Constantine's Conversion to Christianity was a Great Triumph for Christendom and a Great Relief to thousands of Suffering Christians.
The Bible says someone who believes that Jesus is Lord i.e. God will be saved, and thus is a Christian. Ergo, Constantine was Christian.
Constantine certainly believed in the Divinity of Christ. Disagree with him all you like, but you cannot deny this basic fact about him.
From New Advent: "
In deciding for
Christianity he was no doubt also influenced by reasons of
conscience--reasons resulting from the impression made on every unprejudiced
person both by the
Christians and by the
moral force of
Christianity, and from the practical
knowledge which the emperors had of the
Christian military officers and state officials. These reasons are, however, not mentioned in history, which gives the chief prominence to a
miraculous event. Before Constantine advanced against his rival
Maxentius, according to ancient custom he summoned the haruspices, who
prophesied disaster; so reports a
pagan panegyrist. But when the gods would not aid him, continues this writer, one particular god urged him on, for Constantine had close relations with the divinity itself. Under what
form this connection with the deity manifested itself is told by
Lactantius (
How the Persecutors Died 44) and
Eusebius (
Life of Constantine I.26-31). He saw, according to the one in a
dream, according to the other in a vision, a heavenly manifestation, a brilliant light in which he believed he descried the cross or the
monogram of Christ. Strengthened by this
apparition, he advanced
courageously to battle, defeated his rival and won the supreme power. It was the result that gave to this vision its full importance, for when the emperor afterwards reflected on the event it was clear to him that the cross bore the inscription: HOC VINCES (in this sign wilt thou conquer). A monogram combining the first letters, X and P, of the
name of Christ (CHRISTOS), a form that cannot be
proved to have been used by
Christians before, was made one of the tokens of the standard and placed upon the
Labarum. In addition, this ensign was placed in the hand of a
statue of the emperor at
Rome, the pedestal of which bore the inscription: "By the aid of this salutary token of strength I have freed my city from the yoke of tyranny and restored to the Roman Senate and People the ancient splendour and glory." Directly after his victory Constantine granted
tolerance to the
Christians and next year (313) took a further step in their favour. In 313 Licinius and he issued at
Milan the famous joint edict of
tolerance.
This declared that the two emperors had deliberated as to what would be advantageous for the security and welfare of the empire and had, above all, taken into consideration the service which
man owed to the "deity". Therefore they had decided to grant
Christians and all others freedom in the exercise of religion ... Before this, it is
true, it had occurred to Melito of Sardes (
Eusebius,
Church History IV.33) that the emperor might some day become a
Christian, but
Tertullian had thought otherwise, and had written (
Apology 21) the memorable sentence: "Sed et Caesares credidissent super Christo, si aut Caesares non essent saeculo necessarii, aut si et Christiani potuissent esse Caesares" (But the Caesars also would have
believed in Christ, if either the Caesars had not been
necessary to the world or if
Christians too could have been Caesars). The same opinion was held by
St. Justin (I, xii, II, xv). That the empire should become
Christian seemed to
Justin and many others an impossibility, and they were just as little in the wrong as the
optimists were in the right. At all events, a
happy day now dawned for the
Christians. They must have felt as did the
persecuted in the time of the
French Revolution when Robespierre finally fell and the Reign of Terror was over.
The feeling of emancipation from danger is touchingly expressed in the treatise ascribed to
Lactantius (
How the Persecutors Died), concerning the ways in which death overtook the
persecutors. It says: "We should now give thanks to the Lord, Who has gathered together the flock that was devastated by ravening wolves, Who has exterminated the wild beasts which drove it from the pasture. Where is now the swarming multitude of our enemies, where the hangmen of
Diocletian and
Maximian?
God has swept them from the earth; let us therefore celebrate His triumph with
joy; let us observe the victory of the Lord with songs of praise, and
honour Him with
prayer day and night, so that the peace which we have received again after ten years of misery may be preserved to us." The
imprisoned Christians were released from the
prisons and mines, and were received by their brethren in the
Faith with acclamations of
joy; the churches were again filled, and those who had fallen away sought forgiveness."