This motive of enmity must have inflamed the subjects of contention which perpetually arise on the confines of warlike and independent nations. The Vandal princes were stimulated by fear and revenge; the Gothic kings aspired to extend their dominion from the Euxine to the frontiers of Germany; and the waters of the Marus, a small river which falls into the Theiss, were stained with the blood of the contending barbarians. After some experience of the superior strength and number of their adversaries, the Sarmatians implored the protection of the Roman monarch, who beheld with pleasure the discord of the nations but who was justly alarmed by the progress of the Gothic arms. As soon as Constantine had declared himself in favour of the weaker party, the haughty Araric, king of the Goths, instead of expecting the attack of the legions, boldly passed the Danube, and spread terror and devastation through the province of Mœsia. To oppose the inroad of this destroying host, the aged emperor took the field in person; but on this occasion either his conduct or his fortune betrayed the glory which he had acquired in so many foreign and domestic wars. He had the mortification of seeing his troops fly before an inconsiderable detachment of the barbarians, who pursued them to the edge of their fortified camp and obliged him to consult his safety by a precipitate and ignominious retreat. The event of a second and more successful action retrieved the honour of the Roman name; and the powers of art and discipline prevailed, after an obstinate contest, over the efforts of irregular valour. The broken army of the Goths abandoned the field of battle, the wasted province, and the passage of the Danube; and although the eldest of the sons of Constantine was permitted to supply the place of his father, the merit of the victory, which diffused universal joy, was ascribed to the auspicious counsels of the emperor himself.
He contributed at least to improve this advantage by his negotiations with the free and warlike people of Chersonesus, whose capital, situated on the western coast of the Tauric or Crimæan peninsula, still retained some vestiges of a Grecian colony, and was governed by a perpetual magistrate, assisted by a council of senators, emphatically styled the fathers of the city. The Chersonites were animated against the Goths by the memory of the wars which, in the preceding century, they had maintained with unequal forces against the invaders of their country. They were connected with the Romans by the mutual benefits of commerce, as they were supplied from the provinces of Asia with corn and manufactures, which they purchased with their own productions, salt, wax, and hides. Obedient to the requisition of Constantine, they prepared, under the conduct of their magistrate Diogenes, a considerable army, of which the principal strength consisted in crossbows and military chariots. The speedy march and intrepid attack of the Chersonites, by diverting the attention of the Goths, assisted the operations of the imperial generals.
The Goths, vanquished on every side, were driven into the mountains, where in the course of a severe campaign about a hundred thousand were computed to have perished by cold and hunger. Peace was at length granted to their humble supplications; the eldest son of Araric was accepted as the most valuable hostage; and Constantine endeavoured to convince their chiefs, by a liberal distribution of honours and rewards, how far the friendship of the Romans was preferable to their enmity. In the expressions of his gratitude towards the faithful Chersonites, the emperor was still more magnificent. The pride of the nation was gratified by the splendid and almost royal decorations bestowed on their magistrate and his successors. A perpetual exemption from all duties was stipulated for their vessels which traded to the ports of the Black Sea. A regular subsidy was promised of iron, corn, oil, and every supply which could be useful either in peace or war. But it was thought that the Sarmatians were sufficiently rewarded by their deliverance from impending ruin; and the emperor, perhaps with too strict an economy, deducted some part of the expenses of the war from the customary gratifications which were allowed to that turbulent nation.