Aquila ( Roman ) An aquila , or eagle , was the standard of a Roman legion . A legionary known as an aquilifer , or eagle - bearer , carried this standard . Each legion carried one eagle . The eagle was extremely important to the Roman military , beyond merely being a symbol of a legion . A lost standard was considered an extremely grave occurrence , and the Roman military often went to great lengths to both protect a standard and to recover it if lost ; for example , see the aftermath of the Battle of the Teutoburg Forest , where the Romans spent decades attempting to recover the lost standards of three legions . History . The " signa militaria " were the Roman military ensign s or standard s . The most ancient standard employed by the Romans is said to have been a handful ( " manipulus " ) of straw fixed to the top of a spear or pole . Hence the company of soldiers belonging to it was called a " maniple " . The bundle of hay or fern was soon succeeded by the figures of animals , of which Pliny the Elder ( " H . N . " x . 16 ) enumerates five : the eagle , the wolf , the minotaur ( Festus , s . v . Minotaur . ) , the horse , and the boar . In the second consulship of Gaius Marius ( 104 BC ) the four quadrupeds were laid aside as standards , the eagle ( " Aquila " ) being alone retained . It was made of silver , or bronze , with outstretched wings , but was probably of a relatively small size , since a standard - bearer ( signifer ) under Julius Caesar is said in circumstances of danger to have wrenched the eagle from its staff and concealed it in the folds of his girdle . Under the later emperors the eagle was carried , as it had been for many centuries , with the legion , a legion being on that account sometimes called " aquila " ( Hirt . Bell . Hisp . 30 ) . Each cohort had for its own ensign the serpent or dragon , which was woven on a square piece of cloth " textilis anguis " , elevated on a gilt staff , to which a cross - bar was adapted for the purpose , and carried by the " draconarius " . Another figure used in the standards was a ball ( orb ) , supposed to have been emblematic of the dominion of Rome over the world ; and for the same reason a bronze figure of Victoria was sometimes fixed at the top of the staff , as we see it sculptured , together with small statues of Mars , on the Column of Trajan and the Arch of Constantine . Under the eagle or other emblem was often placed a head of the reigning emperor , which was to the army the object of idolatrous adoration . The name of the emperor , or of him who was acknowledged as emperor , was sometimes inscribed in the same situation . The pole used to carry the eagle had at its lower extremity an iron point ( cuspis ) to fix it in the ground , and to enable the aquilifer in case of need to repel an attack . The minor divisions of a cohort , called centuries , had also each an ensign , inscribed with the number both of the cohort and of the century . This , together with the diversities of the crests worn by the centurions , enabled each soldier to take his place with ease . In the Arch of Constantine at Rome there are four sculptured panels near the top which exhibit a great number of standards and illustrate some of the forms here described . The first panel represents Trajan giving a king to the Parthians : seven standards are held by the soldiers . The second , containing five standards , represents the performance of the sacrifice called suovetaurilia . When Constantine embraced Christianity , a figure or emblem of Christ , woven in gold upon purple cloth , was substituted for the head of the emperor . This richly ornamented standard was called " labarum " . The labarum is still used today by the Orthodox Church in the Sunday service . The entry procession of the chalice whose contents will soon become holy communion is modeled after the procession of the standards of the Roman army . Even after the adoption of Christianity as the Roman Empire ' s religion , the Aquila eagle continued to be used as a symbol . During the reign of Eastern Roman Emperor Isaac I Komnenos , the single - headed eagle was modified to double - headed to symbolise the Empire ' s dominance over East and West . Since the movements of a body of troops and of every portion of it were regulated by the standards , all the evolutions , acts , and incidents of the Roman army were expressed by phrases derived from this circumstance . Thus " signa inferre " meant to advance , " referre " to retreat , and " convertere " to face about ; " efferre " , or " castris vellere " , to march out of the camp ; " ad signa convenire " , to re - assemble . Notwithstanding some obscurity in the use of terms , it appears that , whilst the standard of the legion was properly called " aquila " , those of the cohorts were in a special sense of the term called " signa " , their bearers being " signiferi " , and that those of the manipuli or smaller divisions of the cohort were denominated " vexilla " , their bearers being " vexillarii " . Also , those who fought in the first ranks of the legion before the standards of the legion and cohorts were called " antesignani " . In military stratagems it was sometimes necessary to conceal the standards . Although the Romans commonly considered it a point of honour to preserve their standards , in some cases of extreme danger the leader himself threw them among the ranks of the enemy in order to divert their attention or to animate his own soldiers . A wounded or dying standard - bearer delivered it , if possible , into the hands of his general , from whom he had received it " signis acceptis " . Further reading . Signa Militaria " , by James Yates , in the public domain " A Dictionary of Greek and Roman Antiquities " ( pp . 1044 – 1046 ) 978 - 3 - 7954 - 2477 - 0