The Labarum of [[Constantine the Great|Constantine]] was a [[w:Vexillum|vexillum]]<ref group="note">The [[w:Vexillum|vexillum]] (plural vexilla) was a military standard (flag, banner) used in the Classical Era of the Roman Empire. On the vexillum the cloth was draped from a horizontal crossbar suspended from the staff; this is unlike most modern flags in which the 'hoist' of the cloth is attached directly to the vertical staff. The bearer of a vexillum was known as a ''vexillarius''. The vexillum was a treasured symbol of the military unit that it represented and it was closely defended in combat.</ref> that displayed the "[[w:Chi Rho|Chi-Rho]]" [[w:Christogram|Christogram]], formed from the first two Greek letters of the word "[[Jesus Christ|Christ]]" (Greek: '''ΧΡ'''ΙΣΤΟΣ, or '''Χρ'''ιστός) — [[w:Chi (letter)|Chi]] (χ) and [[w:Rho (letter)|Rho]] (ρ). Fashioned after legionary standards, it substituted the form of a [[cross]] for the old pagan symbols, and was surmounted by a jewelled wreath of gold containing the monogram of Christ, intersecting '''Chi''' (χ) and '''Rho''' (ρ); upon this hung a [[w:Tyrian purple|rich purple]] banner,<ref group="note">Purple dye at this time was a rarity derived from a shellfish of the genus ''[[w:Murex|Murex]].'' [[w:Tyrian purple|Tyrian purple]] ((Greek, πορφύρα, porphyra, Latin: purpura), also known as royal purple, imperial purple) was prized by the Romans, who used it to colour ceremonial robes.</ref> beset with gold trim and profuse embroidery. The inscription ''' ''"Εν Τουτω Νικα"'' (''In Hoc Signo Vinces'') — "In this sign, conquer" ''' was in all probability inscribed upon the actual standard, although [[Eusebius of Caesarea|Eusebius]] mentions that royal portraits of Constantine and his children were integrated.<ref group="note">These portraits could have been embroidered, or set as [[w:Phalera (military decoration)|medallions/roundels]] on the staff. Later, the name ''Labarum'' was given to variants of the original standard. An idea of some of the deviations in form of the standards furnished to different divisions of the army may be obtained from several coins of Constantine's reign that are still preserved. On one coin, for instance, the portraits of the emperor and his sons are represented on the actual banner (instead of as [[w:Phalera (military decoration)|medallions/roundels]] on the staff); on a second, the banner is inscribed with the Chi-Rho monogram, and surmounted by the equal-armed [[cross]] while the medallions/roundels of the royal portraits, are on the shaft below the banner. ("[http://oce.catholic.com/index.php?title=Labarum Labarum]."'' '''Original Catholic Encyclopedia).'''</ref> St. [[Ambrose of Milan]] later wrote that the Labarum was [[Consecration of a church|consecrated]] by the Name of [[Jesus Christ|Christ]].<ref>[[Ambrose of Milan]]. ''"Letter XL."'' '''St. Ambrose Selected Letters'''.</ref>