Continuing the iconography of his predecessors, Constantine's coinage at the time was inscribed with solar symbolism, interpreted as representing Sol Invictus (the Unconquered Sun), Helios, Apollo, or Mithras, but in 325 and thereafter the coinage ceases to be explicitly pagan, and Sol Invictus disappears.
And although Eusebius' Historia Ecclesiae further reports that Constantine had a statue of himself "holding the sign of the Savior [the cross] in his right hand" erected after his victorious entry into Rome, there are no other reports to confirm such a monument.
Having had their shields marked in this fashion, Constantine's troops readied themselves for battle. The first, shorter one in the Ecclesiastical History leaves no doubt that God helped Constantine but does not mention any vision.
In his later Life of Constantine, Eusebius gives a detailed account of a vision and stresses that he had heard the story from the emperor himself.
At the final battle of the war, the Battle of Chrysopolis, Licinius, though prominently displaying the images of Rome's pagan pantheon on his own battle line, forbade his troops from actively attacking the labarum, or even looking at it directly.
Eusebius stated that in addition to the singular labarum of Constantine, other similar standards (labara) were issued to the Roman army.
The name labarum was applied both to the original standard used by Constantine the Great and to the many standards produced in imitation of it in the Late Antique world, and subsequently.
Its first appearance is on a Constantinian silver coin from c.
317, which proves that Constantine did use the sign at that time.
He made extensive use of the Chi-Rho and the labarum later in the conflict with Licinius.
The vision has been interpreted in a solar context (e.g.
During the attack of Constantine's troops at the Battle of Adrianople the guard of the labarum standard were directed to move it to any part of the field where his soldiers seemed to be faltering.
The appearance of this talismanic object appeared to embolden Constantine's troops and dismay those of Licinius.
It was first used by the Roman emperor Constantine the Great.
Since the vexillum consisted of a flag suspended from the crossbar of a cross, it was ideally suited to symbolize the crucifixion of Christ.
" At first he was unsure of the meaning of the apparition, but the following night he had a dream in which Christ explained to him that he should use the sign against his enemies.
Eusebius then continues to describe the labarum, the military standard used by Constantine in his later wars against Licinius, showing the Chi-Rho sign.