The name given to the banner of Emperor constantine i, an adaptation of the Roman cavalry standard (vexillum ) with the pagan emblems replaced by Christian symbols. After his victory at the Milvian bridge (313), Constantine made the labarum the imperial flag of the western Empire, and from 324, for the entire Roman Empire. It was accompanied by an honor guard of 50 soldiers, outstanding for their bravery and devotion to the Christian faith (Eusebius, Vita Constantini 1.26).
Eusebius stated that the labarum was designed by Constantine himself on the day after his alleged vision of the cross. The banner consisted of a long gilt spear with a transverse bar forming a cross, crowned with a wreath of gold and precious stones enclosing the chi-rho monogram of Christ with a square purple banner inscribed ΤΟϒΤΩ NIKA ("by this sign conquer") and embroidered with precious stones interlaced with gold hanging from the cross-bar. There were medallions of the Emperor and his sons immediately above this banner (Eusebius, Vita Constantini 1.26). The labarum is pictured on Constantinian coins from 314. Variants of the original labarum were supplied to all legions; the variety of design, together with the constancy of the essential parts, can be seen upon comparison of several preserved Constantinian coins. After a period of brief eclipse during the reign of Emperor Julian (361–363), the labarum was brought back to a place of honor by Jovian and housed in the imperial palace in Constantinople. The significance of the labarum transcends its use as the first Christian military standard. In effect it proclaimed that Constantine, aware of the bankruptcy of the old psychological stimuli to geopolitical solidarity, was calling on the labarum to provide a new stimulus and rallying point; and it meant that Christianity was agreeing to ride at the head of a huge organized military force and share the fortunes of an earthly power.
Bibliography: eusebius, Vita Constantini 1.26–31; Hist. eccl. 9.9.2. h. grÉgoire, Byzantion 4 (1927–28) 477–482. h. leclercq, Dictionnaire d'archéologie chrétienne et de liturgie, ed. f. cabrol, h. leclercq, and h. i. marrou (Paris 1907–53) 8.1:927–962. j. j. hatt, Latomus 9 (1950) 427–436.
[a. g. gibson]