae, he was among the commanders. So was healso among those unhappy six who returned to Athens and fell victims to the mysterious intrigues of the oligarchical party and the wild credulity of the people.
It was in his behalf and that of Pericles, that his friend Euryptolemus made the attempt, so nearly successful, to put off the trial.
According to the account given in his speech, Diomedon, after the engagement, when the commanders met, had given the advice to form in single file and pick up the castaways ; and after Theramenes and Thrasybulus had been prevented by the storm from effecting their commission to the same purpose, he with Pericles had dissuaded his colleagues from naming those officers and this commission in their despatch, for fear of their incurring the displeasure which thus in the end fell on the generals themselves. (Xenoph. Hell. 1.5.16
. §§ 22, 29, 7. §§ 1, 16, 17, 29.) Diodorus, who hitherto had not mentioned his name, here relates that Diomedon, a man of great military skill, and distinguished for justice and other virtues, when sentence had been passed and he and the rest were now to be led to execution, came forward and bade the people be mindful to perform, as he and his colleagues could not, the vows which before the engagement they had made to the gods. (Diod. 13.102