1. Tetrarch of Galatia. He is said by Plutarch to have been a very old man in B. C. 54, when Crassus, passing through Galatia on his Parthian expedition, rallied him on his building a new city at his time of life. He must therefore have attained to mature manhood in B. C. 95, the year of the birth of Cato of Utica, whose father's friend he was, and who, we know, was left an orphan at a very early age. (Plut. Crass. 17, Cat. Min. 12, 15; Pseudo-Appian, Parth. p. 136; comp, CATO, p. 647a.) Deiotarus adhered firmly to the Romans in their wars in Asia, and in B. C. 74 defeated in Phrygia the generals of Mithridates. For his services he was honoured by the senate with the title of king, and, probably in B. C. 63, the year of the death of Mithridates, had Gadelonitis and Armenia Minor added to his dominions. Appian, apparently by an oversight, says that Pompey made him tetrarch of Galatia. He succeeded, indeed, doubtless by Roman favour, in encroaching on the rights of the other tetrarchs of that district, and obtaining nearly the whole of it for himself. (Strab. xii. pp. 547, 567; Casaub. ad loc.; Plut. Pomp. 38; Appian, Bell. Mithr. 114; Cic. pro Deiot. 13, Phil. 11.12, de Har. Resp. 13; Hirt. Bell. Alex. 67.) In B. C. 51, when Cicero was encamped at Cybistra on the borders of Cappadocia, for the protection of Cappadocia and Cilicia against the Parthians, Deiotarus offered to join him with all his forces, and was indeed on his way to do so, when Cicero sent to inform him that events had rendered his assistance unnecessary. (Cic. Phil. 11.13, ad Fam. 8.10, 15.1, 2, 4.) In the civil war, Deiotarus attached himself to the cause of Pompey, together with whom he effected his escape in a ship after the battle of Pharsalia in B. C. 48. (Plut. Pomp. 73 ; Appian, App. BC 2.71; Caes. Civ. 3.4; Cic. de Div. 2.37, pro Deiot. 3, 4; Lucan. Phars. 5.55, 8.209.) In B. C. 47 he applied to Domitius Calvinus, Caesar's legate in Asia, for aid against Pharnaces, who had taken possession of Armenia Minor, and who in the campaign which followed defeated the Roman and Galatian forces near Nicopolis. (Hirt. Bell. Alex. 34-41, 65-77; Appian, App. BC 2.91; Plut. Cues. 50; D. C. 42.45_48; Sueton. Jul. 35; Cic. Fam. 15.15, pro Deiot. 5.) When Caesar, in the same year, came into Asia from Egypt, Deiotarus received him with submission, and endeavorred to excuse the aid he had given to Pompey. According to Hirtius (Bell. Ales. 67, 78), Caesar left him his title of king, but gave his tetrarchy to Mithridates of Pergamus. Cicero tells us (de Div. 1.15, comp. Phil. 2.37), that he was deprived both of his tetrarchy and kingdom, not however of his regal title (pro Deiot. 13), and tined. Dio Cassius says (41.63), that Caesar did indeed bestow on Ariobarzanes, king of Cappadocia, a portion of the kingdom of Deiotarus, but that he gave the latter a part of what he took away from Pharnaces, and so in fact enlarged his territory; but this seems inconsistent with the whole tenour of what we find in Cicero.
In the autumn of the same year, the cause of Deiotarus was unsuccessfully pleaded by Brutus before Caesar at Nicaea in Bithynia. (Cic. Brut. 5, ad Att. 14.1.) In B. C. 45, he was defended by Cicero before Caesar, in the house of the latter at Rome, in the speech (pro Rege Deiotaro) still extant. From this it appears that his grandson, Castor, had accused him of a design against Caesar's life when he received him in Galatia, and also of an intention of sending troops to the aid of Caecilius Bassus. [See p. 472.] Strabo, however, speaks of Castor as the son-in-law of Deiotarus, and says that the old king put him to death together with his wife, Deiotarus's own daughter; and Suidas tells us that he did so because Castor had accused him to Caesar. Vossius conjectures that the Castor mentioned by Cicero was son to the one whom Strabo and Suidas speak of, and that Deiotarus put the latter to death because he head instigated the younger Castor to accuse him. (Strab. xii. p.568; Suid. s. v. Κάστωρ; Caes. Civ. 3.4; Cic. Fam. 9.12; Voss. de Hist. Graec. p. 203, ed. Westermann; comp. the language of Cicero, pro Deiot. 10, 11.) At this time Blesamius and Hieras,