When Constantine, ... born of an emperor, a pious son of a most pious and prudent father, and Licinius, second to him, — two God-beloved emperors, honored alike for their intelligence and their piety—being stirred up against the two most impious tyrants by God, the absolute Ruler and Savior of all, engaged in formal war against them, with God as their ally, Maxentius was defeated at Rome by Constantine in a remarkable manner, and the tyrant of the East did not long survive him, but met a most shameful death at the hand of Licinius, who had not yet become insane.
Constantine, who was the superior both in dignity and imperial rank, first took compassion upon those who were oppressed at Rome, and having invoked in prayer the God of heaven, and his Word, and Jesus Christ himself, the Savior of all, as his aid, advanced with his whole army, proposing to restore to the Romans their ancestral liberty.
But Maxentius, putting confidence rather in the arts of sorcery than in the devotion of his subjects, did not dare to go forth beyond the gates of the city, but fortified every place and district and town which was enslaved by him, in the neighborhood of Rome and in all Italy, with an immense multitude of troops and with innumerable bands of soldiers. But the emperor, relying upon the assistance of God, attacked the first, second, and third army of the tyrant, and conquered them all; and having advanced through the greater part of Italy, was already very near Rome.
Then, that he might not be compelled to wage war with the Romans for the sake of the tyrant, God himself drew the latter, as if bound in chains, some distance without the gates, and confirmed those threats against the impious which had been anciently inscribed in sacred books—disbelieved, indeed, by most as a myth, but believed by the faithful,— confirmed them, in a word, by the deed itself to all, both believers and unbelievers, that saw the wonder with their eyes.
Thus, as in the time of Moses himself and of the ancient God-beloved race of Hebrews, he cast Pharaoh's chariots and host into the sea, and overwhelmed his chosen charioteers in the Red Sea, and covered them with the flood, in the same way Maxentius also with his soldiers and body-guards went down into the depths like a stone, when he fled before the power of God which was with Constantine, and passed through the river which lay in his way, over which he had formed a bridge with boats, and thus prepared the means of his own destruction.
In regard to him one might say, he dug a pit and opened it and fell into the hole which he had made; his labor shall turn upon his own head, and his unrighteousness shall fall upon his own crown.
Thus, then, the bridge over the river being broken, the passageway settled down, and immediately the boats with the men disappeared in the depths, and that most impious one himself first of all, then the shield-bearers who were with him, as the divine oracles foretold, sank like lead in the mighty waters; so that those who obtained the victory from God, if not in words, at least in deeds, like Moses, the great servant of God, and those who were with him, fittingly sang as they had sung against the impious tyrant of old, saying, "Let us sing unto the Lord, for he has gloriously glorified himself; horse and rider has he thrown into the sea; a helper and a protector has he become for my salvation; and Who is like you, O Lord; among the gods, who is like you glorious in holiness, marvelous in glory, doing wonders." [Exodus 15]
These and the like praises Constantine, by his very deeds, sang to God, the universal Ruler, and Author of his victory, as he entered Rome in triumph.
Immediately all the members of the Senate and the other most celebrated men, with the whole Roman people, together with children and women, received him as their deliverer, their savior, and their benefactor, with shining eyes and with their whole souls, with shouts of gladness and unbounded joy.
But he, as one possessed of inborn piety toward God, did not exult in the shouts, nor was he elated by the praises; but perceiving that his aid was from God, he immediately commanded that a trophy of the Savior's passion be put in the hand of his own statue.
And when he had placed it, with the saving sign of the cross in its right hand, in the most public place in Rome, he commanded that the following inscription should be engraved upon it in the Roman tongue: "By this salutary sign, the true proof of bravery, I have saved and freed your city from the yoke of the tyrant and moreover, having set at liberty both the senate and the people of Rome, I have restored them to their ancient distinction and splendor."
Eusebius
Ecclesiastical History (Book IX)
