A vexillation was a temporary grouping of troops from (usually) disparate units for a specific purpose, so it could be any size, depending on that purpose. Sometimes they would be used to reinforce an army with specialist troops, or provide legionary reinforcements without transferring an entire legion; other times, less frequently maybe, they would operate independently. A few examples of vexillations:
Vexillatio legionis X Fretensis (Caesarea Maritima AE 1972, 00670) - a single detachment of the tenth legion, sent to Caesarea, maybe from the main legion base at Jerusalem. The inscription might indicate that they were involved in building work, and left their name on the result.
Vexillationum legionum V Macedonicae et XI Claudiae in Germanica expeditione (Rome CIL 06,01477) - detachment drawn from two legions in Lower Moesia for a military campaign in Germany. Commanded by a dux. The campaign in question could have drawn vexillations from the various legions on the Danube.
Vexillatio sagittariorum exercitus Syriaci (Carnuntum, Pannonia AE 1896, 00027) - detachment of archers from the army of Syria, presumably intended to reinforce a campaigning army on the Danube. These would have been auxiliaries: Syria was known for its archers, so if Pannonia needed a lot of missile troops, Syria was a good place to get them! None of these inscriptions, unfortunately, tell us how many men were in the vexillation...
Vexillationibus equitum electorum alarum praetoriae Augustae Syriacae Agrippianae Herculianae singularium item cohortium I Lucensium II Ulpiae equitatae civium Romanorum I Flaviae civium Romanorum I Thracum III Ulpiae Paflagonum II equitum I Ascolitarum Felicis V Chalcidenorum V Petraeorum IIII Lucensium I Ulpiae Petraeorum II Ulpiae Paflagonum I Ulpiae sagittariorum III Dacorum I Syngambrum (Gradista, CIL 03,0600) - this is a huge auxiliary vexillation (4 cavalry alae, 13 infantry cohorts) drawn from the army on the Danube and commanded in a Mesopotamian war by the Praepositus Marcus Valerius Lollianus. The war was probably that of Lucius Verus 162-66, and Lollianus' force could either have operated on its own as a sort of 'battle group', or have been broken up to reinforce the other parts of the main army in Mesopotamia. Lollianus himself was an equestrian, and had completed the three stages of the equestrian military career before becoming praepositus of this force.
Vexillationum legionum VIIII I Adiutricis II Adiutricis II Augustae VIII Augustae VIIII Hispanae XIIII Geminae XX Victricis XXI Rapacis (AE 1903, 00368) - and this one's a big legionary vexillation, commanded by Praefectus Vexillariorum Caius Velius Rufus. Rufus was another career officer, who rose from centurion to procurator under the Flavians. His vexillation comprises bits of nine legions (although one of them is missing from the list) - unfortunately we don't have an exact date for it, or a purpose (Domitian's Chattian war has been suggested). Even if only a single cohort was drawn from each of the legions, the force would almost be the strength of a full legion. Once again, though, the actual size isn't given.
That smaller, apparently independent legion detachments were possible is suggested by the career of L. Roscius Aelianus Maecius Celer, senatorial tribune of IX Hispana, who was sent on a German expedition at some point (CIL 14,03612). Since the ninth legion were probably in Britain at this point, and could well have been engaged in the campaign under Agricola, the vexillation was perhaps not too large - two to four cohorts at most. Celer was a relatively senior officer, and would perhaps not have served under an equestrian praepositus commanding a larger detachment.
Finally, this is an interesting one:
Vexillationis felicissimae expeditionis urbicae itemque Asianae adversus hostes publicos (AE 1966, 00495) - the 'felicitious expedition to the city' was Severus' march on Rome in AD193, and that against the 'public enemies in Asia' was the war against Pescennius Niger the following year. This vexillation, again drawn from the Danubian army, seems to have consisted mainly of cavalry; the commander was Lucius Valerius Valerianus, who led the vanguard of the army into Italy and later, according to Dio (74.7.1-8), led a flanking cavalry attack that decided the battle of Cilician Gates. He also fought at Issus, again leading the cavalry, and later in the Mesopotamian expedition. Valerianus' vexillation, therefore, was clearly an independent cavalry force.
- Nathan
Nathan Ross
