Laudator Temporis Acti

Carl H. Kraeling, "The Episode of the Roman Standards at Jerusalem," Harvard Theological Review 35.4 (October, 1942) 263-289 (at 269-270):

The word σημαία used by Josephus in his account of the episode of the standards is, like its Latin equivalent signum, a generic term and may apply to any or all of the standards borne by military units, though it is used also in a narrower sense for one particular type. Among the Roman standards the first to be mentioned are the aquila, a golden eagle mounted on a pole, and the imago or imagines, representations of animals or busts of the Emperor similarly mounted.¹³ Both types are essentially symbolic and religious in their significance. The aquila borne by the aquilifer is the palladium exclusively of the legion. Legions also have imagines borne by imaginiferi, but they share this type of standard with other troops, the urbaniciani, the vigiles, the alae and the auxiliarii. The theriomorphic imagines, comprising mainly zodiacal animals, have something to do with the dies natalis of the unit. The images of the Emperor, what ever else they may denote, have a religious and cultic significance also. While every established military unit could, and perhaps did, have its own theriomorphic imago, it is clear that some units did not have separate representations of the Emperor. What the criterion for the distribution of the imperial likenesses may be, is not yet entirely evident.

The next type of standard to be mentioned is that to which the word signum is applied in the narrower sense.¹⁴ More familiar than the others if for no other reason than because of representations in the school texts of Caesar's Gallic Wars, the signum consists of a spear decorated just below the spear-head with a cross-bar and fillets, and adorned along the shaft with a series of discs, or wreaths and discs, or wreaths and discs and mural crowns. So far as the discs (phalerae) are concerned the signa can be divided into two types, those that are aniconic and have smooth, polished surface, and those that are iconic, being embossed with a likeness of an emperor (or an image of a deity?). The signa, while also of religious significance, are basically the instruments of tactical procedure and hence essential to all troops engaged in tactical manoeuvres. Each military unit has as many signa as it has tactical elements, though in the case of a cohort the signum of the triarii maniple is simultaneously also the signum of the cohort as a whole.

The last type of standard to be mentioned is the vexillum, a cloth flag attached to a cross-bar hanging from the top of a pole or spear. It is used by temporary detachments from established military units, which are therefore known as vexillationes, and in cavalry alae. Under what conditions it served as an identifying medium and as a tactical instrument respectively, is not entirely clear.

¹³ On the general subject of standards cf. A.J. Reinach in Daremberg-Saglio, s.v. signa; A. v. Domaszewski, Die Fahnen im Römischen Heere, Abhandlungen des archäologisch-epigraphischen Seminares der Universität Wien, Vol. V, 1885; and Kromayer-Veith, op. cit., esp. pp. 402 ff., 520 ff.

¹⁴ To avoid confusion we shall use the term signum here wherever this particular type of standard is meant, keeping "standard" as the generic term throughout.