Legions of Trajans Dacian wars

[diegis]

Actually I think Bennett suggests that the force Trajan led into Parthia was the largest ever - he estimates 17 legions, if I remember correctly. This too seems an incredible figure!

I am pretty sure i remember Bennett said that the army assembled for war against Dacians was the largest ever. However i read it quite long ago. I doubt as well the number of 17 legions against Parthia (i read numbers around 11 legions, or 100,000-120,000 soldiers for that invasion).

For ex. Sarmizegetusa, the Dacian capital, was at no more then 200 kilometers i think, from Roman border of Moesia (which was close to core of the empire). A rather short distance for a logistic supply line, even for a large force, even in mountain areas and conditions. Compare this with much large desert areas in Parthia with much longer supply lines needed.

If we assume each of the four main legions was at full strength (unlikely), that gives 20800 legionary troops. Supported by four or so vexillations of about 1000 men each from other legions brings this figure to 24800. Adding three Trajanic (double sized) Praetorian cohorts adds another 3000 men (27800), and a matching force of auxiliaries would bring the maximum total army strength to 55600 men.

That in itself is a very significant force! The logistics alone for such an army in the field would be formidable. But it's substantially less than the figures quoted above, in their hundreds of thousands.

Nobody doubts that the Dacian wars were both long and hard, or that the Dacians were a considerable threat to the Danube frontier. But there is no need, I would say, to vastly inflate the figures on the Roman side to illustrate this. It has been said that Caesar used ten legions to conquer Gaul - but in the Imperial era the legions were supported by their own number of trained and well equipped auxiliaries: if Caesar had these troops at his disposal he perhaps would only have needed five legions!

- Nathan

Hmm, wasnt 6000 (or 5800) soldiers for a legion? And i am pretty sure legions was in full number, as Trajan prepared several years for the war

So if we took that 13 legion + a close number of auxiliars + quite many irregular troops (mercenaries rised just for this wars and disbanded after, as probably those Germanic ones present on the Column) we get a number around those 150,000 - 175,000 - 200,000 (agree, last one sound a bit exagerated but was mentioned too) mentioned previously.

Just if we look at engineering works we saw that required huge resources and manpower. A channel was dig to divert a big part of Danube (who is quite a large river), and Appollodor construct in couple years the largest bridge in the world (for at least a millenium). And all fortresses in Moesia was reinforced or rebuild in stone. All this was done by legionars i think (not sure if auxiliares participate to such engineering works too) in few years, legionars who participated to war too, so i really doubt was just 20,000 or 25,000 of them.

And most of the Roman troops massed in Moesia participated in invasion in Dacia, because after the battle of Tapae (one from 101 AD) Dacians managed to slow down the Roman advance and Decebalus ordered a counterattack in Moesia during the winter of 101/102, trying probably to cut the Roman logistic lines and leave the invasion army isolated in the mountains during harsh winter time.

Dacians are depicted assaulting Roman fortresses with battering rams and archers, so Trajan left behind just a small number of troops with garrison duties who was not able to give a battle in open field to Dacian invasion force.

Trajan himself was forced to retreat with a part of his army from Dacia, and quite rushing, he is depicted riding a horse in front of his troops and Roman cavalry is the one who intervene first defeating Sarmatian cavalry (who apear in 2 scenes on the Column). Romans was lucky that Danube didnt froze as usualy during winter, and used boats to move quickly this troops to resolve the problems in Moesia.