Each tactical unit in the imperial army, from centuria upwards, had its own standard. This consisted of a pole with a variety of adornments that was borne by dedicated standard-bearers who normally held the rank of duplicarius. Military standards had the practical use of communicating to unit members where the main body of the unit was situated, so that they would not be separated, in the same way that modern tour-group guides use umbrellas or flags. But military standards were also invested with a mystical quality, representing the divine spirit (genius) of the unit and were revered as such (soldiers frequently prayed before their standards). The loss of a unit's standard to the enemy was considered a terrible stain on the unit's honour, which could only be fully expunged by its recovery.

The standard of a centuria was known as a signum, which was borne by the unit's signifer. It consisted of a pole topped by either an open palm of a human hand or by a spear-head. The open palm, it has been suggested, originated as a symbol of the maniple (manipulus = "handful"), the smallest tactical unit in the Roman army of the mid-Republic . The poles were adorned with two to six silver discs (the significance of which is uncertain). In addition, the pole would be adorned by a variety of cross-pieces (including, at bottom, a crescent-moon symbol and a tassel). The standard would also normally sport a cross-bar with tassels.

The standard of a Praetorian cohort or an auxiliary cohort or ala was known as a vexillum or banner. This was a square flag, normally red in colour, hanging from a crossbar on the top of the pole. Stitched on the flag would be the name of the unit and/or an image of a god. An exemplar found in Egypt bears an image of the goddess Victory on a red background. The vexillum was borne by a vexillarius. A legionary detachment (vexillatio) would also have its own vexillum. Finally, a vexillum traditionally marked the commander's position on the battlefield.^[194] The exception to the red colour appears to have been the Praetorian Guard, whose vexilla, similar to their clothing, favoured a blue background.

From the time of Marius (consul 107 BC), the standard of all legions was the aquila ("eagle"). The pole was surmounted by a sculpted eagle of solid gold, or at least gold-plated silver, carrying thunderbolts in its claws (representing Jupiter , the highest Roman god. Otherwise the pole was unadorned. No exemplar of a legionary eagle has ever been found (doubtless because any found in later centuries were melted down for their gold content). The eagle was borne by the aquilifer, the legion's most senior standard-bearer. So important were legionary eagles as symbols of Roman military prestige and power, that the imperial government would go to extraordinary lengths to recover those captured by the enemy. This would include launching full-scale invasions of the enemy's territory, sometimes decades after the eagles had been lost e.g. the expedition in 28 BC by Marcus Licinius Crassus against Genucla (Isaccea, near modern Tulcea , Rom., in the Danube delta region), a fortress of the Getae , to recover standards lost 33 years earlier by Gaius Antonius , an earlier proconsul of Macedonia . Or the campaigns of AD 14-17 to recover the three eagles lost by Varus in AD 6 in the Teutoburg Forest .

Under Augustus, it became the practice for legions to carry portraits (imagines) of the ruling emperor and his immediate family members. An imago was usually a bronze bust carried on top of a pole like a standard by an imaginifer.

From around the time of Hadrian (r. 117-38), some auxiliary alae adopted the dragon-standard (draco) commonly carried by Sarmatian cavalry squadrons. This was a long cloth wind-sock attached to an ornate sculpture of an open dragon's mouth. When the bearer (draconarius) was galloping, it would make a strong hissing-sound.

Decorations

The Roman army awarded a variety of individual decorations (dona) for valour to its legionaries. Hasta pura was a miniature spear; phalerae were large medal-like bronze or silver discs worn on the cuirass; armillae were bracelets worn on the wrist; and torques were worn round the neck, or on the cuirass. The highest awards were the coronae ("crowns"), of which the most prestigious was the corona civica, a crown made oak-leaves awarded for saving the life of a fellow Roman citizen in battle. The most valuable award was the corona muralis, a crown made of gold awarded to the first man to scale an enemy rampart. This was awarded rarely, as such a man hardly ever survived.

There is no evidence that auxiliary common soldiers received individual decorations like legionaries, although auxiliary officers did. Instead, the whole regiment was honoured by a title reflecting the type of award e.g. torquata ("awarded a torque") or armillata ("awarded bracelets"). Some regiments would, in the course of time, accumulate a long list of titles and decorations e.g. cohors I Brittonum Ulpia torquata pia fidelis c.R..

Flavius Julius Constans (320-350) was a Roman Emperor who ruled from 337 until his death. Constans was the third and youngest son of Constantine the Great and Fausta , Constantine's second wife.

On 25 December 333 Constantine elevated Constans to Caesar.

In 337 he succeeded his father, jointly with his older brothers Constantine II and Constantius II , receiving Italy , Pannonia and Africa as his portion. Constantine II, who ruled over Gaul, Spain and Britain, attempted to take advantage of his youth and inexperience by invading Italy in 340, but Constans defeated Constantine at Aquileia , where the older brother died. The invasion was the effect of brotherly tensions between the two emperors. Constantine II was, at first, Constans's guardian. As Constans grew older, Constantine II never relinquished that position.

In 341-2, Constans led a successful campaign against the Franks and in the early months of 343 visited Britain . The source for this visit, Julius Firmicus Maternus , does not give a reason for this but the quick movement and the danger involved in crossing the channel in the dangerous winter months, suggests it was in response to a military emergency of some kind, possibly to repel the Picts and Scots .

Regarding religion, Constans was tolerant of Judaism but promulgated an edict banning pagan sacrifices in 341. He suppressed Donatism in Africa and supported Nicene orthodoxy against Arianism , which was championed by his brother Constantius the latter. Constans called the Council of Sardica , which unsuccessfully tried to settle the conflict.

In 350, the general Magnentius declared himself emperor with the support of the troops on the Rhine frontier, and later the entire Western portion of the Roman Empire. Constans lacked any support beyond his immediate household, and was forced to flee for his life. Magnentius' supporters cornered him in a fortification in Helena, southwestern Gaul, where he was killed by Magnentius's assassins.