Questions on Constantius, Constantine and the Northern British Tribes

[Nathan Ross]

This means that (whatever his sympathies) Constantine, at that time, was not a Christian.

Constantine's Christianity was also something of a spectrum, I think, and never very 'orthodox'! He doesn't seem to have embraced it as his sole faith until after the defeat of Licinius in 324 (based on his coinage), but he was certainly very sympathetic to it, at least, before that. His killing of the Frankish chiefs in c307-8 in the arena at Trier (and the similar slaying of a large number of Frankish prisoners at or around the same time) might seem unChristian, but the later Roman state continued to use savage executions even after the ban on gladiatorial combat (which probably dates to c.325).

You might find this thread, on the Christianisation of Constantine and his successors, interesting:

Christianity and the Late Roman Empire

What would these forces have numbered?

There's a paper by Simon James ('Britain and the Late Roman Army', in Military and Civilian in Roman Britain, BAR) that discusses army numbers in Britain in the 4th century. Calculating the numbers of units listed in the Notitia Dignitatum, Jones arrives at a figure of 33,500. However, he says, the long period of peace in 3rd century Britain saw the province used as a source of manpower (the Aurelius Cervianus phalera appears to show a joint detachment of II Aug and XX VV operating on the continent), and successive drafts of men for the continental armies were probably never replaced, leaving most units severely depleted.

The 'real collapse in numbers', James says, was in the late 3rd century; he estimates that the garrison army of Britain could have been as low as 12000 men after that. He cites the smaller sizes of forts and barracks as evidence. It's perhaps significant that in 367 Theodosius the Elder commenced the pacification of Britain (following the 'barbarian conspiracy') with only four units of palatine auxilia, something like 2000-4000 men.

I suspect James's figure is probably overly low, but we'd have to wonder about the nature of the threat they faced. Nick Aitcheson (The Picts and the Scots at War) estimates the total population of 'Pictland' as 40-100,000, based on settlement and agricultural patterns, giving a potential military strength of only 7-10,000 warriors. Even so (and this number, again, could be too low), a general muster of such a force could pose a severe problem to a much-depleted British garrison.

The presence of Constantius himself in northern Britain in 305-6 indicates an imperial expedition, which would have included both the troops of the comitatus and almost certainly detachments of the Rhine legions as well. A note in Aurelius Victor perhaps suggests that Germanic irregular troops, under thier own king(s), may have accompanied the expedition. A task force of this nature (10,000 men might be a reasonable estimate), added to the garrison troops already in the province, would have been sufficient to counter any large-scale raiding by the Picts, and launch a powerful punitive campagn in reprisal if required.

As for the total army size in the western empire at that time, it's a bit of a guessing game. One clue might be the descriptions of Constantine's army in the invasion of Italy in 312: a panegyricist in 313 claims he had 'fewer than 40,000 men', and this was a quarter of the men he had available in the west. If we assume the number might have been 30-35,000, than Constantine's total force in Gaul, Spain, Britain and on the Rhine may have been 120-140,000 men in total. But, again, all these numbers may or may not have been highly inflated!