COMMIUS (fl. B.C. 57–51), ambassador from Julius Cæsar to the Britons, and probably a chieftain of southern Britain, was apparently a native of Belgic Gaul. He first comes into notice after the battle of the Sambre (B.C. 57), when Julius Caesar conferred upon him the sovereignty of the Atrebates, a Belgic tribe defeated in that engagement, and one to which Commius himself probably belonged. Caesar recognised in him a man of valour and judgment, and granted him various privileges. Commius was known to possess great influence over the inhabitants of southern Britain, and in B.C. 55 was accordingly chosen by Cæsar (who was then in Belgium among the Morini) as his ambassador to the Britons, and was directed to announce the intended visit of Caesar and to urge the Britons to remain faithful to the Romans. Commius went back with the British legates who had been sent to Caesar, and took with him a small force of about thirty horsemen. On attempting to deliver his message he was seized and thrown into chains; but when Caesar landed in Britain in the same year he was given up to him by the natives. Commius was still in Britain in B.C. 54, and it was through him that Cassivellaunus tendered his submission to Caesar. In B.C. 53, when the great revolt of Gallic chieftains against the Romans began already to threaten, Caesar gave Commius the command of a troop of horsemen stationed to keep watch over the Menapii. In the following year (B.C. 52) the Gaulish revolt took place, and Commius deserted to the side of his fellow-countrymen. He commanded, besides his own Atrebates, a contingent of the Bellovaci consisting of two thousand men, and was one of the chieftains in supreme military authority. With the other headers he marched to the relief of Alesia. In the same year, and probably before these events, he became an object of suspicion to the Romans. Caius Volusenus Quadratus induced him to come to what he pretended was a friendly conference, but the centurion commissioned by Volusenus to kill Commius only struck him a blow with his sword, and the latter escaped with his life. In B.C. 51 the war against Caesar was renewed by the Bellovaci, Atrebates, and other tribes. Commius, who was again one of the chief commanders, went over to the Germani for help, and came back with five hundred horsemen. On the defeat and submission of the Gaulish tribes, he retired for a time to his friends among the Germani. In the winter of the same year (B.C. 51) he returned, and was still anxious to head a revolt; but his own tribe had now submitted, and he had to content himself with the leadership of a band of predatory horsemen who intercepted the supplies intended for the winter quarters of the Romans in Belgium. Marc Antony, who was now in command in that part of the country, sent Caius Volusenus Quadratus, his prefect of horse, in pursuit of Commius. Some fighting took place, and on one occasion Volusenus, who was eager to attack his old enemy in person, received a wound in the thigh from the lance of Commius. The latter mounted on a swift horse evaded the pursuit of the Romans. In the same year (B.C. 51) Commius tendered his submission to Antony, declaring (it is said) that he would do anything that was required of him, provided only that he should never again be brought into the presence of a Roman. These words, according to the colouring given them by Hirtius (viii. 48), were expressive of abject terror on the part of Commius; more probably they were an expression of contempt and disgust (cf. viii. 23). Front inus relates a curious incident, difficult to date and perhaps not worthy of credit, namely that Commius once fled from Gaul to Britain, and induced Caesar, who was following him at a distance, to desist from the pursuit by the stratagem of hoisting his sails before he was actually out at sea. According to De Saulcy (Annuaire) and Hucher (Rev. Num.), certain Gaulish silver coins (obverse, helmeted head; reverse, free horse) inscribed with the words COMMIOS or COMIOS were issued by Commius when chieftain of the Atrebates (see the engraving in Hucher, l'art gaulois, pi. 62, 2; Rev. Num. 1863, pi. xvi. 9; and specimens in Brit. Mus.) Numismatic evidence renders it probable that after his submission to Antony Commius retired to Britain and there acquired the sovereign power over several tribes. Three British chieftains, Tinc[ommius] (ruler in Hampshire and Sussex), Verica (king in Sussex and Surrey), and Eppillus (ruler in Kent), severally issued gold coins inscribed with their individual names accompanied by the title ' son of Commius ' (on this interpretation now quite certain of c. f., commi f., &c.. see Willett in Num. Chron. vol. xvii., N.S. (1877), p. 315), in all probability this Commius. Evans conjectures that he acquired dominion over the tribes of Hampshire, Sussex, Kent, and Surrey, and that after his death his kingdom was broken up and divided among his three sons. To Commius himself there are no coins which can be attributed with certainty, though gold pieces of the type engraved by Evans, pi. i. 10, p. 157 (cf. Willett, Anc. Brit. Coins of Sussex, pp. 51, 52), may possibly be his.
[Cæsar, De Bello Gallico, ii. 23, iv. 21, 27, 35, v. 22, vi. 6, vii. 75, 76, 79, viii. (Hirtius), 6, 7, 10, 21, 23, 47, 48; Frontinus's Stratagem, ii., xiii. 11; Biog. nat. de Belgique, s.v. 'Commius;' Merivale's Hist. of the Romans, i. 406, 409, ii. 71, 72, 73; Evans's Coins of the Ancient Britons, pp. 152-8, 159 ff., 193; Willett's Ancient British Coins of Sussex (reprinted from Sussex Archæeol. Coll. vols. xxix. and xxx.), p. 42 ff.; Willett in Numismatic Chronicle, vol. xvii. New Ser. (1871), p. 315; Hucher's L'art gaulois, pl. 62, 2, and his paper in the Revue Numismatique, 1863, p. 373, pl. xvi. 9; De Saulcy in Annuaire de la Société française de Numismatique, 1867, p. 20; coins in British Museum.]