The Dacians: Rome\'s Greatest Enemy?

[Nathan Ross]

So yes 2 legions is a large army!

It is. If we can assume an equal number of auxiliaries (not certain, but a good bet), then the force could number 20,000. No paltry number of men.

Besides, a provincial governor, in normal circumstances, could only command the legions based in his own province. Oppius Sabinus ruled a united Moesia, so had four legions at his disposal - but he was surprised by a raid across the Danube and would probably only have been able to summon two of them at most to meet the threat.

Fuscus, as an equestrian, was officially not permitted to lead legions at all! Quite possibly his army was made up of vexillations of a number of different legions supported by praetorian cohorts. Alternatively, given a special command, he could have led the two legions of Moesia Superior with detachments of others. Tettius Julianus was governor of the (divided) Moesia Superior, so had two legions - but his army, again, probably included strong detachments of others.

If these seem small, it's worth comparing them to other attested non-imperial field forces of the period (attested in sources, that is, not modern conjecture): Varus in Germany in AD9 had 3 legions, Germanicus had 4 (although 8 at his final battle), Plautius invaded Britain with 4, Corbulo had 3 plus a vexillation in Armenia in AD58, Paulinus had 1 plus a vexillation against Boudica in AD61, Vespasian had 4 in Judea, Paetus led 2 into Armenia, Agricola led a maximum of 4 into north Britain (although he only had c.20,000 men with him at the final battle), Arrian planned to lead 2 against the Alans, and so on. 2-4 legions appears to have been quite the norm for provincial offensive operations. If the emperor himself was in charge, of course, the number could increase - but few reliable sources I can find mention more than 8-10 legions total.