This able general. from whom descended a line of Roman emperors, after having acquired a great military reputation, was sent A. D. 367 by Valentinian I. to drive away the Picts and Scots, who were ravaging Britain. Theodosius crossed the straits from Boulogne with his troops of Heruli, Batavians, Jovii, and Victores, and landed at Sandwich. On his road to London he defeated several hordes of the barbarian invaders ; and the citizens of London, who were despairing of their safety, gladly received him within their walls. After establishing order and confidence, he commenced his operations against the invaders, and in two campaigns cleared the province of its savage enemies, and repaired and strengthened the military positions. He drove the Caledonians to the northern part of the island. and formed a province or provincial division of Valentia, or Valentiniana, so named in honour of Valentinian. This tract composed the country between the wall of Severus and the rampart of Antoninus, which Theodosius recovered from the enemy. The history of these campaigns is recorded by Ammianus Marcellinus (27.8, 28.3). Claudian leads us to infer that Theodosius also pursued the enemies of Rome on the stormy seas of the North; and the Orkneys and Thule were stained with the blood of the Picts and the Saxons. (In Quart. Cons. Honor. 31, &c.)
Theodosius, on his return from Britain A. D. 370, was rewarded for his services with the rank of master-general of the cavalry, and being stationed on the Upper Danube, he defeated the Alemanni. In A. D. 372, Firmus, a Moor, the son of Nabal or Nubal, the most powerful of the Moorish princes who professed obedience to the sovereignty of Rome, revolted against the Roman authority; and the natives, who were exasperated at the tyranny of Count Romanus, the governor of A frica, joined the standard of Firmus. The Moorish chieftain plundered Caesarea, on the site of the modern Algiers, and made himself master of Mauritania and Numidia ; and he is said to have assumed the title of king. Romanus being unable to oppose this active enemy, Theodosius was sent to Africa about the close of 372 or the beginning of 373. He sailed from the Rhone and landed at Igilgilis, before the Moorish chief heard of his coming. The first step of Theodosius was to arrest Romanus, whose maladministration was considered to be the cause of the revolt. The campaign against Firmus is recorded by Ammianus (29.5) in a long, most confused, and corrupt chapter, out of which Gibbon has extracted a narrative. Firmus had the cunning and treachery of Jugurtha, and Theodosius displayed all the talents of Metellus, in his negotiations with the Moor, and in pursuit of him through a country which presented unexpected difficulties to regular troops. Firmus at last fled to Igmazen, king of the Isaflenses, a people of whose position Ammianus gives no indication. Igmazen was summoned to surrender Firmus, and after having felt the Roman power, and the consequences of refusal, he determined to give him up. Firmus escaped by a voluntary death. He first made himself drunk, and while his guards were asleep, hanged himself by a rope, which he fixed to a nail in the wall. The dead body was given up to Theodosius, who led his troops back to Sitifis. In the reign of Valens, A. D. 376, Theodosius was beheaded at Carthage. The cause of his execution is unknown. (Gibbon, Decline and Fall, vol. 4.100.25; Tillemont, Histoire des Empereurs, vol. v., where all the authorities are referred to.)
[G.L]