BRENNUS, the name, or perhaps the official title, of two chiefs of the Celtic Gauls.
(1) The first Brennus crossed the Apennines in 391 B.C., ravaged Etruria, and annihilated a Roman army of about 40,000 men on the Allia some 12 m. from Clusium (July 16, 390). Rome thus lay at his mercy, but he wasted time, and the Romans were able to occupy and provision the Capitol (though they had not sufficient forces to defend their walls) and to send their women and children to Veii. When on the third day the Gauls took possession, they found the city occupied only by those aged patricians who had held high office in the state. For a while the Gauls withheld their hands out of awe and reverence, but the ruder passions soon prevailed. The city was sacked and burnt; but the Capitol itself withstood a siege of more than six months, saved from surprise on one occasion only by the wakefulness of the sacred geese and the courage of Marcus Manlius. At last the Gauls consented to accept a ransom of a thousand pounds of gold. As it was being weighed out, the Roman tribune complained of some unfairness. Brennus at once threw his heavy sword into the scale; and when asked the meaning of the act, replied that it meant Vae victis (“woe to the conquered”). The Gauls returned home with their plunder, leaving Rome in a condition from which she took long to recover. A later legend, probably an invention, represents M. Furius Camillus as suddenly appearing with an avenging army at the moment when the gold was being weighed, and defeating Brennus and all his host.
See Livy v. 33-49; Plutarch, Camillus, 17, 22, 28; Polybius i. 6, ii. 18; Dion. Halic. xiii. 7.
(2) The second Brennus is said to have been one of the leaders of an inroad made by the Gauls from the east of the Adriatic into Thrace and Macedonia (280), when they defeated and slew Ptolemy Ceraunus, then king of Macedonia. Whether Brennus took part in this first invasion or not is uncertain; but its success led him to urge his countrymen to a second expedition, when he marched with a large army through Macedonia and Thessaly until he reached Thermopylae. To this point the united forces of the northern Greeks—Athenians, Phocians, Boeotians and Aetolians—had fallen back; and here the Greeks a second time held their foreign invaders in check for many days, and a second time had their rear turned, owing to the treachery of some of the natives, by the same path which had been discovered to the Persians two hundred years before. Brennus and his Gauls marched on to Delphi, of whose sacred treasures they had heard much. But the little force which the Delphians and their neighbours had collected—about 4000 men—favoured by the strength of their position, made a successful defence. They rolled down rocks upon their enemies as they crowded into the defile, and showered missiles on them from above. A thunderstorm, with hail and intense cold, increased their confusion, and on Brennus himself being wounded they took to flight, pursued by the Greeks all the way back to Thermopylae. Brennus killed himself, “unable to endure the pain of his wounds,” says Justin; more probably determined not to return home defeated.
See Justin xxiv. 6; Diod. Sic. xxii. 11; Pausanias x. 19-23; L. Contzen, Die Wanderungen der Kelten (Leipzig, 1861).