In the early part of the reign of Honorius, the vigilance of Stilicho had successfully guarded the remote island of Britain from her incessant enemies of the ocean, the mountains, and the Irish coast. But those restless Barbarians could not neglect the fair opportunity of the Gothic war, when the walls and stations of the province were stripped of the Roman troops. If any of the legionaries were permitted to return from the Italian expedition, their faithful report of the court and character of Honorius must have tended to dissolve the bonds of allegiance, and to exasperate the seditious temper of the British army. The spirit of revolt, which had formerly disturbed the age of Gallienus, was revived by the capricious violence of the soldiers; and the unfortunate, perhaps the ambitious, candidates, who were the objects of their choice, were the instruments, and at length the victims, of their passion. Marcus was the first whom they placed on the throne, as the lawful emperor of Britain and of the West. They violated, by the hasty murder of Marcus, the oath of fidelity which they had imposed on themselves; and _their_ disapprobation of his manners may seem to inscribe an honorable epitaph on his tomb. Gratian was the next whom they adorned with the diadem and the purple; and, at the end of four months, Gratian experienced the fate of his predecessor. The memory of the great Constantine, whom the British legions had given to the church and to the empire, suggested the singular motive of their third choice. They discovered in the ranks a private soldier of the name of Constantine, and their impetuous levity had already seated him on the throne, before they perceived his incapacity to sustain the weight of that glorious appellation. Yet the authority of Constantine was less precarious, and his government was more successful, than the transient reigns of Marcus and of Gratian. The danger of leaving his inactive troops in those camps, which had been twice polluted with blood and sedition, urged him to attempt the reduction of the Western provinces. He landed at Boulogne with an inconsiderable force; and after he had reposed himself some days, he summoned the cities of Gaul, which had escaped the yoke of the Barbarians, to acknowledge their lawful sovereign. They obeyed the summons without reluctance. The neglect of the court of Ravenna had absolved a deserted people from the duty of allegiance; their actual distress encouraged them to accept any circumstances of change, without apprehension, and, perhaps, with some degree of hope; and they might flatter themselves, that the troops, the authority, and even the name of a Roman emperor, who fixed his residence in Gaul, would protect the unhappy country from the rage of the Barbarians. The first successes of Constantine against the detached parties of the Germans, were magnified by the voice of adulation into splendid and decisive victories; which the reunion and insolence of the enemy soon reduced to their just value. His negotiations procured a short and precarious truce; and if some tribes of the Barbarians were engaged, by the liberality of his gifts and promises, to undertake the defence of the Rhine, these expensive and uncertain treaties, instead of restoring the pristine vigor of the Gallic frontier, served only to disgrace the majesty of the prince, and to exhaust what yet remained of the treasures of the republic. Elated, however, with this imaginary triumph, the vain deliverer of Gaul advanced into the provinces of the South, to encounter a more pressing and personal danger. Sarus the Goth was ordered to lay the head of the rebel at the feet of the emperor Honorius; and the forces of Britain and Italy were unworthily consumed in this domestic quarrel. After the loss of his two bravest generals, Justinian and Nevigastes, the former of whom was slain in the field of battle, the latter in a peaceful but treacherous interview, Constantine fortified himself within the walls of Vienna. The place was ineffectually attacked seven days; and the Imperial army supported, in a precipitate retreat, the ignominy of purchasing a secure passage from the freebooters and outlaws of the Alps. Those mountains now separated the dominions of two rival monarchs; and the fortifications of the double frontier were guarded by the troops of the empire, whose arms would have been more usefully employed to maintain the Roman limits against the Barbarians of Germany and Scythia.