(Δίαιος), a man of Megalopolis, succeeded Menalcidas of Lacedaemon as general of the Achaean league in B. C. 150. Menalcidas, having been assailed by Callicrates with a capital charge, saved himself through the favour of Diaeus, whom he bribed with three talents [CALLICRATES, No. 4, p. 569b.]; and the latter, being much and generally condemned for this, endeavored to divert public attention from his own conduct to a quarrel with Lacedaemon. The Lacedaemonians had appealed to the Roman senate about the possession of some disputed land, and had received for answer that the decision of all causes, except those of life and death, rested with the great council of the Achaeans. This answer Diaeus so far garbled as to omit the exception. The Lacedaemonians accused him of falsehood, and the dispute led to war, wherein the Lacedaemonians found themselves no match for the Achaeans, and resorted accordingly to negotiation. Diaeus, affirming that his hostility was not directed against Sparta, but against her disturbers, procured the banishment of 24 of her principal citizens. These men fled for refuge and protection to Rome, and thither Diaeus went to oppose them, together with Callicrates, who died by the way. The cause of the exiles was supported by Menalcides, who assured the Spartans, on his return, that the Romans had declared in favour of their independence, while an equally positive assurance to the opposite effect was given by Diaeus to the Achaeans,--the truth being that the senate had passed no final decision at all, but had promised to send commissioners to settle the dispute. War was renewed between the parties, B. C. 148, in spite of the prohibition of the Romans, to which, however, Diaeus, who was again general in B. C. 147, paid more obedience, though he endeavoured to bring over the towns round Sparta by negotiation. When the decree of the Romans arrived, which severed Sparta and several other states from the Achaean league, Diaeus took a leading part in keeping up the indignation of the Achaeans, and in urging them to the acts of violence which caused war with Rome. In the autumn of 147 he was succeeded by Critolaüs, but the death of the latter before the expiration of his year of office once more placed Diaeus at the post of danger, according to the law of the Achaeans, which provided in such cases that the predecessor of the deceased should resume his authority. The number of his army he swelled with emancipated slaves, and enforced strictly, though not impartially, the levy of the citizens ; but he acted unwisely in dividing his forces by sending a portion of them to garrison Megara and to check there the advance of the Romans. He himself had taken up his quarters in Corinth, and Metellus, the Roman general, advancing thither, sent forward ambassadors to offer terms, but Diaeus threw them into prison (though he afterwards released them for the bribe of a talent), and caused Sosicrates, the lieutenantgeneral, as well as Philinus of Corinth, to be put to death with torture for having joined in recommending negotiation with the enemy. Being defeated by Mummius before the walls of Corinth, in B. C. 146, he made no further attempt to defend the city, but fled to Megalopolis, where he slew his wife to prevent her falling into the enemy's power, and put an end to his own existence by poison, thus (says Pausanias) rivalling Menalcidas in the cowardice of his death, as he had rivalled him through his life in avarice. [MENALCIDAS.] (Plb. 38.2, 40.2, 4, 5, 9; Paus. 7.12, &c.; Clinton, F. H. sub annis 149, 147, 146.)