and the two Eastern comitatus in the vicinity of Constantinople. Regiments The changes to unit structure in the 4th century were reduction of unit sizes and increase in unit numbers, establishment of new unit types and establishment of a hierarchy of units more complex than the old one of legions and auxilia. Unit sizes The evidence for the strength of late army units is very fragmented and equivocal. The table below gives some recent estimates of unit strength, by unit type and grade: *Scholares were not technically comitatenses ** Vexillatio units could be named "Equites" e.g. Equites Stablesiani Much uncertainty remains, especially regarding the size of limitanei regiments, as can be seen by the wide ranges of the size estimates. It is also possible, if not likely, that unit strengths changed over the course of the 4th century. For example, it appears that Valentinian I split about 150 comitatus units with his brother and co-emperor Valens. The resulting units may have been just half the strength of the parent units (unless a major recruitment drive was held to bring them all up to original strength). Scholae are believed to have numbered c. 500 on the basis of a 6th-century reference. In the comitatus, there is consensus that vexillationes were c. 500 and legiones c. 1,000 strong. The greatest uncertainty concerns the size of the crack auxilia palatina infantry regiments, originally formed by Constantine. The evidence is contradictory, suggesting that these units could have been either c. 500 or c. 1,000 strong, or somewhere in between. If the higher figure were true, then there would be little to distinguish auxilia from legiones, which is the strongest argument in favour of c. 500. For the size of limitanei units, opinion is divided. Jones and Elton suggest from the scarce and ambiguous literary evidence that border legiones numbered c. 1,000 men and that the other units contained in the region of 500 men each. Others draw on papyrus and more recent archaeological evidence to argue that limitanei units probably averaged about half the Jones/Elton strength i.e. c. 500 for legiones and around 250 for other units. Unit types Scholae Despite existing from the early 4th century, the only full list of scholae available is in the Notitia, which shows the position at the end of the 4th century/early 5th century. At that time, there were 12 scholae, of which 5 were assigned to